U.S. patent application number 11/588046 was filed with the patent office on 2007-07-19 for intelligent life testing methods and apparatus for leakage current protection.
This patent application is currently assigned to General Protecht Group, Inc.. Invention is credited to Wusheng Chen, Fu Wang, Lianyun Wang.
Application Number | 20070164750 11/588046 |
Document ID | / |
Family ID | 36907533 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070164750 |
Kind Code |
A1 |
Chen; Wusheng ; et
al. |
July 19, 2007 |
INTELLIGENT LIFE TESTING METHODS AND APPARATUS FOR LEAKAGE CURRENT
PROTECTION
Abstract
An apparatus for testing the life of a leakage current
protection device having a leakage current detection circuit. In
one embodiment, the apparatus a trip mechanism state generator, a
fault alarm generator, a ground fault simulation unit. In
operation, the ground fault simulation unit generates a simulated
ground fault signal during every positive half-wave of an AC power,
the simulated ground fault signal is detected by the leakage
current detection circuit, the leakage current detection circuit
responsively generates a signal to turn a switching device into its
conductive state so as to allow a current to pass therethrough, the
passed current is converted into a DC voltage in accordance with a
trip mechanism state generated by the trip mechanism state
generator, the fault alarm circuit receives and analyzes the DC
voltage and indicates whether a fault exists in the leakage current
protection device.
Inventors: |
Chen; Wusheng; (Yueqing
Zhejiang, CN) ; Wang; Fu; (Yueqing Zhejiang, CN)
; Wang; Lianyun; (Yueqing Zhejiang, CN) |
Correspondence
Address: |
MORRIS MANNING MARTIN LLP
3343 PEACHTREE ROAD, NE, 1600 ATLANTA FINANCIAL CENTER
ATLANTA
GA
30326
US
|
Assignee: |
General Protecht Group,
Inc.
Yueqing
CN
|
Family ID: |
36907533 |
Appl. No.: |
11/588046 |
Filed: |
October 26, 2006 |
Current U.S.
Class: |
324/527 |
Current CPC
Class: |
G01R 31/3278 20130101;
G01R 31/52 20200101; H02H 3/335 20130101 |
Class at
Publication: |
324/527 |
International
Class: |
G01R 31/08 20060101
G01R031/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 2005 |
CN |
200510132772.1 |
Claims
1. An apparatus for testing the life of a leakage current
protection device, wherein the leakage current protection device
has a first inductive coil N1, a second inductive coil N2, a first
input, a second input, a first output electrically coupled to the
second input through the first inductive coil N1 and the second
inductive coil N2, a second output, a third output, a trip switch
SW101 having two LINE terminals and electrically coupled to the
first input and the second input, respectively, for receiving an AC
power, and two LOAD terminals and electrically coupled to the
inputs of an electrical appliance, respectively, a power supply
circuit having an input electrically coupled to the first input,
and an output electrically coupled to the second output, a trip
coil circuit having a switching device VD1 having a gate, an anode
and a cathode, an input, an output electrically coupled to the
third output, and a leakage current detection circuit having an
output electrically coupled to the input of the trip coil circuit,
and a power supply inputp electrically coupled to the output of the
power supply circuit and the second output, comprising: (i) a trip
mechanism state generator having a first input electrically coupled
to the third output of the leakage current protection device, a
second input electrically coupled to the first input of the leakage
current protection device, a third input electrically coupled to
the second input of the leakage current protection device, a first
output and a second output, wherein the trip mechanism state
generator is adapted for generating a trip mechanism state at the
first output and the second output, wherein the trip mechanism
state has a first state and a second state, and wherein when the
trip mechanism state is in the first state, there is no fault exist
in the leakage current protection device, and wherein the trip
mechanism state is in the second state, there is at least one fault
exists in the leakage current protection device; (ii) a fault alarm
generator having a first input electrically coupled to the first
output of the trip mechanism state generator, a second input
electrically coupled to the second output of the trip mechanism
state generator, and a power supply input electrically coupled to
the second output of the leakage current protection device; and
(iii) a ground fault simulation unit having an input electrically
coupled to the first input of the leakage current protection
device, and an output electrically coupled to the first output of
the leakage current protection device, wherein, in operation, the
ground fault simulation unit generates a simulated ground fault
signal during every positive half-wave of the AC power, the
simulated ground fault signal is detected by the leakage current
detection circuit, the leakage current detection circuit
responsively generates a signal to turn the switching device VD1
into its conductive state so as to allow a current to pass
therethrough, the passed current is converted into a DC voltage in
accordance with a trip mechanism state generated by the trip
mechanism state generator, the fault alarm circuit receives and
analyzes the DC voltage and indicates whether a fault exists in the
leakage current protection device.
2. The apparatus of claim 1, wherein the trip mechanism state
generator comprises: (i) a first diode D1 having a cathode and an
anode electrically coupled to the second input of the trip
mechanism state generator; (ii) a second diode D2 having a cathode
electrically coupled to the cathode of the first diode D1 and the
first input of the trip mechanism state generator, and an anode
electrically coupled to the third input of the trip mechanism state
generator; (iii) a third diode D3 having an anode and a cathode
electrically coupled to the second input of the leakage current
protection device and the anode of the second diode D2; (iv) a
fourth diode D4 having a cathode electrically coupled to the anode
of the first diode D1 and the first input of the leakage current
protection device, and an anode electrically coupled to a first
output of the trip mechanism state generator; (v) a fifth resistor
R5 having a first terminal electrically coupled to the first output
of the trip mechanism state generator, and a second terminal
electrically coupled to the second output; and (vi) a sixth
resistor R6 having a first terminal electrically coupled to the
second terminal of the fifth resistor R5 and the second output of
the trip mechanism state generator, and a second terminal
electrically coupled to the anode of the third diode D3.
3. The apparatus of claim 2, the DC voltage is detected at the
first terminal and the second terminal of the resistor R5.
4. The apparatus of claim 3, wherein the DC voltage is a negative
voltage if there is no fault in the leakage current protection
device, and wherein the DC voltage is a positive voltage if there
is at least one fault in the leakage current protection device.
5. The apparatus of claim 4, wherein the fault alarm circuit
comprises a multi-vibrator having a light emitting diode (LED) D8,
wherein the multi-vibrator generates no vibration indicating that
there is no fault in the leakage current protection device when the
fault alarm circuit receives a negative DC voltage, and wherein the
multi-vibrator generates vibrations and a visible alarm through the
LED D8 indicating that there is at least one fault in the leakage
current protection device when the fault alarm circuit receives a
positive DC voltage.
6. The apparatus of claim 5, wherein the fault alarm circuit
comprises an audio alarm circuit for generating an audible
alarm.
7. The apparatus of claim 1, wherein the ground fault simulation
unit comprises: (i) a first resistor R1 having a first terminal and
a second terminal; (ii) a second resistor R2 having a first
terminal and a second terminal; (iii) a third resistor R3 having a
first terminal and a second terminal; (iv) a seventh diode D7
having a cathode and an anode, wherein the anode of the seventh
diode D7 is connected to the input that is electrically coupled a
hot wire of the AC power, and the cathode of the seventh diode D7
is connected to both the first terminal of the resistor R1 and the
first terminal of the second resistor R2; (iv) a first transistor
Q1 having a first collector electrically coupled to the second
terminal of the first resistor R1, a first emitter electrically
coupled to both the second terminal of the third resistor R3 and
the output, and a first base; and (iii) a sixth zener diode D6
having an anode electrically coupled to the base of the first
transistor Q1, and a cathode electrically coupled to both the
second terminal of the second resistor R2 and the first terminal of
the third resistor R3.
8. The apparatus of claim 1, wherein the ground fault simulation
unit comprises: (i) a first resistor R1 having a first terminal and
a second terminal; (ii) a second resistor R2 having a first
terminal and a second terminal; (iii) a third resistor R3 having a
first terminal and a second terminal electrically coupled to the
second output2; (iv) a seventh diode D7 having an anode
electrically coupled to the input of the ground fault simulation
unit, and a cathode electrically coupled to both the first terminal
of the first resistor R1 and the first terminal of the second
resistor R2; (v) a first transistor Q1 having a first collector
electrically coupled to the second terminal of the first resistor
R1, a first emitter electrically coupled to the second input of the
leakage current protection device, and a base; and (iv) a sixth
zener diode D6 having an anode electrically coupled to the base of
the first transistor Q1, and a cathode electrically coupled to both
the second terminal of the second resistor R2 and the first
terminal of the third resistor R3.
9. The apparatus of claim 1, wherein the ground fault simulation
unit comprises: (i) a first resistor R1 having a first terminal and
a second terminal; (ii) a seventh diode D7 having an anode
electrically coupled to the input, and a cathode electrically
coupled to the first terminal of the resistor R1; and (ii) a
transformer T1 having a primary winding having a first primary
terminal P1 and a second primary terminal P2, and a secondary
winding having a first secondary terminal S1 and a second secondary
terminal S2, wherein the first primary terminal P1 is electrically
coupled to the second terminal of the first resistor R1, the second
primary terminal P2 is electrically coupled to the second input of
the leakage current protection device, the first secondary terminal
S1 is electrically coupled to the second secondary terminal S2
through the first inductive coil N1 and the second inductive coil
N2.
