U.S. patent application number 11/395336 was filed with the patent office on 2007-10-04 for grounding fault circuit interrupter.
This patent application is currently assigned to Suzhou Songbao Electric Co., Ltd.. Invention is credited to Songling Lin, Kuiyang Zhang.
Application Number | 20070230072 11/395336 |
Document ID | / |
Family ID | 38481814 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070230072 |
Kind Code |
A1 |
Zhang; Kuiyang ; et
al. |
October 4, 2007 |
GROUNDING FAULT CIRCUIT INTERRUPTER
Abstract
A grounding fault circuit interrupter (GFCI), including a
housing, a trip means, a pair of static contact pieces fixed on the
housing, a pair of load contact pieces fixed on the housing, a pair
of slide frames, a pair of movable contact pieces fixed on the
slide frames respectively, which is resiliently movable, said trip
means including a trip coil, a plunger provided in the trip coil, a
trip spring abutted against the plunger, a balance frame, a latch,
a reset pull rod, wherein said plunger is provided with an annular
groove, the plunger movably connected to the latch through the
annular groove, wherein the latch has an arc-shaped opening thereon
and is movably provided on the balance frame, said balance frame
having two wedge sides, the wedge sides in contact with the slide
frames; wherein when the reset pull rod is connected with the
latch, the static contact pieces are in contact with the movable
contact pieces. The grounding fault circuit interrupter has a
reverse wiring protection function, the receptacle inlet openings
in the face portion of which will not be energized when it's
reverse wired.
Inventors: |
Zhang; Kuiyang; (Wuijiang,
CN) ; Lin; Songling; (Wuijiang, CN) |
Correspondence
Address: |
VENABLE LLP
P.O. BOX 34385
WASHINGTON
DC
20043-9998
US
|
Assignee: |
Suzhou Songbao Electric Co.,
Ltd.
Wujiang
CN
215200
|
Family ID: |
38481814 |
Appl. No.: |
11/395336 |
Filed: |
April 3, 2006 |
Current U.S.
Class: |
361/42 |
Current CPC
Class: |
H01H 83/14 20130101;
H01H 73/20 20130101 |
Class at
Publication: |
361/042 |
International
Class: |
H02H 9/08 20060101
H02H009/08 |
Claims
1. A grounding fault circuit interrupter, including a housing, a
trip means, and a control circuit, characterized in that it further
comprises a pair of static contact pieces fixed on the housing; a
pair of load contact pieces fixed on the housing; a pair of slide
frames; a pair of movable contact pieces fixed on the slide frames
respectively, which are resiliently movable and each has one end
connected to conductive pieces through conductive strips, the
conductive pieces welded on the circuit board respectively and
passing through a sensing transformer and a neutral transformer,
said pair of slide frames resiliently and movably mounted on a coil
bracket; wherein when the static contact pieces are in contact the
movable contact pieces, the static contact pieces are electrically
connected to the load contact pieces; and wherein when the static
contact pieces are separated from the movable contact pieces, the
static contact pieces are electrically disconnected from the load
contact pieces.
2. The grounding fault circuit interrupter of claim 1, wherein the
trip means comprises a trip coil, a plunger provided in the trip
coil, a trip spring abutted against the plunger, a balance frame, a
latch, a reset pull rod slidably provided in the balance frame,
said plunger having an annular groove through which the plunger is
able to slidably connect with the latch, said latch having an
arc-shaped opening and slidably provided on the balance frame, said
balance frame having two wedge sides, the wedge sides in contact
with the slide frames; wherein when the reset pull rod is connected
with the latch, the static contact pieces are in contact with the
movable contact pieces; when the reset pull rod is separated from
the latch, the static contact pieces are withdrawn contact with the
movable contact pieces.
3. The grounding fault circuit interrupter of claim 2, wherein the
reset pull rod has a lock groove, when the reset pull rod connects
with the latch, the latch is lodged in the lock groove.
