U.S. patent application number 10/633451 was filed with the patent office on 2004-02-05 for overload protector with control element.
Invention is credited to Herrick, Kent B..
Application Number | 20040021994 10/633451 |
Document ID | / |
Family ID | 22483521 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040021994 |
Kind Code |
A1 |
Herrick, Kent B. |
February 5, 2004 |
Overload protector with control element
Abstract
A hermetic compressor is disclosed having an electric motor, a
compressor unit, and an overload protector within a hermetically
sealed housing. The overload protector includes a thermally
activated switching device for selectively providing current to the
electric motor, a heater element thermally coupled to the switching
device, and a control circuit controlling the heater element. The
overload protector allows the disconnection of power to the motor
due to factors and conditions specified in the remotely located
control circuit.
Inventors: |
Herrick, Kent B.; (Saline,
MI) |
Correspondence
Address: |
BAKER & DANIELS
111 E. WAYNE STREET
SUITE 800
FORT WAYNE
IN
46802
|
Family ID: |
22483521 |
Appl. No.: |
10/633451 |
Filed: |
August 1, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10633451 |
Aug 1, 2003 |
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10337521 |
Jan 7, 2003 |
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6639502 |
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10337521 |
Jan 7, 2003 |
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09586857 |
Jun 5, 2000 |
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6542062 |
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60138760 |
Jun 11, 1999 |
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Current U.S.
Class: |
361/26 |
Current CPC
Class: |
H01H 37/004 20130101;
H01H 61/02 20130101; H01H 2037/5463 20130101; H01H 61/002
20130101 |
Class at
Publication: |
361/26 |
International
Class: |
H02H 005/04; H02H
007/08 |
Claims
What is claimed is:
1. An overload protector coupled to an electric motor comprising: a
thermally activated switching device for selectively providing
current to a mains circuit of the electric motor, said switching
device including a first heater element; a second heater element
thermally coupled to said switching device; and a control circuit
connected to and activating said second heater element.
2. The overload protector of claim 1 in which said switching device
comprises a bimetallic element.
3. The overload protector of claim 1 in which said control circuit
is remotely located relative to said motor.
4. The overload protector of claim 1 further comprising a second
heater element thermally coupled to and electrically connected in
series with said switching device.
5. A hermetic compressor comprising: a hermetically sealed housing;
an electric motor disposed in said housing and having a stator and
rotor; a compressor unit disposed in said housing and driven by
said motor; and an overload protector comprising: a thermally
activated switching device for selectively providing current to
said electric motor, said switching device including a first heater
element; a second heater element thermally coupled to said
switching device; and a control circuit connected to and activating
said second heater element.
6. The hermetic compressor of claim 5 in which said electric motor
is a single phase electric motor.
7. The hermetic compressor of claim 5 in which said electric motor
is a three phase electric motor.
8. The hermetic compressor of claim 5 in which said electric motor
is a permanent split capacitor motor.
9. The hermetic compressor of claim 5 in which said electric motor
is a repulsion-start, induction-run motor.
10. The hermetic compressor of claim 5 wherein said control circuit
is disposed externally of said housing.
11. The hermetic compressor of claim 5 wherein said overload
protector includes a second heater element thermally coupled to and
electrically connected in series with said switching device.
12. A hermetic compressor comprising: a hermetically sealed
housing; an electric motor disposed in said housing and having a
plurality of windings; a compressor unit disposed in said housing
and driven by said motor; a contactor module electrically connected
to said electric motor and having a thermally activated switching
device for selectively providing current to said electric motor and
at least one heater element thermally coupled to said switching
device; and a control assembly electrically connected to said
contactor module and having a heater element control circuit for
activating said heater element.
13. The hermetic compressor of claim 12 wherein said contactor
module includes a relay for controlling said heater element and
said heater element control circuit includes a relay controller for
operating said relay.
14. The hermetic compressor of claim 12 wherein said contactor
module includes current sensors and said control assembly includes
a current sensor circuit for determining current to said electric
motor.
15. The hermetic compressor of claim 12 further comprising a oil
sensor, said control assembly including a low oil sensor circuit
electrically connected to said oil sensor for determining a low oil
condition.
16. The hermetic compressor of claim 12 wherein said control
assembly includes a microprocessor.