10. The apparatus of claim 1, wherein the ground fault simulation
unit comprises: (i) a seventh diode D7 having a cathode and an
anode electrically coupled to the input; and (ii) a first resistor
R1 having a first terminal electrically coupled to the cathode of
the seventh diode D7, and a second terminal electrically coupled to
the output.
11. The apparatus of claim 1, wherein the ground fault simulation
unit comprises: (i) a first resistor R1 having a first terminal and
second terminal; (ii) a seventh diode D7 having an anode
electrically coupled to the input, and a cathode electrically
coupled to the first terminal of the first resistor R1; and (iii) a
sixth zener diode D6 having a cathode electrically coupled to the
second terminal of the first resistor R1, and an anode electrically
coupled to the output.
12. A method for intelligently testing the life of a leakage
current protection device, wherein the leakage current protection
device has a first inductive coil N1, a second inductive coil N2, a
first input, a second input, a first output electrically coupled to
the second input through the first inductive coil N1 and the second
inductive coil N2, a second output, a third output, a trip switch
SW101 having two LINE terminals and electrically coupled to the
first input and the second input, respectively, for receiving an AC
power, and two LOAD terminals and electrically coupled to the
inputs of an electrical appliance, respectively, a power supply
circuit having an input electrically coupled to the first input,
and an output electrically coupled to the second output, a trip
coil circuit having a switching device VD1 having a gate, an anode
and a cathode, an input, an output electrically coupled to the
third output, and a leakage current detection circuit having an
output electrically coupled to the input of the trip coil circuit,
and a power supply inputp electrically coupled to the output of the
power supply circuit and the second output, comprising the steps
of: (i) providing a testing device having: (a) a trip mechanism
state generator having a first input electrically coupled to the
third output of the leakage current protection device, a second
input electrically coupled to the first input of the leakage
current protection device, a third input electrically coupled to
the second input of the leakage current protection device, a first
output and a second output, wherein the trip mechanism state
generator is adapted for generating a trip mechanism state at the
first output and the second output, wherein the trip mechanism
state has a first state and a second state, and wherein when the
trip mechanism state is in the first state, there is no fault exist
in the leakage current protection device, and wherein the trip
mechanism state is in the second state, there is at least one fault
exists in the leakage current protection device; (b) a fault alarm
generator having a first input electrically coupled to the first
output of the trip mechanism state generator, a second input
electrically coupled to the second output of the trip mechanism
state generator, and a power supply input electrically coupled to
the second output of the leakage current protection device; and (c)
a ground fault simulation unit having an input electrically coupled
to the first input of the leakage current protection device, and an
output electrically coupled to the first output of the leakage
current protection device, (ii) generating a simulated ground fault
signal during every positive half-wave of the AC power by the
ground fault simulation unit; (iii) detecting the simulated ground
fault signal at the leakage current detection circuit; (iv)
generating a signal to turn the switching device VD1 into its
conductive state so as to allow a current to pass therethrough; (v)
generating a DC voltage in responsive to a trip mechanism state at
the trip mechanism state generator, wherein the trip mechanism
state is in a first state that there is no fault exist in the
leakage current protection device, or in a second state that there
is at least one fault exists in the leakage current protection
device; (vi) receiving the DC voltage at the fault alarm circuit;
and (vii) indicating whether at least one fault exists in the
leakage current protection device.
13. The method of claim 12, wherein the indicating step comprises
the step of producing a visible alarm.
14. The method of claim 13, wherein the indicating step further
comprises the step of producing an audible alarm.
15. A leakage current protection device with intelligent life
testing, comprising: (I) a leakage current protection device
having: (a) a first inductive coil N1; (b) a second inductive coil
N2; (c) a first input; (d) a second input; (e) a first output
electrically coupled to the second input through the first
inductive coil N1 and the second inductive coil N2; (f) a second
output; (g) a third output; (h) a trip switch SW101 having two LINE
terminals and electrically coupled to the first input and the
second input, respectively, for receiving an AC power, and two LOAD
terminals and electrically coupled to the inputs of an electrical
appliance, respectively; (i) a power supply circuit having an input
electrically coupled to the first input, and an output electrically
coupled to the second output; (j) a trip coil circuit having a
switching device VD1 having a gate, an anode and a cathode, an
input, and an output electrically coupled to the third output; and
(k) a leakage current detection circuit having an output
electrically coupled to the input of the trip coil circuit, and a
power supply inputp electrically coupled to the output of the power
supply circuit and the second output; (II) a trip mechanism state
generator having a first input electrically coupled to the third
output of the leakage current protection device, a second input
electrically coupled to the first input of the leakage current
protection device, a third input electrically coupled to the second
input of the leakage current protection device, a first output and
a second output, wherein the trip mechanism state generator is
adapted for generating a trip mechanism state at the first output
and the second output, wherein the trip mechanism state has a first
state and a second state, and wherein when the trip mechanism state
is in the first state, there is no fault exist in the leakage
current protection device, and wherein the trip mechanism state is
in the second state, there is at least one fault exists in the
leakage current protection device; (III) a fault alarm generator
having a first input electrically coupled to the first output of
the trip mechanism state generator, a second input electrically
coupled to the second output of the trip mechanism state generator,
and a power supply input electrically coupled to the second output
of the leakage current protection device; and (IV) a ground fault
simulation unit having an input electrically coupled to the first
input of the leakage current protection device, and an output
electrically coupled to the first output of the leakage current
protection device, wherein, in operation, the ground fault
simulation unit generates a simulated ground fault signal during
every positive half-wave of the AC power, the simulated ground
fault signal is detected by the leakage current detection circuit,
the leakage current detection circuit responsively generates a
signal to turn the switching device VD 1 into its conductive state
so as to allow a current to pass therethrough, the passed current
is converted into a DC voltage in accordance with a trip mechanism
state generated by the trip mechanism state generator, the fault
alarm circuit receives and analyzes the DC voltage and indicates
whether a fault exists in the leakage current protection
device.
16. The leakage current protection device of claim 15, wherein the
trip mechanism state generator comprises: (i) a first diode D1
having an anode electrically coupled to the second input of the
trip mechanism state generator, and a cathode; (ii) a second diode
D2 having a cathode electrically coupled to the cathode of the
first diode D1 and the first input of the trip mechanism state
generator, and an anode electrically coupled to the third input of
the trip mechanism state generator; (iii) a third diode D3 having a
cathode electrically coupled to the second input of the leakage
current protection device and the anode of the second diode D2, and
an anode; (iv) a fourth diode D4 having a cathode electrically
coupled to the anode of the first diode D1 and the first input of
the leakage current protection device, and an anode electrically
coupled to a first output of the trip mechanism state generator;
(v) a fifth resistor R5 having a first terminal electrically
coupled to the first output of the trip mechanism state generator,
and a second terminal electrically coupled to the second output;
and (vi) a sixth resistor R6 having a first terminal electrically
coupled to the second terminal of the fifth resistor R5 and the
second output of the trip mechanism state generator, and a second
terminal electrically coupled to the anode of the third diode
D3.
17. The leakage current protection device of claim 16, the DC
voltage is detected at the first terminal and the second terminal
of the resistor R5.
18. The leakage current protection device of claim 17, wherein the
DC voltage is a negative voltage if there is no fault in the
leakage current protection device, and the DC voltage is a positive
voltage if there is at least one fault in the leakage current
protection device.
19. The leakage current protection device of claim 18, wherein the
fault alarm circuit comprises a multi-vibrator having a light
emitting diode (LED) D8, wherein the multi-vibrator generates no
vibration indicating there is no fault in the leakage current
protection device if the fault alarm circuit receives the negative
DC voltage, and generates a vibration and a visible alarm through
the LED D8 indicating there is at least one fault in the leakage
current protection device if the fault alarm circuit receives the
positive DC voltage.
20. The leakage current protection device of claim 19, wherein the
fault alarm circuit comprises an audio alarm circuit for generating
an audible alarm.
21. The leakage current protection device of claim 15, wherein the
ground fault simulation unit comprises: (i) a first resistor R1
having a first terminal and a second terminal; (ii) a second
resistor R2 having a first terminal and a second terminal; (iii) a
third resistor R3 having a first terminal and a second terminal;
(iv) a seventh diode D7 having a cathode and an anode, wherein the
anode of the seventh diode D7 is connected to the input that is
electrically coupled a hot wire of the AC power, and the cathode of
the seventh diode D7 is connected to both the first terminal of the
resistor R1 and the first terminal of the second resistor R2; (iv)
a first transistor Q1 having a first collector electrically coupled
to the second terminal of the first resistor R1, a first emitter
electrically coupled to both the second terminal of the third
resistor R3 and the output, and a first base; and (iii) a sixth
zener diode D6 having an anode electrically coupled to the base of
the first transistor Q1, and a cathode electrically coupled to both
the second terminal of the second resistor R2 and the first
terminal of the third resistor R3.