4. A grounding fault circuit interrupter, including a housing, a
trip means, a pair of static contact pieces fixed on the housing, a
pair of load contact pieces fixed on the housing, characterized in
that the grounding fault circuit interrupter further comprises a
pair of slide frames; a pair of movable contact pieces fixed on the
slide frames respectively, which is resiliently movable; said trip
means including a trip coil, a plunger provided in the trip coil, a
trip spring abutted against the plunger, a balance frame, a latch,
a reset pull rod, said plunger provided with an annular groove
through which the plunger is movably connected to the latch,
wherein the latch has an arc-shaped opening and is movably provided
on the balance frame, said balance frame having two wedge sides,
the wedge sides in contact with the slide frames; wherein when the
reset pull rod is connected with the latch, the static contact
pieces are in contact with the movable contact pieces; and wherein
when the reset pull rod is separated from the latch, the static
contact pieces are withdrawn contact with the movable contact
pieces.
5. The grounding fault circuit interrupter of claim 4, wherein the
reset pull rod has a lock groove, and when the reset pull rod
connects with the latch, the latch is lodged in the lock
groove.
6. The grounding fault circuit interrupter of claim 4, wherein
respective one ends of each said movable contact pieces are
connected with conductive strips, and the conductive strips are
connected with conductive pieces, and the conductive pieces are
welded on the circuit board respectively, and the pair of slide
frames are resiliently movable respective to the housing, wherein
when the static contact pieces are in contact with the movable
contact pieces, the static contact pieces are electrically
connected with the load contact pieces; and wherein when the static
contact pieces are separated from the movable contact pieces, the
static contact pieces are electrically disconnected from the load
contact pieces.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a grounding fault protection
device, especially a grounding fault circuit interrupter receptacle
with reverse wiring protection, the receptacle inlet openings in
the face portion of which are not energized when it's reverse
wired.
BACKGROUND OF THE INVENTION
[0002] Grounding fault circuit interrupter (GFCI) is widely used
with its effective application in preventing electric shock and
fire caused by grounding fault. A load can be connected to the
grounding fault circuit interrupter through receptacle inlet
openings in the face portion, and it also can be connected through
load binding screws. Therefore, users may miswire the line side
wiring to the load side when in installation or in use. In this
case, if a grounding fault circuit interrupter does not have the
function of reverse wiring protection, it is just like a common
receptacle without earth leakage protection, which may affect the
safety of users. Traditional GFCIs usually have certain limitations
in configuration, which may affect the performance of product or
increase the cost of product. For example, in the Chinese utility
model with patent number ZL.03243045., the GFCI adopts an
electromagnetic tripper, however it is complex in configuration and
high in cost. Moreover, it utilizes permanent magnets in tripper so
it may be greatly affected in the aspect of anti-interference. And
in the US patent with patent number U.S. Pat. No. 6,813,126,
although the GFCI has a relatively simple configuration, however
the latching fingers on the both sides of the reset switch have
quite a high requirement for manufacturing, and they may fail to
engage and even fail to reset if there's a little deviation in
their positions. Or they may disengage when vibration exists. In
addition, when the receptacle inlet openings of the face portion
are not energized, it is hard for the two movable contact points on
the movable contact pieces which has one end fixed and the other
end resiliently movable to contact the static contact points on the
static contact pieces at the same time, thus may result in strong
electric arc during the instances of on/off, shortening the
life-span of the product or it may result in loose contact after
reset, affecting the performance of the product, or even causing
danger.
BRIEF SUMMERY OF THE INVENTION
[0003] The object of the invention is to provide a grounding fault
circuit interrupter with reverse wiring protection, the receptacle
inlet openings in the face portion of which will not be energized
when it's reverse wired.