17. The hermetic compressor of claim 12 wherein said control
assembly includes an input/output interface circuit for
transmitting information from and receiving information to said
control assembly.
18. The hermetic compressor of claim 12 wherein said control
assembly is remotely located.
19. The hermetic compressor of claim 12 wherein said contactor
module includes at least one inductive pickup and said control
assembly includes a winding sensor circuit electrically connected
to said inductive pickup for determining the condition of said
windings.
Description
BACKGROUND OF THE INVENTION
[0001] Existing overload protectors in hermetic compressors use a
combination of a heating element and a bimetallic switching device
to break the motor circuit if current or temperature limits are
exceeded. In a locked rotor condition a current trip will be
primarily driven by I.sup.2R losses through the heater, while a
running high temperature trip is more influenced by the ambient
temperature. With either influence, the temperature reaches a point
such that the bimetallic switching device "snaps" into a new
position, thus breaking the circuit.
[0002] Typical devices used in motor applications for temperature
and/or current protection include those as disclosed in U.S. Pat.
No. 3,167,699 (Renaud), U.S. Pat. No. 5,615,072 (Hofsass et al),
U.S. Pat. No. 5,575,229 (Takeda), and U.S. Pat. No. 4,866,408
(Petraitis et al) and commercially available hermetic motor
protectors from Texas Instruments, Inc. of Dallas, Tex. given
product designation 33HM800 or the like.
[0003] The heaters in the above mentioned devices connect in series
with the mains circuit of a motor. When the current in the mains
circuit increases to a level above the specified maximum current
limit for the motor, the heat generated by this level of current
through the heater will be adequate to trip the bimetallic
switching device and open the mains circuit.
SUMMARY OF THE INVENTION
[0004] The present invention provides for the use of a control
element powered and/or controlled from a separate control circuit.
In one embodiment heating the bimetallic switching device with this
control element, the circuit can be broken on command from a
control signal, independent of the mains power conditions. In
another embodiment a control element and a normally closed switch
are connected in parallel with the mains power circuit. The switch
is operated by a control signal. When the switch is closed and the
mains circuit is powered, the mains circuit will be broken. Unlike
prior motor protectors, which include heaters not independently
controlled, the present invention incorporates at least one heater
which is operatively connected to a control circuit for controlled
actuation of the protective device.
[0005] One advantage of the present invention is that the circuit
can be broken from a control signal, independent of the mains power
condition. The control signal will allow the circuit to be broken
due other factors or conditions other than the exceeding of current
or temperature limits.
[0006] Another advantage of the present invention is that with the
inclusion of current and temperature monitoring devices into the
control circuit, the heating element for the current protection in
the overload protector could be eliminated and the overload
protector would not have to be located in such an extreme
environment to detect the temperature trip level.
[0007] Another advantage of the present invention is that it does
not require a large heat sink as would a silicon rectifier.
[0008] Another advantage of the present invention is that power
must be applied to the control circuit and no trip conditions
sensed before the motor can be operated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The above mentioned and other advantages and objects of this
invention, and the manner of attaining them, will become more
apparent and the invention itself will be better understood by
reference to the following description of embodiments of the
invention taken in conjunction with the accompanying drawings,
wherein:
[0010] FIG. 1 is a schematic block diagram of the basic
representation of the first embodiment of the present
invention;
[0011] FIG. 2 is a typical circuit diagram of the first embodiment
of the present invention in a single phase configuration for a
permanent split capacitor motor;
[0012] FIG. 3 is a typical circuit diagram of the first embodiment
of the present invention in a single phase configuration for a
repulsion-start, induction-run (RSIR) motor;
[0013] FIG. 4 is a typical circuit diagram of the first embodiment
of the present invention in a three phase configuration;
[0014] FIG. 5 is another typical circuit diagram of the first
embodiment of the present invention in a three phase
configuration;
[0015] FIG. 6 is an example of the present invention in hermetic
motor protector 33HM800 from Texas Instruments;
[0016] FIG. 7 is a schematic block diagram of the basic
representation of the second embodiment of the present
invention;
[0017] FIG. 8 is a typical circuit diagram of the second embodiment
of the present invention in a single phase configuration for a
permanent split capacitor motor;
[0018] FIG. 9 is a typical circuit diagram of the second embodiment
of the present invention in a single phase configuration for a
repulsion-start, induction-run (RSIR) motor;
[0019] FIG. 10 is a typical circuit diagram of the second
embodiment of the present invention in a three phase
configuration;
[0020] FIG. 11 is another typical circuit diagram of the second
embodiment of the present invention in a three phase
configuration;
[0021] FIG. 12 is a schematic block diagram of compressor control
system having a control circuit and using the second embodiment of
the present invention; and
[0022] FIG. 13 is an installed view of the compressor control
system of FIG. 12.