22. The leakage current protection device of claim 15, wherein the
ground fault simulation unit comprises: (i) a first resistor R1
having a first terminal and a second terminal; (ii) a second
resistor R2 having a first terminal and a second terminal; (iii) a
third resistor R3 having a first terminal and a second terminal
electrically coupled to the second output2; (iv) a seventh diode D7
having an anode electrically coupled to the input of the ground
fault simulation unit, and a cathode electrically coupled to both
the first terminal of the first resistor R1 and the first terminal
of the second resistor R2; (v) a first transistor Q1 having a first
collector electrically coupled to the second terminal of the first
resistor R1, a first emitter electrically coupled to the second
input of the leakage current protection device, and a base; and
(iv) a sixth zener diode D6 having an anode electrically coupled to
the base of the first transistor Q1, and a cathode electrically
coupled to both the second terminal of the second resistor R2 and
the first terminal of the third resistor R3.
23. The leakage current protection device of claim 15, wherein the
ground fault simulation unit comprises: (i) a first resistor R1
having a first terminal and a second terminal; (ii) a seventh diode
D7 having an anode electrically coupled to the input, and a cathode
electrically coupled to the first terminal of the resistor R1; and
(ii) a transformer T1 having a primary winding having a first
primary terminal P1 and a second primary terminal P2, and a
secondary winding having a first secondary terminal S1 and a second
secondary terminal S2, wherein the first primary terminal P1 is
electrically coupled to the second terminal of the first resistor
R1, the second primary terminal P2 is electrically coupled to the
second input of the leakage current protection device, the first
secondary terminal S1 is electrically coupled to the second
secondary terminal S2 through the first inductive coil N1 and the
second inductive coil N2.
24. The leakage current protection device of claim 15, wherein the
ground fault simulation unit comprises: (i) a seventh diode D7
having a cathode and an anode electrically coupled to the input;
and (ii) a first resistor R1 having a first terminal electrically
coupled to the cathode of the seventh diode D7, and a second
terminal electrically coupled to the output.
25. The leakage current protection device of claim 15, wherein
the-ground fault simulation unit comprises: (i) a first resistor R1
having a first terminal and second terminal; (ii) a seventh diode
D7 having an anode electrically coupled to the input, and a cathode
electrically coupled to the first terminal of the first resistor
R1; and (iii) a sixth zener diode D6 having a cathode electrically
coupled to the second terminal of the first resistor R1, and an
anode electrically coupled to the output.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority of Chinese Patent
Application No. 2005 1073 2772.1, filed on Dec. 26, 2005, entitled
"Intelligent Life Testing Methods and Apparatus for Leakage Current
Protection" by Wusheng CHEN, Fu WANG, and Lianyun WANG, the
disclosure of which is incorporated herein by reference in its
entirety.
[0002] This application is related to four co-pending U.S. patent
applications, entitled "Intelligent Life Testing Methods and
Apparatus for Leakage Current Protection Device with Indicating
Means," by Feng ZHANG, Honigliang CHEN, Fu WANG, Wusheng CHEN,
Yulin ZHANG and Huaiyin SONG, (Attorney Docket No. 15183-54222);
"Apparatus and Methods for Testing the Life of a Leakage Current
Protection Device," by Feng ZHANG, Hongliang CHEN, Fu WANG, Wusheng
CHEN, Yulin ZHANG and Huaiyin SONG; (Attorney Docket No.
15183-54223); "Intelligent Life Testing Methods and Apparatus for
Leakage Current Protection," by Feng ZHANG, Hongliang CHEN, Fu
WANG, Wusheng CHEN, Yulin ZHANG and Huaiyin SONG; (Attorney Docket
No. 15183-54224); and "Intelligent Life Testing Methods and
Apparatus for Leakage Current Protection," by Feng ZHANG, Hongliang
CHEN, Fu WANG, Wusheng CHEN, Yulin ZHANG and Huaiyin SONG,
(Attorney Docket No. 15183-54865), respectively. The above
identified co-pending applications were filed on the same day that
this application was filed, and with the same assignee as that of
this application. The disclosures of the above identified
co-pending applications are incorporated herein by reference in
their entireties.
FIELD OF THE PRESENT INVENTION
[0003] The present invention generally relates to a leakage current
protection device, and more particularly, to an apparatus and
methods for intelligently testing the life of a leakage current
protection device.
BACKGROUND OF THE PRESENT INVENTION
[0004] Leakage current protection can be divided into two
categories according to their functionalities: ground fault circuit
interrupter (hereinafter "GFCI") and arc fault circuit interrupter
(hereinafter "AFCI"). In order to achieve the goal of leakage
current protection, a leakage current protection device used for
appliances comprises at least two components: a trip mechanism and
a leakage current detection circuit. The trip mechanism comprises a
silicon controlled rectifier (hereinafter "SCR"), trip coil, and
trip circuit interrupter device. The leakage current detection
circuit comprises induction coils, a signal amplifier and a
controller.
[0005] The operating principle of a GFCI used for appliances is as
follows. In a normal condition, the electric current on a hot wire
of an electrical socket should be the same as the electric current
on a neutral wire in the same electrical socket. When a leakage
current occurs, there exists a current differential between the hot
wire and the neutral wire of the electrical socket. The inductive
coil of the leakage current protection device monitors the current
differential and transfers the current differential into a voltage
signal. The voltage signal is then amplified by the signal
amplifier and sent to the controller. If the current differential
exceeds a predetermined threshold, the controller sends a control
signal to the trip circuit interrupter to cut off the connection
between the AC power and the appliance to prevent damage caused by
the leakage current.
[0006] For an AFCI used for appliances, in a normal condition, the
electric current on a hot wire of an electrical socket should be
the same as the electric current on a neutral wire in the same
electrical socket, and the variation of both the electric current
is same. When an arc fault occurs due to aging or damages of the
AFCI device, the current or voltage between the hot wire and the
neutral wire of the electrical socket exhibits a series of repeated
pulse signals. The inductive coil of the arc fault protection
device detects the pulse signals and converts the pulse signals to
a voltage signal. The voltage signal is amplified by the signal
amplifier and sent to the controller. If the amplitude of the pulse
signals or the their occurring frequency exceed certain
predetermined threshold, the controller sends a control signal to
the trip circuit interrupter to cut off the connection between the
AC power and the appliance to prevent further damage caused by the
arc fault.
[0007] Leakage current protection devices have been widespreadly
used because of their superior performance. However, the leakage
protection devices may fail to provide such leakage current
protection, if they are installed improperly and/or they are
damaged due to aging. If a faulty controller can not output a
correct control signal, or a trip mechanism fails to cut off the
connection between the AC power and the appliance, the leakage
current protection device will not be able to provide the leakage
current protection, which may cause further damages or accidents.
Although most leakage current protection devices are equipped with
a manual testing button, usually, users seldom use the manual
testing button. Therefore, the leakage current protection devices
need an additional circuit to automatically detect malfunctions,
faults or the end of the life of such devices. The great relevance
would be gained if a leakage current protection device is capable
of automatically detecting a fault therein or its end of the life,
and consequently alerting a user to take an appropriate action
including repairing or replacing the leakage current detection
circuit.
[0008] Therefore, a heretofore unaddressed need exists in the art
to address the aforementioned deficiencies and inadequacies.
SUMMARY OF THE PRESENT INVENTION
[0009] In one aspect, the present invention relates to an apparatus
for testing the life of a leakage current protection device. The
leakage current protection device has a first inductive coil N1, a
second inductive coil N2, a first input, a second input, a first
output electrically coupled to the second input through the first
inductive coil N1 and the second inductive coil N2, a second
output, a third output, a trip switch SW101 having two LINE
terminals and electrically coupled to the first input and the
second input, respectively, for receiving an AC power, and two LOAD
terminals and electrically coupled to the inputs of an electrical
appliance, respectively, a power supply circuit having an input
electrically coupled to the first input, and an output electrically
coupled to the second output, a trip coil circuit having a
switching device VD1 having a gate, an anode and a cathode, an
input, an output electrically coupled to the third output, and a
leakage current detection circuit having an output electrically
coupled to the input of the trip coil circuit, and a power supply
inputp electrically coupled to the output of the power supply
circuit and the second output.
[0010] In one embodiment, the apparatus includes a trip mechanism
state generator having a first input electrically coupled to the
third output of the leakage current protection device, a second
input electrically coupled to the first input of the leakage
current protection device, a third input electrically coupled to
the second input of the leakage current protection device, a first
output and a second output. The trip mechanism state generator is
adapted for generating a trip mechanism state at the first output
and the second output, where the trip mechanism state has a first
state and a second state. When the trip mechanism state is in the
first state, there is no fault exist in the leakage current
protection device. When the trip mechanism state is in the second
state, there is at least one fault exists in the leakage current
protection device.