[0004] In one technical solution of the present invention, it is
provided with a grounding fault circuit interrupter, including a
housing, a trip means, and a control circuit, and it further
comprises a pair of static contact pieces fixed on the housing; a
pair of load contact pieces fixed on the housing; a pair of slide
frames; a pair of movable contact pieces fixed on the slide frames
respectively, which are resiliently movable and each has one end
connected to conductive pieces through conductive strips, the
conductive pieces welded on the circuit board respectively and
passing through a sensing transformer and a neutral transformer.
The pair of slide frames is resiliently and movably provided on a
coil bracket. When the static contact pieces are in contact the
movable contact pieces, the static contact pieces are electrically
connected to the load contact pieces; and when the static contact
pieces are separated from the movable contact pieces, the static
contact pieces are electrically disconnected from the load contact
pieces.
[0005] In another technical solution of the present invention, it
is provided with a grounding fault circuit interrupter, including a
housing, a trip means, a pair of static contact pieces fixed on the
housing, a pair of load contact pieces fixed on the housing, and
the grounding fault circuit interrupter further comprises a pair of
slide frames; a pair of movable contact pieces fixed on the slide
frames respectively, which is resiliently movable. The trip means
including a trip coil, a plunger provided in the trip coil, a trip
spring abutted against the plunger, a balance frame, a latch, a
reset pull rod. The plunger is provided with an annular groove,
through which the plunger is movably connected to the latch. The
latch has an arc-shaped opening and is movably provided on the
balance frame. The balance frame has two wedge sides, the wedge
sides in contact with the slide frames. When the reset pull rod is
connected with the latch, the static contact pieces are in contact
with the movable contact pieces; and when the reset pull rod is
separated from the latch, the static contact pieces are withdrawn
contact with the movable contact pieces.
[0006] The grounding fault circuit interrupter according to the
invention has a reverse wiring protection and receptacle inlet
openings of a face portion will not be energized when the grounding
fault circuit interrupter is reverse wired. And also it is
sensitive, convenient to assemble, low in cost and high in
anti-interference ability.
[0007] The bottom side of the reset pull rod is configured to be
flat and bigger than the arc-shaped opening in the latch of the
trip means; when the grounding fault circuit interrupter is power
off, the reset pull rod cannot go through the latch so as to reset
the interrupter; the invention further utilizes a reset control
circuit, when the grounding fault circuit interrupter is power on,
press the reset switch so that when the bottom side of the reset
pull rod connected to the reset switch is about to reach the latch,
a spring provided at one side of the reset switch switches on the
reset control circuit, produces a man-made trigger signal and gate
a silicon controlled rectifier (SCR) into conduction to energize
the trip coil. The trip coil is then energized and produces an
electromagnetic force that acts on the plunger, making the plunger
overcome the elasticity of spring and move together with the latch
connected on it, which further enables the bottom side of the reset
pull rod to go through the latch. Therefore when the arc-shaped
opening on the latch is lodged in the lock groove of reset pull
rod, the reset pull rod will move together with the latch under the
resilience of the reset spring. And the latch further makes the
balance frame to move together with it in the same direction, so
the wedge sides of the balance frame will push the slide frames,
the slide frames being arranged on both sides of the balance frame
and provided with movable contact pieces, make them overcome the
elasticity of the spring and move toward a direction that makes
them get closer, realizing the reset of the GFCI.
[0008] When the static contact pieces are separated from the load
contact pieces, they switches on the circuit through their own
contact points, thus the receptacle inlet openings in the face
portion will not be energized when it's reverse wired.