[0023] Corresponding reference characters indicate corresponding
parts throughout the several views. Although the drawings represent
embodiments of the invention, the drawings are not necessarily to
scale, and certain features may be exaggerated or omitted in
selected drawings in order to better illustrate and explain the
present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0024] The first embodiment of the present invention as shown in
FIG. 1 provides a circuit control device 10, that may be a
component of a hermetic compressor 8, for example, which device 10
includes a heating element 18 coupled to the mains circuit of the
compressor stator 32, a bimetallic switching device 16, and a
control heating element 12 powered from a separate control circuit
14. Control element 12 and heating element 18 are adjacent to and
in thermal contact with bimetallic switching device 16. The mains
circuit, heating element 18 and bimetallic switching device 16 are
connected in series to a power line L1, L2 and via external
connectors 22 and 24. Control element 12 is connected to external
connectors 28 and 30. Control circuit 14 is connected to control
element 12 via external connectors 28 and 30.
[0025] The second embodiment of the present invention as shown in
FIG. 7 provides circuit control device 50, that may be a component
of hermetic compressor 8, for example, which device 50 includes
heating element 18 coupled to the mains circuit of compressor
stator 32, bimetallic switching device 16, control heating element
52, and normally closed switch 56 operated from separate control
circuit 54. Control element 52 and heating element 18 are adjacent
to and in thermal contact with bimetallic switching device 16. The
mains circuit, heating element 18 and bimetallic switching device
16 are connected in series to a power line L1, L2 and via external
connectors 22 and 24. Control element 52 and switch 56 are
connected in parallel to the mains circuit. Switch 56 is connected
to external connectors 68 and 70. Control circuit 54 is connected
to switch 56 via external connectors 68 and 70.
[0026] The present invention can be used in a hermetic compressor,
as just one example. Overload and overheating protection along with
control due to other desired factors or conditions is offered by
the present invention. One hermetic compressor, which is applicable
to use with the present invention, is disclosed in U.S. Pat. No.
5,785,15 1, which is assigned to the assignee of the present
invention, the disclosure of which is explicitly incorporated by
reference.
[0027] FIG. 1 shows a schematic block diagram of a hermetic
compressor 8 with a first external connector 22 and a second
external connector 24 through which electrical power is supplied to
circuit control device 10 connected in series with controlled
device 32, for example the electric motor of a compressor. Circuit
control device 10, a first embodiment of the present invention,
consists of heating element 18 coupled to the mains circuit,
bimetallic switching device 16, and control element 12 powered from
separate control circuit 14. Control circuit 14 enables opening or
closing of switch 16 for conditions other than overheating or
overloading.
[0028] Control circuit 14 contains circuitry for monitoring motor
current and high/low voltage conditions. In addition, a sensorless
temperature measurement scheme may be employed to protect the motor
winding from overheating in any running condition. Provisions may
be made to output current, temperature and trip information to an
optional externally mounted circuit board that could be linked to
an HVAC central control system.
[0029] If bimetallic switching device 16 senses a temperature below
its release temperature bimetallic switching device 16 completes
the connection with contact 26 so that the operating current flows
through the electric part, for example, stator windings 32. If the
temperature of bimetallic switching device 16 now rises, due either
to an increase in temperature of the electrical part to be
monitored or to an excess operating current through heating element
18, which heats up correspondingly, bimetallic switching device 16
opens when it exceeds its release temperature. Bimetallic switching
device 16 can also be opened when logic in control circuit 14
allows sufficient current to flow through control element 12, which
heats up correspondingly, causing the temperature of bimetallic
switching device 16 to exceed its release temperature. The opening
of bimetallic switching device 16 interrupts the flow of current
through the electric part.