[0011] In one embodiment, the trip mechanism state generator has: a
first diode D1 having a cathode and an anode electrically coupled
to the second input of the trip mechanism state generator; a second
diode D2 having a cathode electrically coupled to the cathode of
the first diode D1 and the first input of the trip mechanism state
generator, and an anode electrically coupled to the third input of
the trip mechanism state generator; a third diode D3 having an
anode and a cathode electrically coupled to the second input of the
leakage current protection device and the anode of the second diode
D2; a fourth diode D4 having a cathode electrically coupled to the
anode of the first diode D1 and the first input of the leakage
current protection-device, and an anode electrically coupled to a
first output of the trip mechanism state generator; a fifth
resistor R5 having a first terminal electrically coupled to the
first output of the trip mechanism state generator, and a second
terminal electrically coupled to the second output; and a sixth
resistor R6 having a first terminal electrically coupled to the
second terminal of the fifth resistor R5 and the second output of
the trip mechanism state generator, and a second terminal
electrically coupled to the anode of the third diode D3.
[0012] The apparatus also includes a fault alarm generator having a
first input electrically coupled to the first output of the trip
mechanism state generator, a second input electrically coupled to
the second output of the trip mechanism state generator, and a
power supply input electrically coupled to the second output of the
leakage current protection device.
[0013] In one embodiment, the fault alarm circuit has a
multi-vibrator having a light emitting diode (LED) D8. The
multi-vibrator generates no vibration indicating that there is no
fault in the leakage current protection device when the fault alarm
circuit receives a negative DC voltage, while the multi-vibrator
generates vibrations and a visible alarm through the LED D8
indicating that there is at least one fault in the leakage current
protection device when the fault alarm circuit receives a positive
DC voltage. In one embodiment, the fault alarm circuit comprises an
audio alarm circuit for generating an audible alarm.
[0014] The apparatus further includes a ground fault simulation
unit having an input electrically coupled to the first input of the
leakage current protection device, and an output electrically
coupled to the first output of the leakage current protection
device.
[0015] In one embodiment, the ground fault simulation unit has: a
first resistor R1 having a first terminal and a second terminal; a
second resistor R2 having a first terminal and a second terminal; a
third resistor R3 having a first terminal and a second terminal; a
seventh diode D7 having a cathode and an anode, wherein the anode
of the seventh diode D7 is connected to the input that is
electrically coupled a hot wire of the AC power, and the cathode of
the seventh diode D7 is connected to both the first terminal of the
resistor R1 and the first terminal of the second resistor R2; a
first transistor Q1 having a first collector electrically coupled
to the second terminal of the first resistor R1, a first emitter
electrically coupled to both the second terminal of the third
resistor R3 and the output, and a first base; and a sixth zener
diode D6 having an anode electrically coupled to the base of the
first transistor Q1, and a cathode electrically coupled to both the
second terminal of the second resistor R2 and the first terminal of
the third resistor R3.
[0016] In another embodiment, the ground fault simulation unit has:
a first resistor R1 having a first terminal and a second terminal;
a second resistor R2 having a first terminal and a second terminal;
a third resistor R3 having a first terminal and a second terminal
electrically coupled to the second output2; a seventh diode D7
having an anode electrically coupled to the input of the ground
fault simulation unit, and a cathode electrically coupled to both
the first terminal of the first resistor R1 and the first terminal
of the second resistor R2; a first transistor Q1 having a first
collector electrically coupled to the second terminal of the first
resistor R1, a first emitter electrically coupled to the second
input of the leakage current protection device, and a base; and a
sixth zener diode D6 having an anode electrically coupled to the
base of the first transistor Q1, and a cathode electrically coupled
to both the second terminal of the second resistor R2 and the first
terminal of the third resistor R3.
[0017] In yet another embodiment, the ground fault simulation unit
has: a first resistor R1 having a first terminal and a second
terminal; a seventh diode D7 having an anode electrically coupled
to the input, and a cathode electrically coupled to the first
terminal of the resistor R1; and a transformer T1 having a primary
winding having a first primary terminal P1 and a second primary
terminal P2, and a secondary winding having a first secondary
terminal S1 and a second secondary terminal S2, wherein the first
primary terminal P1 is electrically coupled to the second terminal
of the first resistor R1, the second primary terminal P2 is
electrically coupled to the second input of the leakage current
protection device, the first secondary terminal S1 is electrically
coupled to the second secondary terminal S2 through the first
inductive coil N1 and the second inductive coil N2.
[0018] In an alternative embodiment, the ground fault simulation
unit has: a seventh diode D7 having a cathode and an anode
electrically coupled to the input; and a first resistor R1 having a
first terminal electrically coupled to the cathode of the seventh
diode D7, and a second terminal electrically coupled to the
output.
[0019] In yet an alternative embodiment, the ground fault
simulation unit has: a first resistor R1 having a first terminal
and second terminal; a seventh diode D7 having an anode
electrically coupled to the input, and a cathode electrically
coupled to the first terminal of the first resistor R1; and a sixth
zener diode D6 having a cathode electrically coupled to the second
terminal of the first resistor R1, and an anode electrically
coupled to the output.
[0020] In operation, the ground fault simulation unit generates a
simulated ground fault signal during every positive half-wave of
the AC power, the simulated ground fault signal is detected by the
leakage current detection circuit, the leakage current detection
circuit responsively generates a signal to turn the switching
device VD1 into its conductive state so as to allow a current to
pass therethrough, the passed current is converted into a DC
voltage in accordance with a trip mechanism state generated by the
trip mechanism state generator, the fault alarm circuit receives
and analyzes the DC voltage and indicates whether a fault exists in
the leakage current protection device. In one embodiment, the DC
voltage is detected at the first terminal and the second terminal
of the resistor R5 of the trip mechanism state generator. The DC
voltage is a negative voltage if there is no fault in the leakage
current protection device, and wherein the DC voltage is a positive
voltage if there is at least one fault in the leakage current
protection device.
[0021] In another aspect, the present invention relates to a method
for intelligently testing the life of a leakage current protection
device. The leakage current protection device has a first inductive
coil N1, a second inductive coil N2, a first input, a second input,
a first output electrically coupled to the second input through the
first inductive coil N1 and the second inductive coil N2, a second
output, a third output, a trip switch SW101 having two LINE
terminals and electrically coupled to the first input and the
second input, respectively, for receiving an AC power, and two LOAD
terminals and electrically coupled to the inputs of an electrical
appliance, respectively, a power supply circuit having an input
electrically coupled to the first input, and an output electrically
coupled to the second output, a trip coil circuit having a
switching device VD1 having a gate, an anode and a cathode, an
input, an output electrically coupled to the third output, and a
leakage current detection circuit having an output electrically
coupled to the input of the trip coil circuit, and a power supply
inputp electrically coupled to the output of the power supply
circuit and the second output.
[0022] In one embodiment, the method includes the step of providing
a testing device having a trip mechanism state generator having a
first input electrically coupled to the third output of the leakage
current protection device, a second input electrically coupled to
the first input of the leakage current protection device, a third
input electrically coupled to the second input of the leakage
current protection device, a first output and a second output,
wherein the trip mechanism state generator is adapted for
generating a trip mechanism state at the first output and the
second output, wherein the trip mechanism state has a first state
and a second state; a fault alarm generator having a first input
electrically coupled to the first output of the trip mechanism
state generator, a second input electrically coupled to the second
output of the trip mechanism state generator, and a power supply
input electrically coupled to the second output of the leakage
current protection device; and a ground fault simulation unit
having an input electrically coupled to the first input of the
leakage current protection device, and an output electrically
coupled to the first output of the leakage current protection
device.
[0023] The method further includes the steps of generating a
simulated ground fault signal during every positive half-wave of
the AC power by the ground fault simulation unit; detecting the
simulated ground fault signal at the leakage current detection
circuit; generating a signal to turn the switching device VD1 into
its conductive state so as to allow a current to pass therethrough;
generating a DC voltage in responsive to a trip mechanism state at
the trip mechanism state generator, wherein the trip mechanism
state is in a first state that there is no fault exist in the
leakage current protection device, or in a second state that there
is at least one fault exists in the leakage current protection
device; receiving the DC voltage at the fault alarm circuit; and
indicating whether at least one fault exists in the leakage current
protection device. In one embodiment, the indicating step includes
the step of producing a visible alarm and/or an audible alarm.
[0024] In yet another aspect, the present invention relates to an
apparatus for life testing. In one embodiment, the apparatus has a
leakage current protection device having a first inductive coil N1,
a second inductive coil N2, a first input, a second input, a first
output electrically coupled to the second input through the first
inductive coil N1 and the second inductive coil N2, a second
output, a third output, a trip switch SW101 having two LINE
terminals and electrically coupled to the first input and the
second input, respectively, for receiving an AC power, and two LOAD
terminals and electrically coupled to the inputs of an electrical
appliance, respectively, a power supply circuit having an input
electrically coupled to the first input, and an output electrically
coupled to the second output, a trip coil circuit having a
switching device VD1 having a gate, an anode and a cathode, an
input, an output electrically coupled to the third output, and a
leakage current detection circuit having an output electrically
coupled to the input of the trip coil circuit, and a power supply
inputp electrically coupled to the output of the power supply
circuit and the second output
[0025] Furthermore, the apparatus includes a trip mechanism state
generator having a first input electrically coupled to the third
output of the leakage current protection device, a second input
electrically coupled to the first input of the leakage current
protection device, a third input electrically coupled to the second
input of the leakage current protection device, a first output and
a second output. The trip mechanism state generator is adapted for
generating a trip mechanism state at the first output and the
second output, where the trip mechanism state has a first state and
a second state. When the trip mechanism state is in the first
state, there is no fault exist in the leakage current protection
device. When the trip mechanism state is in the second state, there
is at least one fault exists in the leakage current protection
device.