[0009] When the grounding fault circuit interrupter according to
the invention is power on, if its load side has earth leakage fault
or a wrong man-made test current is added, the control circuit will
trigger and gate the controlled silicon rectifier (SCR) into
conduction, so that the trip coil connected to the SCR at one end
will be switched on and apply an electromagnetic force on the
plunger, thereby interrupt the circuit promptly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The present invention will be further described below in
conjunction with the drawings and the embodiments:
[0011] FIG. 1 is a prospective view of a GFCI according to an
embodiment of the present invention;
[0012] FIG. 2 is a cross-sectional view, in longitudinal section,
of the GFCI in FIG. 1 showing the relative positions of the
assembly in the tripped condition;
[0013] FIG. 3 is a partly top plan view of the GFCI in FIG. 1 with
the face portion removed;
[0014] FIG. 4 is a perspective view of the GFCI in FIG. 1 with the
face portion removed, showing the internal configuration
thereof;
[0015] FIG. 5 is a partly exploded, perspective view of the GFCI in
FIG. 1;
[0016] FIG. 6 is an exploded, perspective view of the GFCI in FIG.
1;
[0017] FIG. 7 is an exploded view of the electromagnetic tripper of
the GFCI in FIG. 1;
[0018] FIG. 8 is a cross-sectional view of the GFCI in FIG. 1 in
the tripped status;
[0019] FIG. 9 is a partly prospective view of the GFCI in FIG. 1 in
the tripped status;
[0020] FIG. 10 is a cross-sectional view of the GFCI in FIG. 1 in
the closed status;
[0021] FIG. 11 is a partly prospective view of the GFCI in FIG. 1
in the closed status;
[0022] FIG. 12 is a schematic diagram of a circuit of the GFCI
according to an embodiment of the present invention;
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] Referring to the drawings, a grounding fault circuit
interrupter, including a housing (consisting of a face portion 30,
a middle body 20 and a base 10), a trip means, and a control
circuit. It further comprises a pair of static contact pieces 15,
16 fixed on the base 10; a pair of load contact pieces 17, 18 fixed
on the base 10; a pair of slide frames 13, 14; a pair of movable
contact pieces 22, 23 fixed on the slide frames 13, 14
respectively, which are resiliently movable and each has one end
connected to conductive pieces 26, 27 through conductive strips 24,
25. The conductive pieces 26, 27 are welded on the circuit board 90
respectively and going through a sensing transformer 83 and a
neutral transformer 81. The pair of slide frames 13, 14 are
resiliently and movably provided on a coil bracket 71. When the
static contact pieces 15, 16 contact the movable contact pieces 22,
23, the static contact pieces 15, 16 are electrically connected to
the load contact pieces 17, 18, and when the static contact pieces
15, 16 are separated from the movable contact pieces 22, 23, the
static contact pieces 15, 16 are electrically disconnected from the
load contact pieces 17, 18.
[0024] The trip means comprises a trip coil 72, a plunger 74
provided in the trip coil 72, a trip spring 73 abutted against the
plunger 74, a balance frame 76, a latch 75, a reset pull rod 61
slidably provided in the balance frame 76, the plunger 74 having an
annular groove 35 through which the plunger 74 is slidably
connected to the latch 75, the latch 75 having an arc-shaped
opening 12 and slidably provided on the balance frame 76, the
balance frame 76 having two wedge sides 28, 29, the wedge sides 28,
29 in contact with the slide frames 13, 14. When the reset pull rod
61 is connected with the latch 75, the static contact pieces 15, 16
are in contact with the movable contact pieces 22, 23. When the
reset pull rod 61 is separated from the latch 75, the static
contact pieces 15, 16 are withdrawn contact with the movable
contact pieces 22, 23. The reset pull rod 61 has a lock groove 11,
and when the reset pull rod 61 connects with the latch 75, the
latch 75 is lodged in the lock groove 11.
[0025] FIG. 1 shows a view of the exterior of a GFCI according to
an embodiment of the present invention, wherein 40 represents a
mounting piece, 31 represents load entry ports, 32 represents
ground-prong-receiving openings, 60 represents a reset switch, 50
represents a test switch, 30 represents a face portion, 42
represents grounding screw, 110 represents line binding screw, 111
represents load binding screw, and 113 represents indicator cover.
A load can be connected to the grounding fault circuit interrupter
through receptacle inlet openings in the face portion, and it also
can be connected through load binding screws.