[0030] FIG. 2 shows a schematic diagram of the first embodiment of
the present invention in a single phase configuration for a
permanent split capacitor motor used in a hermetic compressor, for
example. The present invention provides internal protection for one
to five horsepower motors, typically used in the compressors of
commercial refrigerators, unitary air conditioners and heat pumps.
The heater in the mains circuit may not be required depending on
the application. Split motor capacitor motor 32 includes main
winding 34, start winding 36, and capacitor 38. Circuit control
device 10 comprises bimetallic switching device 16, heaters 18, and
control element 12 coupled to control circuit 14 via pins 28 and
30. Either heaters 18, control element 12 or ambient temperature
can activate switch 16 and shut down motor 32.
[0031] FIG. 3 shows a schematic diagram of the first embodiment of
the present invention in a single phase configuration for a RSIR
motor. The present invention provides external protection for
fractional horsepower motors, typically used in the compressors of
residential refrigerators and room air conditioners. The heater in
the mains circuit may not be required depending on the application.
RSIR motor comprises main winding 34, start winding 36, and start
resistor 40. Circuit control device 10 includes bimetallic
switching device 16, heater 18, and control element 12 coupled to
control circuit 14 via pins 28 and 30. Motor 32 can be shut down by
the activation of switch 16 by the ambient temperature, heater 18,
or control element 12.
[0032] FIGS. 4 and 5 show schematic diagrams of the first
embodiment of the present invention in three phase configuration.
The heater or heaters in the mains circuit may not be required
depending on the application. Three phase motors 32 contain three
windings 42, 44, 46. Circuit control device 10 comprises bimetallic
switching device 16, heaters 18, and control, element 12 coupled to
control circuit 14 via pins 28 and 30. In both cases the current to
motors 32 can be interrupted by the ambient temperature, heaters
18, or control element 12 causing bimetallic switch 16 to open.
[0033] FIG. 6 shows an example of the first embodiment of the
present invention in hermetic motor protector 33HM800 from Texas
Instruments. Circuit control device 10 includes bimetallic
switching device 16, heater 18, and control element 12 coupled to
control circuit 14 via pins 28 and 30. Switching device 16 can be
activated by the ambient temperature, heater 18, or control element
12.
[0034] FIG. 7 shows a schematic block diagram of a hermetic
compressor 8 with a first external connector 22 and a second
external connector 24 through which electrical power is supplied to
circuit control device 50 connected in series with controlled
device 32, for example the electric motor of a compressor. Circuit
control device 50, a second embodiment of the present invention,
consists of heating element 18 coupled to the mains (NC switch)
circuit, bimetallic switching device 16, control element 52, and
normally closed switch 56 operated from separate control circuit
54. Control circuit 54 enables opening or closing of switch 16 for
conditions other than overheating or overloading.
[0035] Control circuit 54 contains circuitry for monitoring motor
current and high/low voltage conditions. In addition, a sensorless
temperature measurement scheme may be employed to protect the motor
winding from overheating in any running condition. Provisions may
be made to output current, temperature and trip information to an
optional externally mounted circuit board that could be linked to
an HVAC central control system.
[0036] If bimetallic switching device 16 senses a temperature below
its release temperature, bimetallic switching device 16 completes
the connection with contact 26 so that the operating current flows
through the electric part, for example, stator windings 32. If the
temperature of bimetallic switching device 16 then rises
sufficiently, due either to an increase in temperature of the
electrical part to be monitored or to an excess operating current
through heating element 18, which heats up correspondingly,
bimetallic switching device 16 opens when it exceeds its release
temperature. Bimetallic switching device 16 can also be opened when
logic in control circuit 54 closes switch 56 and allows current to
flow through control element 52, which heats up correspondingly,
causing the temperature of bimetallic switching device 16 to exceed
its release temperature. Control element 52 is sized to immediately
cause bimetallic switching device 16 to open if current is applied
to control element 52. Normally closed switch 56 will only open if
power is applied to control circuit 54 and no trip conditions are
set. The opening of bimetallic switching device 16 interrupts the
flow of current through the electric part.