[0026] Moreover, the apparatus also includes a fault alarm
generator having a first input electrically coupled to the first
output of the trip mechanism state generator, a second input
electrically coupled to the second output of the trip mechanism
state generator, and a power supply input electrically coupled to
the second output of the leakage current protection device.
[0027] Additionally, the apparatus further includes a ground fault
simulation unit having an input electrically coupled to the first
input of the leakage current protection device, and an output
electrically coupled to the first output of the leakage current
protection device.
[0028] In operation, the ground fault simulation unit generates a
simulated ground fault signal during every positive half-wave of
the AC power, the simulated ground fault signal is detected by the
leakage current detection circuit, the leakage current detection
circuit responsively generates a signal to turn the switching
device VD1 into its conductive state so as to allow a current to
pass therethrough, the passed current is converted into a DC
voltage in accordance with a trip mechanism state generated by the
trip mechanism state generator, the fault alarm circuit receives
and analyzes the DC voltage and indicates whether a fault exists in
the leakage current protection device.
[0029] In one embodiment, the trip mechanism state generator has: a
first diode D1 having a cathode and an anode electrically coupled
to the second input of the trip mechanism state generator; a second
diode D2 having a cathode electrically coupled to the cathode of
the first diode D1 and the first input of the trip mechanism state
generator, and an anode electrically coupled to the third input of
the trip mechanism state generator; a third diode D3 having an
anode and a cathode electrically coupled to the second input of the
leakage current protection device and the anode of the second diode
D2; a fourth diode D4 having a cathode electrically coupled to the
anode of the first diode D1 and the first input of the leakage
current protection device, and an anode electrically coupled to a
first output of the trip mechanism state generator; a fifth
resistor R5 having a first terminal electrically coupled to the
first output of the trip mechanism state generator, and a second
terminal electrically coupled to the second output; and a sixth
resistor R6 having a first terminal electrically coupled to the
second terminal of the fifth resistor R5 and the second output of
the trip mechanism state generator, and a second terminal
electrically coupled to the anode of the third diode D3. In one
embodiment, the DC voltage is detected at the first terminal and
the second terminal of the resistor R5. The DC voltage is a
negative voltage if there is no fault in the leakage current
protection device, and wherein the DC voltage is a positive voltage
if there is at least one fault in the leakage current protection
device.
[0030] In one embodiment, the fault alarm circuit has a
multi-vibrator having a light emitting diode (LED) D8. The
multi-vibrator generates no vibration indicating that there is no
fault in the leakage current protection device when the fault alarm
circuit receives a negative DC voltage, while the multi-vibrator
generates vibrations and a visible alarm through the LED D8
indicating that there is at least one fault in the leakage current
protection device when the fault alarm circuit receives a positive
DC voltage. In one embodiment, the fault alarm circuit comprises an
audio alarm circuit for generating an audible alarm.
[0031] In one embodiment, the ground fault simulation unit has: a
first resistor R1 having a first terminal and a second terminal; a
second resistor R2 having a first terminal and a second terminal; a
third resistor R3 having a first terminal and a second terminal; a
seventh diode D7 having a cathode and an anode, wherein the anode
of the seventh diode D7 is connected to the input that is
electrically coupled a hot wire of the AC power, and the cathode of
the seventh diode D7 is connected to both the first terminal of the
resistor R1 and the first terminal of the second resistor R2; a
first transistor Q1 having a first collector electrically coupled
to the second terminal of the first resistor R1, a first emitter
electrically coupled to both the second terminal of the third
resistor R3 and the output, and a first base; and a sixth zener
diode D6 having an anode electrically coupled to the base of the
first transistor Q1, and a cathode electrically coupled to both the
second terminal of the second resistor R2 and the first terminal of
the third resistor R3.
[0032] In another embodiment, the ground fault simulation unit has:
a first resistor R1 having a first terminal and a second terminal;
a second resistor R2 having a first terminal and a second terminal;
a third resistor R3 having a first terminal and a second terminal
electrically coupled to the second output2; a seventh diode D7
having an anode electrically coupled to the input of the ground
fault simulation unit, and a cathode electrically coupled to both
the first terminal of the first resistor R1 and the first terminal
of the second resistor R2; a first transistor Q1 having a first
collector electrically coupled to the second terminal of the first
resistor R1, a first emitter electrically coupled to the second
input of the leakage current protection device, and a base; and a
sixth zener diode D6 having an anode electrically coupled to the
base of the first transistor Q1, and a cathode electrically coupled
to both the second terminal of the second resistor R2 and the first
terminal of the third resistor R3.
[0033] In yet another embodiment, the ground fault simulation unit
has: a first resistor R1 having a first terminal and a second
terminal; a seventh diode D7 having an anode electrically coupled
to the input, and a cathode electrically coupled to the first
terminal of the resistor R1; and a transformer T1 having a primary
winding having a first primary terminal P1 and a second primary
terminal P2, and a secondary winding having a first secondary
terminal S1 and a second secondary terminal S2, wherein the first
primary terminal P1 is electrically coupled to the second terminal
of the first resistor R1, the second primary terminal P2 is
electrically coupled to the second input of the leakage current
protection device, the first secondary terminal S1 is electrically
coupled to the second secondary terminal S2 through the first
inductive coil N1 and the second inductive coil N2.
[0034] In an alternative embodiment, the ground fault simulation
unit has: a seventh diode D7 having a cathode and an anode
electrically coupled to the input; and a first resistor R1 having a
first terminal electrically coupled to the cathode of the seventh
diode D7, and a second terminal electrically coupled to the
output.
[0035] In yet an alternative embodiment, the ground fault
simulation unit has: a first resistor R1 having a first terminal
and second terminal; a seventh diode D7 having an anode
electrically coupled to the input, and a cathode electrically
coupled to the first terminal of the first resistor R1; and a sixth
zener diode D6 having a cathode electrically coupled to the second
terminal of the first resistor R1, and an anode electrically
coupled to the output.
[0036] These and other aspects of the present invention will become
apparent from the following description of the preferred embodiment
taken in conjunction with the following drawings, although
variations and modifications therein may be affected without
departing from the spirit and scope of the novel concepts of the
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The accompanying drawings illustrate one or more embodiments
of the invention and, together with the written description, serve
to explain the principles of the invention. Wherever possible, the
same reference numbers are used throughout the drawings to refer to
the same or like elements of an embodiment, and wherein:
[0038] FIG. 1 shows a block diagram of an apparatus for
intelligently testing the life of a leakage current protection
device according to one embodiment of the present invention;
[0039] FIG. 2 shows a circuit diagram of an apparatus for
intelligently testing the life of a leakage current protection
device according to one embodiment of the present invention;
[0040] FIG. 3 shows (A) an AC power signal waveform; (B) a waveform
measured at a first end of the trip coil J, point V3 shown in FIG.
2, and (C) the waveform of a simulated ground fault current
according to embodiments of the present invention; and
[0041] FIG. 4 shows four different embodiments (A)-(D) of a ground
fault simulation unit according to embodiments of the present
invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0042] The present invention is more particularly described in the
following examples that are intended as illustrative only since
numerous modifications and variations therein will be apparent to
those skilled in the art. Various embodiments of the invention are
now described in detail. Referring to the drawings, like numbers
indicate like parts throughout the views. As used in the
description herein and throughout the claims that follow, the
meaning of "a," "an," and "the" includes plural reference unless
the context clearly dictates otherwise. Also, as used in the
description herein and throughout the claims that follow, the
meaning of "in" includes "in" and "on" unless the context clearly
dictates otherwise. Moreover, titles or subtitles may be used in
the specification for the convenience of a reader, which has no
influence on the scope of the invention. Additionally, some terms
used in this specification are more specifically defined below.
DEFINITIONS
[0043] The terms used in this specification generally have their
ordinary meanings in the art, within the context of the invention,
and in the specific context where each term is used.