[0026] The GFCI illustrated in FIG. 1 may be rated, for example, at
15 A. The present invention also provides other types of GFCI, at
various amperage ratings, and these GFCI receptacles all have two
configurations, one without an indicator and the other with an
indicator. Both configurations operate under the same principle.
Therefore, the description below, while specifically for the rated
15 A GFCI with an indicator, the description also applies to the
other types of GFCIs.
[0027] Referring to FIG. 2 and FIG. 3, the assembled relation of
the GFCI receptacle is shown in the trip condition. All of the
subassemblies and component parts are fixed mainly to the housing
(consisting of the face portion 30, the middle body 20 and the base
10) of the GFCI. A trip means is provided in the GFCI according to
the present invention. The trip means includes a shield cover 70,
one end of which is abutted against one raised side of the base 10
and the other end of which is abutted against an end portion of the
coil bracket 71, the coil bracket 71 being mounted on a circuit
board 90 by two binding pins; a trip spring 73, one end of which is
abutted against an end portion of the coil bracket 71, and the
other end of which is abutted against one end of the plunger 74,
the other end of the plunger 74 being slidably connected to the
latch 75 through an annular groove 35 set on the plunger 74; and an
arc-shaped opening, which is provided on the other end of the latch
75 and slidably arranged in a corresponding groove of the balance
frame 76; wherein the bottom side of the reset pull rod 61 is
configured to be flat and bigger than the arc-shaped opening 12 in
the latch 75; when the GFCI is power off, the reset pull rod 61
cannot go through the arc-shaped opening 12 in the latch 75, which
functions as reverse wiring protection; and when the GFCI is power
on, press the reset switch so as to produce a man-made trigger
signal which energizes the trip coil 72 and produces an instant
force acting on the plunger 74, making the plunger 74 overcome the
resilience of the trip spring 73 and move in a direction departing
the balance frame 76. Thus the bottom side of the reset pull rod 61
is able to pass through the arc-shaped opening 12 of the latch 75
and lodge the arc-shaped opening 12 in the lock groove 11 of reset
pull rod 61. And the resilience of the reset spring 62 makes the
latch 75 to move together with the balance frame 76, thereby reset
the GFCI. In this case, if a test switch 50 is pressed, a test
piece 52 will overcome the resilience of test spring 51 and get in
contact with the test resistor 53 so as to switch on the test
circuit. Thus a man-made fault current added to the GFCI realizes
the tripping of the trip means. Then the test piece 52 will prop up
the test switch 50 with its resilience, making the top surface of
the test switch 50 substantially level with the surface of the face
portion 30. A sensing bracket 80 is fixed on the circuit board 90
through four binding pins. A sensing transformer 83 and a neutral
transformer 81 are mounted on the sensing bracket 80 and between
the sensing transformer 83 and the neutral transformer 81 there is
an isolation layer 82. The sensing transformer 83 may be composed,
for example, of high original magneto-conductivity magnetic alloy
flakes and enamel-insulated wire. The neutral transformer 81 may,
for example, be composed of ferrite (high .mu. value, large
temperature modulus) and enamel-insulated wire. In order to realize
that the receptacle inlet openings in the face portion 30 are not
energized when it's reverse wired, the static contact pieces 15, 16
are withdrawn contact with the load contact pieces 17, 18,
respectively, thus they are not electrically connected with each
other and they are only able to switch on the circuit by a contact
between static contact points 101 thereon and movable contact
points 701 on the movable contact pieces 22, 23. The electricity
from the power supply reaches the conductive strips 24, 25 through
conductive pieces 26, 27 and further reaches movable contact pieces
22, 23. Respective one ends of each conductive piece 26, 27 pass
through the sensing bracket 80, the sensing transformer 83, the
isolation layer 82 and the neutral transformer 81 and are welded on
the circuit board 90, respectively. The other ends of each
conductive pieces 26, 27 are welded on the conductive pieces 26, 27
respectively. Movable contact pieces 22, 23 are arranged on the
slide frames 13, 14 respectively. A pair of springs 78 is arranged
on the coil bracket 71, each with one end abutted against the slide
frames 13, 14. The slide frames 13, 14 together with the movable
contact pieces 22, 23 with movable contact points 701 attached
thereon are kept in a trip position under the resilience of the
springs 78.