[0037] FIG. 8 shows a schematic diagram of the second embodiment of
the present invention in a single phase configuration for a
permanent split capacitor motor used in a hermetic compressor, for
example. The present invention provides internal protection for one
to five horsepower motors, typically used in the compressors of
commercial refrigerators, unitary air conditioners and heat pumps.
The heater in the mains circuit may not be required depending on
the application. Split motor capacitor motor 32 includes main
winding 34, start winding 36, and capacitor 38. Circuit control
device 50 comprises bimetallic switching device 16, heaters 18,
control element 52 and NC switch 56 coupled to control circuit 54
via pins 68 and 70. Either heaters 18, control element 52 or
ambient temperature can activate switch 16 and shut down motor
32.
[0038] FIG. 9 shows a schematic diagram of the second embodiment of
the present invention in a single phase configuration for a RSIR
motor. The present invention provides external protection for
fractional horsepower motors, typically used in the compressors of
residential refrigerators and room air conditioners. The heater in
the mains circuit may not be required depending on the application.
RSIR motor comprises main winding 34, start winding 36, and start
resistor 40. Circuit control device 50 includes bimetallic
switching device 16, heater 18, control element 52, and NC switch
56 coupled to control circuit 54 via pins 28 and 30. Motor 32 can
be shut down by the activation of switch 16 by the ambient
temperature, heater 18, or control element 52.
[0039] FIG. 10 shows a schematic diagram of the second embodiment
of the present invention in three phase configuration. The heater
or heaters in the mains circuit may not be required depending on
the application. Three phase motor 32 contains three windings 42,
44, 46. Circuit control device 50 comprises bimetallic switching
device 16, heaters 18, control element 52, and normally closed
relay 60 coupled to control circuit 54 via pins 28 and 30. Control
element 52 includes three heating elements 62, one for each of
windings 42, 44, 46. The current to motor 32 can be interrupted by
the ambient temperature, heaters 18, or control element 52 causing
bimetallic switch 16 to open.
[0040] FIG. 11 shows a schematic diagram of the second embodiment
of the present invention in another three phase configuration.
Three phase motor 32 contains three windings 42, 44, 46. Control
circuit 50 comprises bimetallic switching device 16, control
element 52 and normally closed relay 60 coupled to control circuit
54,via pins 28, 30. Control element 52 includes three heating
elements 62, one for each of windings 42, 44, 46. The current to
motor 32 can be interrupted by the ambient temperature or control
element 52 causing bimetallic switch 16 to open.
[0041] FIG. 12 shows an application of the second embodiment of the
present invention in a compressor control system. The compressor
control system includes main power terminal 6, compressor 8,
contactor module 66, and circuit control 54. Compressor 8 includes
low oil sensor 68. Contactor module 66 includes bimetallic switch
16, heater element 58, NC relay 60, current sensor 70, an inductive
pickup 72, and external connector 74. Control circuit 54 includes
I/O interface circuit 80, relay control circuit 82, current sensor
circuit 84, winding sensor circuit 86, transformer 88, power supply
90, microprocessor 92, cool control and low oil sensor circuit 94,
and external connector 96.
[0042] FIG. 13 shows a view of contactor module 66 and circuit
control 54 installed to compressor 8.
[0043] Circuit control 54 receives information from current sensors
70, inductive pickup 72, oil sensor 68, and HVAC interface 76.
Using I/O interface 80, current sensor circuit 84, winding sensor
circuit 86, cool control and oil sensor circuit 94, and
microprocessor 92, control circuit 54 controls normally closed
relay 60 through relay control circuit 82.
[0044] Bimetallic switching device 16 described above can be a
current carrying device or a non-current carrying device coupled
mechanically to a connector piece containing switching
contacts.
[0045] This concept could be used in a variety of configurations
including, but not limited to, the following:
[0046] single phase or three phase mains power supply
[0047] bimetallic switching device normally open or normally
closed
[0048] mains fed heater plus an additional control element
[0049] control element without mains fed heater
[0050] mains fed heater with additional current superimposed by
control circuit in order to raise temperature to release point
[0051] as an internal (hermetically sealed type) or external
device
[0052] The present invention may be further modified within the
spirit and scope of this disclosure. This application is intended
to cover departures from the present disclosure as come within
known or customary practice in the art to which this invention
pertains.
* * * * *