[0044] Certain terms that are used to describe the invention are
discussed below, or elsewhere in the specification, to provide
additional guidance to the practitioner in describing the apparatus
and methods of the invention and how to make and use them. For
convenience, certain terms may be highlighted, for example using
italics and/or quotation marks. The use of highlighting has no
influence on the scope and meaning of a term; the scope and meaning
of a term is the same, in the same context, whether or not it is
highlighted. Whether or not a term is capitalized is not considered
definitive or limiting of the meaning of a term. As used in the
description herein and throughout the claims that follow, a
capitalized term shall have the same meaning as an uncapitalized
term, unless the context of the usage specifically indicates that a
more restrictive meaning for the capitalized term is intended. It
will be appreciated that the same thing can be said in more than
one way. Consequently, alternative language and synonyms may be
used for any one or more of the terms discussed herein, nor is any
special significance to be placed upon whether or not a term is
elaborated or discussed herein. Synonyms for certain terms are
provided. A recital of one or more synonyms does not exclude the
use of other synonyms. The use of examples anywhere in this
specification, including examples of any terms discussed herein, is
illustrative only, and in no way limits the scope and meaning of
the invention or of any exemplified term. Likewise, the invention
is not limited to various embodiments given in this specification.
Furthermore, subtitles may be used to help a reader of the
specification to read through the specification, which the usage of
subtitles, however, has no influence on the scope of the
invention.
[0045] As used herein, "around", "about" or "approximately" shall
generally mean within 20 percent, preferably within 10 percent, and
more preferably within 5 percent of a given value or range.
Numerical quantities given herein are approximate, meaning that the
term "around", "about" or "approximately" can be inferred if not
expressly stated.
[0046] As used herein, the terms "unit" and "circuit" are
interchangeable, and refer to a configuration of electrically or
electromagnetically electrically coupled components or devices.
[0047] The term "switch" or "switching device", refers to a device
for changing the course (or flow) of a circuit, i.e., a device for
making or breaking an electric circuit, or for selecting between
multiple circuits. As used herein, a switch or switching device has
two states: a conductive state and a non-conductive state. When the
switching device is in the conductive state, a current is allowed
to pass through. When the switching device is in the non-conductive
state, no current is allowed to pass through.
[0048] As used herein, short names, acronyms and/or abbreviations
"AC" refers to alternate current; "DC" refers to direct current;
"AFCI" refers to arc fault circuit interrupter; "GFCI" refers to
ground fault circuit interrupter; "LED" refers to light emitting
diode; "MCU" refers to microcontroller unit; and "SCR" refers to
silicon controlled rectifier.
EMBODIMENTS OF THE INVENTION
[0049] The description will be made as to the embodiments of the
present invention in conjunction with the accompanying drawings in
FIGS. 1-4. In accordance with the purposes of this invention, as
embodied and broadly described herein, this invention, in one
aspect, relates to apparatus for intelligently testing the life of
a leakage current protection device.
[0050] Referring to FIGS. 1-4, and particularly to FIGS. 1 and 2
first, an apparatus 300 for intelligently testing the life of a
leakage current protection device, according to embodiments of the
present invention, has a leakage current protection device 100, a
ground fault simulation unit 250 and an intelligent life testing
and alarm circuit 200.
[0051] The leakage current protection device 100 has a first input
151, a second input 153, a first output 172, a second output 174, a
third output 176. The leakage current protection device 100 further
has a power supply circuit 102 having an input 102a electrically
coupled to the first input 151, and an output 102b electrically
coupled to the second output 174. Moreover, the leakage current
protection device 100 has a trip coil circuit 103 having an input
103a, an output 103b electrically coupled to the third output 176.
Additionally, the leakage current protection device 100 has a
leakage current detection circuit 107 having an output 107b
electrically coupled to the input 103a of the trip coil circuit
103, and a power supply input 107p electrically coupled to the
output 102b of the power supply circuit 102 and the second output
174. The leakage current protection device 100 also has a trip
switch SW101, a manual testing circuit 104 and a metal oxide
varistors (MOV) MOV1. Furthermore, the leakage current protection
device 100 has a first inductive coil N1 and a second inductive
coil N2 coupled with the line phase and neutral wires of an AC
power for detecting leakage current.
[0052] The trip switch SW101 has two LINE terminals 151a and 153a
that are electrically coupled to the first input 151 and the second
input 153, through the first inductive coil N1 and the second
inductive coil N2, respectively, and two LOAD terminals 151b and
153b electrically connected to one or more electric appliances. The
first input 151 and the second input 153 are electrically connected
to an incoming AC power. When the trip switch SW101 is in a
conductive state, the AC power is connected from the LINE terminals
151a and 153a to the LOAD terminals 151b and 153b. When the SW101
is in a non-conductive state, the AC power to the LOAD terminals
151b and 153b is disconnected from the LINE terminals 151a and
153a. The LOAD terminals 151b and 153b may be also connected to an
outlet receptacle.
[0053] The two inductive coils N1 and N2 are adapted for detecting
leakage current. When a current passing through a first input 151
to the LOAD terminal 151b of the trip switch SW101 is substantially
different from a current passing through the second input 153 for
the LOAD terminal 153b, the inductive coils N1 and N2 detect the
difference and a leakage current is consequently sent to the
leakage current detection circuit 107.
[0054] When the leakage current detection circuit 107 receives the
leakage current from the inductive coils N1 and N2, and it compares
the leakage current with a predetermined threshold. If the leakage
current is greater than the predetermined threshold, a ground fault
exists, then the leakage current detection circuit 107 sends a
signal to the trip coil circuit 103 to disconnect the AC power from
the LINE terminals 151a and 153a to the LOAD terminals 151b and
153b. The leakage current detection circuit 107 is a part of
leakage current protection device 100 and known to those skilled in
the art.
[0055] The half-wave power supply circuit 102 has a fifth diode D5
having an anode and a cathode and a seventh current limiting
resistor R7 having a first and second terminals and an eighth
current limiting resistor R8 having a first and second terminals.
The anode of the fifth diode D5 is electrically connected to the
second input 153 that is connected the one of the line phase and
neutral wires of the AC power, and the cathode of the fifth diode
D5 is electrically connected to both the first terminals of the
resistor R7 and the resistor R8. The second terminal of the
resistor R7 is electrically connected to the input 107a of the
leakage current detection circuit 107. For such a configuration,
the current at the cathode of the fifth diode D5 is direct current.
The current limiting resistors are used to convert the current into
a voltage and reduce it at the output. The power supply 102 is
connected through the second terminal of the seventh resistor R7 to
the leakage current detection circuit 107. The power supply 102 is
also connected through the second terminal of the eighth resistor
R8 to a fault alarm circuit 202.
[0056] The trip coil circuit 103 includes a switching device VD1
having a gate, an anode and a cathode, a first capacitor C1 having
a first and second terminals, a twelfth resistor R12, and a trip
coil J electrically connected between the trip mechanism state
generator 201 and the anode of the switching device VD1. The
cathode of the switching device VD1 is electrically connected to
the fault alarm circuit 202. The twelfth resistor R12 is
electrically connected between the gate of the switching device VD1
and the output 107b of the leakage current detection circuit 107.
The first capacitor C1 has its first terminal connected to the
output 107b of the leakage current detection circuit 107 and its
second terminal connected to the fault alarm circuit 202, as shown
in FIG. 2. An input signal to the gate of the switching device VD1
from the output 107b of the leakage current detection circuit 107
through the twelfth resistor R12 makes the switching device VD1
either in a conductive or a non-conductive state. When the
switching device VD1 is in the conductive state, the trip coil J is
connected to the power supply and the trip coil sets the trip
switch SW101 into a non-conductive state (a trip state).
[0057] The manual testing circuit 104 has a resistor R0 and a
push-on release-off switch TEST that are connected in series. The
manual testing circuit 104 is electrically connected between the
MOV1 and the LOAD terminal 151b of the trip switch SW101 and
adapted for manually testing the leakage current protection device
100.
[0058] The trip switch SW101 maintains its state until a current
passes through the trip coil J. The trip switch SW101 responds to
the action of the trip coil J. When the leakage current detection
circuit 107 detects the leakage current, a signal from the leakage
current detection circuit is sent to the gate of the switching
device VD1, which sets the switching device VD1 to its conductive
state. The power supply 102 energizes the trip coil J to set the
trip switch SW101 in its non-conductive state so that the AC power
is disconnected from the LINE terminals 151a and 153a to the LOAD
terminals 151b and 153b, i.e. in a trip state. If the leakage
current protection device 100 does not have an automatic reset
circuit, the leakage current protection device in a trip state can
be manually reset by pressing a reset button.
[0059] As shown in FIG. 1, the apparatus 300 includes a trip
mechanism state generator 201 having a first input 201a1
electrically coupled to the third output 176 of the leakage current
protection device 100, a second input 201a2 electrically coupled to
the first input 151 of the leakage current protection device 100, a
third input 201a3 electrically coupled to the second input 153 of
the leakage current protection device 100, a first output 201b1 and
a second output 201b2. The trip mechanism state generator 201 is
adapted for generating a trip mechanism state at the first output
201b1 and the second output 201b2, where the trip mechanism state
has a first state and a second state. When the trip mechanism state
is in the first state, there is no fault exist in the leakage
current protection device 100. When the trip mechanism state is in
the second state, there is at least one fault exists in the leakage
current protection device 100.