[0028] Referring to FIG. 4 and FIG. 5, a pair of static contact
pieces 15, 16 with static contact points 101 thereon are fixed on
the middle body 20. The mounting piece 40, which has a grounding
wire holder 41 and a threaded opening to receive a grounding screw
42 for connection to an external ground wire, is impacted by the
face portion 30. A resilient member is mounted below the reset
switch 60 for supporting the reset switch 60, which can be a pair
of resilient metal pieces or a spring. In this embodiment, the
resilient member is a reset spring 62 as showed in the figures. In
the situation that the reset spring 62 resiliently contacts with a
pair of lead wires 64 of the reset control circuit, the reset
control circuit is switched on such that a man-made instant current
is added to the trip coil thereby reset the GFCI.
[0029] FIG. 6 is an exploded, perspective view of the GFCI. From
this figure we can see that the GFCI according to the invention
mainly comprises a base 10, a middle body 20, a face portion 30, a
mounting piece 40 with grounding wire holders 41 and a grounding
screw 42, a pair of movable contact pieces 22, 23 with movable
contact points 701, a pair of static contact pieces 15, 16 with
static contact points 101, a trip means, a test means and a control
circuit. 19, 21 are source ends. 103 is a wire-binding board. 110
is a line binding screw. 111 is a load screw. 90 is a circuit
board. All the subassemblies and components are assembled as showed
in the figure and are impacted by four screws 115. A reset switch
opening 33 in the face portion and the reset switch 60 are matched
with each other so that the reset switch 60 is circumferentially
positioned. And also, a test switch opening 34 and a test switch 50
are matched with each other so that the test switch 50 is
positioned too. An indicating rod 114 coated with definite sign is
arranged on the slide frame 14 for indicating reset. When the GFCI
resets, the indicating rod 114 is kept in a reset position by the
slide frame 14, thereby indicates reset.
[0030] FIG. 7 is an exploded view of the trip means of the GFCI.
The trip means includes: a shield cover 70, a coil bracket 71, a
trip coil 72, a trip spring 73, a plunger 74, a latch 75, a balance
frame 76, a pair of slide frames 13, 14, a spring 78, a pin 79, a
pair of movable contact pieces 22, 23 provided on the slide frames,
a pair of movable contact points 701 riveted on the movable contact
pieces. The movable contact points 701 are kept in a trip status by
the resilience of the spring 78. A shield cover 70 is used to
enhance the anti-interference of the product. The assembled
position relation of the electromagnetic tripper is further shown
in FIG. 7.
[0031] FIG. 8 is a cross-sectional view of the GFCI in the tripped
status, and FIG. 10 is a cross-sectional view of the GFCI in the
closed status. FIG. 9 is a partly prospective view of the GFCI in
the tripped status, and FIG. 11 is a partly prospective view of the
GFCI in the closed status. When the trip coil 72 is energized, it
produces an electromagnetic force, which acts on the plunger 74 and
drives the plunger 74 back and forth together with the latch 75
connected on it. When the reset switch 60 is pressed and the reset
pull rod 61 is about to reach the latch 75, a small spring 63 will
be electrically connected to the two lead wires 64 which control
the on/off of reset control circuit, switch on the reset control
circuit and further add a man-made instant current to the trip coil
72. The trip coil 72 then produces an instant electromagnetic force
which acts on the plunger 74, causing the plunger 74 to bring away
the latch 75 so that a bottom side of the reset pull rod 61 is able
to pass through the latch 75. Under the resilience of the trip
spring 73, an arc-shaped opening in the latch 75 will be lodged
tightly in the lock groove 11 of the reset pull rod 61 and the
resilience of the reset spring 62 will further drive the latch 75
to move upward together with the balance frame 76. As the balance
frame 76 moves upward, the two wedge sides of the balance frame
will push the slide frames to move toward a direction that makes
them more and more apart from each other until the movable contact
point 701 contact with the static contact points 101, thereby the
GFCI is closed. On the other hand, an end of the test piece 52 is
fixed in the corresponding groove of the middle body 20, and an
inner side of it is abutted against an outer side of the static
contact pieces 15,16. The other end of the test piece 52 is able to
resiliently contact the test resistor 53. When a test switch 50 is
pressed and the test piece 52 contacts with the test resistor 53,
if a man-made fault current is added on the GFCI according to the
invention, or else if a grounding fault exists in the load side and
the fault current reaches a threshold value, the control circuit
will energize the trip coil 72 instantly and produces an
electromagnetic force which acts on the plunger 74. As a result,
the plunger 74 will promptly drive the latch 75 to move, dislodge
the arc-shaped opening 12 on the latch 75 from the lock groove 11
in the resent pull rod 61, and push the movable contact points 701
away from the static contact points 101 under the help of a pair of
springs 78, thereby trip the GFCI.
[0032] FIG. 12 shows a general GFCI circuit of the present
invention. Diodes D1-D4 form a rectifying circuit, converting the
AC input to a DC output. A DC output terminal of the rectifying
circuit is connected to a resistor R2. The other end of R2 connects
with a capacitor C5. The other end of C5 is then connected to the
"ground". In the exemplary 20 A-rated GFCI device, an electrical
voltage of approximately 26V formed between the two ends of C5
serves as a DC voltage for the circuit.
[0033] The reset switch RESET, the breaking switch K, the resistors
R4 and R5, the capacitors C6 and C7, the SCR1, the trip coil 72
etc. form the reset control circuit. One end of the breaking switch
K is connected to R2, and the other end of the breaking switch K is
connected to R4 and C6. The other end of R4 and C6 is connected
with the gate pole of SCR1, R5 and C7. Capacitor C7 is connected
between the gate and cathode of the SCR1 to serve as a filter for
preventing noise pulses. One end of the trip coil 72 is connected
to the positive pole of SCR1, and the other end of the trip coil 72
is connected to the source end of the GFCI. One end of the reset
switch RESET is connected to the line terminal; the other end of
RESET is connected to the load terminal. It is noted that the
contact point between the reset switch RESET and the line terminal
corresponds to the movable contact points 701 of the movable
contact pieces, and the contact point between the reset switch
RESET and the load terminal corresponds to the static contact
points 101 of the static contact pieces. The power supply of the
control circuit is connected to the line of the GFCI, so when the
GFCI is energized, the control circuit of the GFCI is also
energized. When the breaking switch K is pressed, the capacitor C6
is charged up, generating a trigger signal to gate the SCR1 into
conduction. Consequently the trip coil 72 is energized
factitiously. That is, the trip coil 72 produces an electromagnetic
force to act on the plunger 74, causing the reset switch RESET to
close thereby reset the GFCI.
[0034] The IC may be a special integrated circuit for GFCI, for
example, of type RV4145A.
[0035] The two ends of a sensing coil of sensing transformer 83
connect to opposite ends of the capacitor C0. One end of the
sensing coil of sensing transformer 83 serially connects to the
capacitor C1, the resistor R3, and then the terminal 1 of the IC
(which, as discussed below, may include an amplifier circuit), and
the other end of the sensing coil of 83 connects to the terminal 3
of the IC, forming a transformer-coupled circuit that receives
differential voltage inputs. The feedback resistor, R1, connects to
the terminal 1 of the IC at one end and to the terminal 7 of the IC
at the other end. The magnitude of resistance at R1 determines the
amplification of the IC, that is, the threshold value for the
tripping action of the GFCI.