[0060] As shown in FIG. 2, the trip mechanism state generator 201
has a first diode D1 having a cathode and an anode electrically
coupled to the second input 201a2 of the trip mechanism state
generator 201; a second diode D2 having a cathode electrically
coupled to both the cathode of the first diode D1 and the first
input 201a1 of the trip mechanism state generator 201, and an anode
electrically coupled to the third input 201a3 of the trip mechanism
state generator 201; a third diode D3 having an anode and a cathode
electrically coupled to both the second input 153 of the leakage
current protection device 100 and the anode of the second diode D2;
a fourth diode D4 having a cathode electrically coupled to both the
anode of the first diode D1 and the first input 151 of the leakage
current protection device 100, and an anode electrically coupled to
a first output 201b1 of the trip mechanism state generator 201; a
fifth resistor R5 having a first terminal electrically coupled to
the first output 201bl of the trip mechanism state generator 201,
and a second terminal electrically coupled to the second output
201b2; and a sixth resistor R6 having a first terminal electrically
coupled to the second terminal of the fifth resistor R5 and the
second output 201b2 of the trip mechanism state generator 201, and
a second terminal electrically coupled to the anode of the third
diode D3.
[0061] The trip mechanism state generator 201 generates two
distinct states: one indicating that the trip mechanism of the
leakage current protection device 100 is working properly, and the
other indicating that the trip mechanism of the leakage current
protection device 100 is out of order. The trip mechanism state
generator 201 is an asymmetric bridge rectifying circuit. The
bridge rectifying circuit provides a first current path and a
second current path. In one embodiment, the first path starts from
a first wire of an AC power (for example, through the first input
151 of the leakage current protection device 100), going through
the first diode D1, the trip coil J, the switching device VD1 of
the trip coil circuit 103, the fifth resistor R5, the sixth
resistor R6, the third diode D3 and returning to the second wire of
the AC power (for example, through the second input 153 of the
leakage current protection device 100). The second path starts from
the second wire of the AC power, going through the second diode D2,
the trip coil J, the switching device VD1 of the trip coil circuit
103, the fourth diode D4 and returning to the first wire of the AC
power. The first wire of the AC power can be one of a hot wire and
a neutral wire, whole the second wire of the AC power is chosen to
be the other of a hot wire and a neutral wire.
[0062] The apparatus 300 also includes a fault alarm generator 202
having a first input 202a1 electrically coupled to the first output
201b1 of the trip mechanism state generator 201, a second input
202a2 electrically coupled to the second output 201b2 of the trip
mechanism state generator 201, and a power supply input 202p
electrically coupled to the second output 172 of the leakage
current protection device 100, as shown in FIG. 1.
[0063] As shown in FIG. 2, the fault alarm circuit 202 comprises a
light emitting diode (LED) D8, a second transistor Q2, a third
transistor Q3, a second capacitor C2, a third capacitor C3, a ninth
resistor R9, a tenth resistor R10 and a eleventh resistor R11. The
fault alarm circuit 202 is a multi-vibrator. The input to the fault
alarm circuit 202 is the voltage between the base of the second
transistor Q2 and the emitters of the second and the third
transistors Q2 and Q3. These two terminals are connected to both
ends of the fifth resistor R5 of the trip mechanism state generator
201. When the voltage is greater than a predetermined level, a
vibration is started in the fault alarm circuit 202 and the LED D8
starts to flash, indicating at least one fault exists in the trip
mechanism of the leakage current protection device. When the
voltage is less than the predetermined level, the multi-vibrator
will not vibrate in the fault alarm circuit 202 and the LED D8
remains dark, indicating no fault exists in the trip mechanism of
the leakage current protection device. In one embodiment, the
predetermined level of the voltage can be set to zero. Therefore,
when the fault alarm circuit 202 receives a negative DC voltage,
the multi-vibrator generates no vibration indicating that there is
no fault in the leakage current protection device 100. When the
fault alarm circuit 202 receives a positive DC voltage, the
multi-vibrator generates vibrations and a visible alarm through the
LED D8 indicating that there is at least one fault in the leakage
current protection device 100. The fault alarm circuit 202 may
include an audio alarm circuit for generating an audible alarm.
[0064] In one embodiment, the DC voltage is detected at the first
terminal and the second terminal of the resistor R5 of the trip
mechanism state generator 201.
[0065] Furthermore, the apparatus 300 further includes a ground
fault simulation unit 250 having an input 250a electrically coupled
to the first input 151 of the leakage current protection device
100, and an output 250b electrically coupled to the first output
172 of the leakage current protection device 100, as shown in FIG.
1.
[0066] As shown in FIG. 2, the ground fault simulation unit 250 has
a first resistor R1 having a first terminal and a second terminal;
a second resistor R2 having a first terminal and a second terminal;
a third resistor R3 having a first terminal and a second terminal;
a seventh diode D7 having a cathode and an anode, wherein the anode
of the seventh diode D7 is connected to the input 250a that is
electrically coupled to a first wire of an AC power through the
first input 151 of the leakage current protection device 100, and
the cathode of the seventh diode D7 is connected to both the first
terminal of the resistor R1 and the first terminal of the second
resistor R2; a first transistor Q1 having a first collector
electrically coupled to the second terminal of the first resistor
R1, a first emitter electrically coupled to both the second
terminal of the third resistor R3 and the output terminal 250b, and
a first base; and a sixth zener diode D6 having an anode
electrically coupled to the base of the first transistor Q1, and a
cathode electrically coupled to both the second terminal of the
second resistor R2 and the first terminal of the third resistor
R3.
[0067] This output terminal 250b of the ground fault simulation
unit 250 is connected to a second wire of the AC power after the
second wire (the first input terminal 153 of the leakage current
protection device 100, for example) passes the first and the second
inductive coils N1 and N2. During a positive half-wave of the AC
power, the first transistor Q1 is in a non-conductive state at
first. As the input voltage increases, the first transistor Q1
remains in its non-conductive state until the input voltage is
greater than the voltage difference between the collector terminal
and the emitter terminal of the first transistor Q1. At this point
the first transistor Q1 becomes conductive. After the input voltage
reaches its peak and the first transistor Q1 remains conductive
until the input voltage is less than the voltage difference between
the collector terminal and the emitter terminal of the first
transistor Q1. At this point the first transistor Q1 becomes
non-conductive. The first transistor Q1 remains non-conductive
until the input voltage is greater than the voltage difference
between the collector terminal and the emitter terminal of the
first transistor Q1 during the next positive half-wave of the AC
power. A square wave signal is formed at the output of the ground
fault simulation unit 250 as a simulated ground fault signal.
[0068] Referring now to FIG. 3, three signal waveforms are
presented according to one embodiment of the present invention.
FIG. 3A is a signal wave form of the AC power input shown in full
cycle measured at the input of the ground fault simulation unit 250
marked as V.sub.1. FIG. 3B shows the signal wave form measured at
an output of an asymmetric bridge rectifier circuit marked as
V.sub.3. FIG. 3C is the square wave signal measured at the output
of the ground fault simulation unit 250. The shape of the square
wave can be adjusted by varying the parameter of the ground fault
simulation unit 250.
[0069] FIG. 4 also shows alternative embodiments of the ground
fault simulation unit 250. As shown in FIG. 3A, the ground fault
simulation unit 250 has a first resistor R1 having a first terminal
and a second terminal; a second resistor R2 having a first terminal
and a second terminal; a third resistor R3 having a first terminal
and a second terminal electrically coupled to the second output
250b2; a seventh diode D7 having an anode electrically coupled to
the input 250a of the ground fault simulation unit 250, and a
cathode electrically coupled to both the first terminal of the
first resistor R1 and the first terminal of the second resistor R2;
a first transistor Q1 having a first collector electrically coupled
to the second terminal of the first resistor R1, a first emitter
electrically coupled to the second input 153 of the leakage current
protection device 100, and a base; and a sixth zener diode D6
having an anode electrically coupled to the base of the first
transistor Q1, and a cathode electrically coupled to both the
second terminal of the second resistor R2 and the first terminal of
the third resistor R3. The input 205a of the ground fault
simulation unit 250 is electrically connected to a first wire of
the AC power, while the output 250b of the ground fault simulation
unit 250 is electrically connected to a second wire of the AC
passed the first inductive coil N1 and the second inductive coil
N2.
[0070] As shown in FIG. 4B, the ground fault simulation unit 250
has: a first resistor R1 having a first terminal and a second
terminal; a seventh diode D7 having an anode electrically coupled
to the input 250a, and a cathode electrically coupled to the first
terminal of the resistor R1; and a transformer T1 having a primary
winding having a first primary terminal P1 and a second primary
terminal P2, and a secondary winding having a first secondary
terminal S1 and a second secondary terminal S2, wherein the first
primary terminal P1 is electrically coupled to the second terminal
of the first resistor R1, the second primary terminal P2 is
electrically coupled to the second input 153 of the leakage current
protection device 100, the first secondary terminal S1 is
electrically coupled to the second secondary terminal S2 through
the first inductive coil N1 and the second inductive coil N2.
[0071] As shown in FIG. 4C, the ground fault simulation unit 250
has a seventh diode D7 having a cathode and an anode electrically
coupled to the input 250a; and a first resistor R1 having a first
terminal electrically coupled to the cathode of the seventh diode
D7, and a second terminal electrically coupled to the output 250b.
The input 205a of the ground fault simulation unit 250 is
electrically connected to a first wire of the AC power, while the
output 250b of the ground fault simulation unit 250 is electrically
connected to a second wire of the AC passed the first inductive
coil N1 and the second inductive coil N2.
[0072] As shown in FIG. 4D, the ground fault simulation unit 250
has a first resistor R1 having a first terminal and second
terminal; a seventh diode D7 having an anode electrically coupled
to the input 250a, and a cathode electrically coupled to the first
terminal of the first resistor R1; and a sixth zener diode D6
having a cathode electrically coupled to the second terminal of the
first resistor R1, and an anode electrically coupled to the output
250b. The input 205a of the ground fault simulation unit 250 is
electrically connected to a first wire of the AC power, while the
output 250b of the ground fault simulation unit 250 is electrically
connected to a second wire of the AC passed the first inductive
coil N1 and the second inductive coil N2.
[0073] In operation, the ground fault simulation unit 250 generates
a simulated ground fault signal during every positive half-wave of
the AC power, the simulated ground fault signal is detected by the
leakage current detection circuit 107, the leakage current
detection circuit 107 responsively generates a signal to turn the
switching device VD1 into its conductive state so as to allow a
current to pass therethrough, the passed current is converted into
a DC voltage in accordance with a trip mechanism state generated by
the trip mechanism state generator 201, the fault alarm circuit 202
receives and analyzes the DC voltage and indicates whether a fault
exists in the leakage current protection device 100.
[0074] Specifically, referring to FIG. 2, the ground fault
simulation unit 250 generates a simulated ground fault during every
positive half-wave of an AC power. The current after the seventh
diode D7 is connected to a voltage divider having the second
resistor R2 and the third resistor R3 to the second wire of the AC
power. The ratio of the voltage divider is determined by the values
of these two resistors R2 and R3. During the positive half-wave of
the AC power, the voltage across R2 increases until the voltage
exceeds the relative consistent voltage maintained at the sixth
zener diode D6 and the sixth zener diode D6 becomes conductive.
Then the first transistor Q1 becomes conductive as a result of the
sixth zener diode D6 becoming conductive. After the AC power
reaches its peak, the input voltage of the AC power starts to
decrease. The voltage at the cathode of the seventh diode D7
reaches a point where the sixth zener diode D6 becomes
non-conductive. The first transistor Q1 becomes non-conductive as a
result, thus forming the square wave simulated ground fault signal
as shown in FIG. 2C. This process repeats every positive half-wave.
An approximated square wave or other non-square wave signals can
also be used for simulating ground faults.
[0075] The simulated ground fault signal is detected by two
inductive coils N1 and N2 and sent to a leakage current detection
circuit 107 for processing. The output of the leakage current
detection circuit 107 is fed to a trip coil circuit 103. The trip
coil circuit 103 comprises a twelfth resistor R12, a silicon
controlled rectifier VD1, a coil J for the trip mechanism. The
simulated ground fault signal enables the leakage current detection
circuit 107 to output a signal to turn the SCR VD1 into conductive
state. During this time, a trip mechanism state generator 201
generates a state related to the status of the trip mechanism. The
trip mechanism state generator 201 comprises a first diode D1, a
second diode D2, a third diode D3, a fourth diode D4, a fifth
resistor R5 and a sixth resistor R6. These components form an
asymmetric rectifying bridge providing current through the trip
coil circuit 103.
[0076] During positive half-wave of the AC power, a first path of
current is formed from a first wire of the AC power to the second
wire of the AC power through the first diode D1, the trip coil J,
the VD1, the fifth resistor R5, the sixth resistor R6 and the third
diode D3. The values of the resistors R5 and R6 are selected so
that the current passing through the first path of current is small
enough not to trip the trip mechanism. During negative half-wave of
the AC power, a second path of current is formed from the second
wire of the AC power to the first wire of the AC power through the
second diode D2, the trip coil J, the VD1, and the fourth diode D4.
When the inductive coils N1 and N2, an IC inside the leakage
current detection circuit, the SCR VD1 are working properly, the
current through the first path generates a negative voltage across
the fifth resistor R5, i.e. the voltage at the point marked as O2
is lower than the voltage at the point marked as O1. This negative
voltage indicates the proper working order of the leakage current
protection device. Otherwise, if the leakage current detection
circuit 107 fails to detect the simulated ground fault, if the trip
coil J is broken so the current could not pass through the first
path, or if the VD1 fails to respond to the signal from the leakage
current detection circuit 107, a current can not pass through the
first path and the negative voltage can not be established across
the fifth resistor R5. Therefore, the negative voltage across the
fifth resistor R5, marked as O1 and O2, reflects the status of the
leakage current protection device.
[0077] The both terminals of the fifth resistor R5, marked as O1
and O2, are connected to two input terminals of a fault alarm
circuit 202. The fault alarm circuit 202 comprises a second
transistor Q2, a third transistor Q3, a light emitting diode (LED)
D8, a second capacitor C2, a third capacitor C3, a ninth resistor
R9, a tenth resistor R10 and a eleventh resistor R11. The fault
alarm circuit 202 is a multi-vibrator. When the voltage between the
two input terminals (the voltage across the fifth resistor R5) is
negative, the second transistor Q2 is in non-conductive state and
the LED D8 is not lit. If the voltage between the two input
terminals is not negative, the multi-vibrator vibrates and the LED
D8 flashes. The frequency of the LED D8 flashing depends on the
parameters of the components used in the multi-vibrator. The
flashing frequency can be chosen from any numbers of flashes per
second as long as the flashing can be identified by human eyes. In
one embodiment, the flashing rate is one flash per second. The
flashing rate can be lower than one flash per second, and also can
be higher that one flash per second. Optionally, additional audio
alarm circuit can be added to the fault alarm circuit 202.
[0078] Another aspect of the present invention provides a method of
intelligently testing the life of a leakage current protection
device having a leakage current detection circuit and a trip
mechanism. In one embodiment, the method comprises the steps of:
[0079] detecting fault in leakage current protection device with a
fault detector; and [0080] alerting user of the leakage current
protection device with a life testing detection unit having an
fault alarm circuit when at least one fault is detected in the
leakage current protection device.
[0081] The step of detecting fault in leakage current protection
device with a fault detector comprising the step of detecting fault
in a leakage current detection circuit of the leakage current
protection device with the fault detector having (i) a trip
mechanism state generator, (ii) a ground fault simulation unit, and
(iii) a fault alarm circuit having a multivibrator.
[0082] The step of alerting user of the leakage current protection
device when at least one fault is detected in the leakage current
protection device comprises the step of alerting user of the
leakage current protection device by producing a visible visual
alarm.
[0083] The step of detecting fault in leakage current protection
device with the fault detector comprising the steps of: [0084]
producing a simulated ground fault by the ground fault simulation
unit during positive half-wave of an AC power; [0085] generating a
trip mechanism state by the trip mechanism state generator; [0086]
detecting the trip mechanism state; and [0087] determining whether
at least one fault exists in the trip mechanism of the leakage
current protection device.
[0088] If no fault exists in the leakage current detection circuit
of the leakage current detection device, the trip mechanism state
disables the vibration of the multivibrator of the fault alarm
circuit. If at least one fault exists in the leakage current
detection circuit of the leakage current protection device, the
trip mechanism state enables the vibration of the multivibrator of
the fault alarm circuit.
[0089] In another embodiment, the method for intelligently testing
the life of a leakage current protection device includes the steps
of providing a life testing device as disclosed above; generating a
simulated ground fault signal during every positive half-wave of
the AC power by the ground fault simulation unit; detecting the
simulated ground fault signal at the leakage current detection
circuit; generating a signal to turn the switching device VD1 into
its conductive state so as to allow a current to pass therethrough;
generating a DC voltage in responsive to a trip mechanism state at
the trip mechanism state generator, wherein the trip mechanism
state is in a first state that there is no fault exist in the
leakage current protection device, or in a second state that there
is at least one fault exists in the leakage current protection
device; receiving the DC voltage at the fault alarm circuit; and
indicating whether at least one fault exists in the leakage current
protection device. In one embodiment, the indicating step includes
the step of producing a visible alarm and/or an audible alarm.
[0090] The foregoing description of the exemplary embodiments of
the invention has been presented only for the purposes of
illustration and description and is not intended to be exhaustive
or to limit the invention to the precise forms disclosed. Many
modifications and variations are possible in light of the above
teaching.
[0091] The embodiments were chosen and described in order to
explain the principles of the invention and their practical
application so as to enable others skilled in the art to utilize
the invention and various embodiments and with various
modifications as are suited to the particular use contemplated.
Alternative embodiments will become apparent to those skilled in
the art to which the present invention pertains without departing
from its spirit and scope. Accordingly, the scope of the present
invention is defined by the appended claims rather than the
foregoing description and the exemplary embodiments described
therein.
* * * * *