[0036] The neutral transformer 81, the capacitor C2, and the
capacitor C3 form the neutral ground-fault protection circuit. The
two ends of the sensing coil of neutral transformer 81 are
connected to opposite ends of the capacitor C2. One end of the
sensing coil of neutral transformer 81 is further connected to the
capacitor C3 and the other end of the sensing coil of neutral
transformer 81 is connected to the "ground". The other end of the
capacitor C3 is connected to the terminal 7 of the IC.
[0037] Given the above-described apparatus, neutral ground-fault
protection occurs as follows. The transformers 83 and 81 form a
sine wave oscillator with a corresponding transformer-coupled
oscillating frequency. When neutral ground fault occurs, this
oscillator starts to oscillate. When the magnitude of the
oscillation reaches the IC threshold value, then the terminal 5 of
the IC delivers a trigger signal, putting the tripper in motion and
the GFCI breaks.
[0038] The trip coil 72, the SCR2 and the capacitor C4 form a trip
control circuit. One end of the trip coil 72 is connected to the
line terminal of the GFCI, and the other end of the trip coil 72 is
connected to the positive pole of SCR2. The gate pole of SCR2 is
connected to the terminal 5 of the IC and the cathode of the SCR2
is connected to the "ground". The gate pole and the cathode pole of
the SCR2 are connected with opposite ends of the capacitor C4.
[0039] In operation, the sensing transformer 83 serves as a
differential transformer for detecting a current leakage between
the line side of the load terminal and an earth ground, while the
neutral transformer (N2) detects current leakage between the
neutral side of the load terminal and an earth ground. In the
absence of a ground fault condition, the currents flowing through
the conductors will be equal and opposite, and no net flux will be
generated in the core of the sensing transformer 83. In the event
that a connection occurs between the line side of the load side and
ground, however, the current flowing through the conductors will no
longer precisely cancel and a net flux will be generated in the
core of the sensing transformer 83. When the flux increases beyond
a predetermined value, it will give rise to a potential at the
output of the sensing transformer 83, which is applied to the
inputs 1 and 3 of the IC and trip circuit, and further amplified by
the IC to be sufficient to produce a trip signal on the output
terminal 5. The trip signal then gates the SCR2 into conduction,
energizes the trip coil 72 and puts the tripper in motion thereby
breaks the GFCI.
[0040] The test switch TEST and the current limiting resistor R0
form the test circuit. The current limiting resistor R0 is
connected to the power source, and the other end of resistor R0 is
connected to the test switch TEST. The other end of the test switch
TEST is connected to the other end of the load. The test circuit
constantly provides the GFCI a 8 mA fault current for periodically
checking of the working status of the GFCI.
[0041] The circuit shown in FIG. 10 also includes a metal oxide
varistor Mov connected across the input terminals of the AC power
source, in order to protect the whole control circuit from
transient voltage surges.
[0042] If the GFCI receptacle is inadvertently miswired by
connecting the line to the load, before the reset switch RESET
closes, the control circuit is de-energized. When the control
circuit is not energized, the reset pull rod 61 cannot pass through
the latch 75, thus the break switch cannot be closed. In other
word, the trip coil cannot produce a corresponding electromagnetic
force to act on the plunger 74, thereby keeping the GFCI also
de-energized, achieving the reverse wiring protection function.
[0043] In summary, the present invention provides a GFCI receptacle
that has reverse wiring protection function and the advantages of
tripping rapidly, operating conveniently, and reasonable
configuration.
[0044] While only the fundamental features of the present invention
have been shown and described, it will be understood that various
modifications and substitutions and changes of the form and details
of the device described and illustrated and in its operation may be
made by those skilled in the art, without departing from the spirit
of the invention.
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