US2278575A - Control for electric motors - Google Patents

Description

April 1942- c. .1. WERNER ETAL 2,278,575

CONTROL FOR ELECTRIC MOTORS Filed Oct. 13, 1939 INVENTORS 53 CHI-VIN J. WERNER (9N0 34 ATTORNEYS I Patented Apr. 7, 1942 con'raor. roa ELECTRIC Morons Calvin]. Werner and William E. Menzies, Dayton, Ohio, assignors to General Motors Corporation,

Detroit, Mich, a corporation of Delaware Application October 13, 1939, Serial No. 299,254

11 Claims.

The invention relates to improvements in electrical control devices particularly adapted for use with electric motors providing motive power for refrigeration or air conditioning apparatus.

It is among the objects of the present invention to provide a device of simple structure and design adapted to control the starting of an elec-' tric motor, protect it against damages by overload or abnormal running conditions and also to control operation oi. the motor in response to and in accordance with variations in temperature remote from said motor.

Simplicity of design and the required circuits are attained by providing a single control switch adapted to be rendered efiective to control the motor in accordance with current conditions duringthe starting and running periods of said motor and also in accordance with variations in temperature remote from said motor.

Further objects and advantages of the present voltage coil of which is directly connected across the thermal actuatorof the switch.

Fig. 2 ditfers from Fig'. 1 in the elimination of the transformer and the provision of a heater coil about the thermal member of the switch.

Fig. 3, like Fig. 1. illustrates the use of a transformer, however, in Fig.v 3, the low voltage coil of the transformer is connected in circuit directly withthe thermal element of the device.

Referring to the drawing, the numeral designates the motor having a starting winding 2i and a running winding 22. An end of each winding 2i and-22 is connected through wire 23 with the main power supplyline 24., The numeral 25 designates the other power supply line. A wire 23 connects the other end of the starting winding 2| with the stationary contact 3| of the thermal switch 30. A condenser 21 is shown in the line 26. The other end of the running winding 22 is connected by wire 23 with the stationary contact 32 ofswitch 30.

The thermo-electric switch comprises a main body portion 33 pivotally carried by stud 34.

' A tension spring 35 is secured at one end'to an extension of switch body 33, the other end of the spring being anchored to the stationary pin 36.- Another extension of body 33 has one end of a thermal element 31 attached thereto, the op- 1 posite end of said thermal element being secured spring 45. On the other hand is expansion of thermal element 31 permits spring 33 to rotate spring body 33 clockwise. sufliciently, spring 45- will-urge arm 42 toward contact 3 i. v 1

I A second arm ill hingedly seats in notch 41 and has a contact ii cooperating with stationary contact 32. A spring 53 is adapted to shift arm Bl between contact 32 anda stop pin 54 dependent upon movement of spring body 33.

An electric translating device in the form of a transformer has one end of itsprimary coil 6i connected to the power supply line 24, the other.

end to a stationary contact II. The secondary coil 62 has its one and connected to the thermal element as at 63 by wire 84, which wire also is connected to the power supply line 25. The other, end of secondary coil 62 is connected to the end of thermal element, 31 opposite the'adjusting nut 38. Thus current from coil 62 must flow through the thermal element 31.

The means for controllingv the flow of current through the primary winding 6| of the transformer comprises the stationary contact ll adapted to be engaged by the contact 12 carried by the thermal member 13. One end of this thermal member 13 is anchored as at I4. A heater coil I5 is associated with the member 13, one end of said heater being electrically connected to said member 13, theother end to the Dower supply I this, what may be termed reference temperawith the present invention, is used to drive air conditioning apparatus, the regulator including the thermal member 13, is placed within the room or chamber in which the temperatures are to be controlled. Under these circumstances the mem ber will be flexed initially so that its contact 12 will engage contact 1| at the desired reference temperature," say at about 80 F. Variation in temperature from this reference temperature will affect the regulation in the manner aforedescribed.

The apparatus of Fig. l operates in the following manner:

When switch 30 is in the position as shown and power lines 24 and 23 are closed by switch 8|, current will flow from power line 24 through wire 23 to both motor windings 2| and 22. Current flowing through the motor starting winding 2| will continue through wire 26, condenser 21 to the stationary contact 3| of switch 30, thence into contact 43, engaging contact 3|, through arm or blade 42 into the body 33 of the switch, through thermal conductor or element 31 to the point 63 where wire 64 is electrically connected to said element 31. Wire 64 is connected to the other power supply line 25 by switch 8|. This completes the circuit through the starting winding 2| of the motor.

The running winding circuit is completed as follows: from wire 23 through the running winding 22, wire 28, contacts 32 and SI, arm or blade 30 and thence back to the other power supply line through the switch body 33, thermal element or conductor 3|, connection 33 and wire 33.

With both windings 2| and 22 so energized, motor 20 will start to operate. The first surge of current through the motor will be somewhat heavy and thus thermal element 31 carrying this surge of current will become heated, resulting in a predetermined expansion of said element. As element 31 expands, spring 35 becomes effective to rotate switch body 33 clockwise about its pivot pin 33. The contact arms or blades 42 and 50 are so arranged on the switch body 33 and relatively to their respective stop pins 44 and t and contacts 3| and 32 that as a result of a predetermined rotation clockwise oi the switch body 33, contact arm or blade 42 will first be moved to disengage its contact 33 from the stationary contact 3|. Further rotation of said body 33 clockwise will result in movement of contact arm 50 to disengage its contact ill from contact 32. The element 31 is so designed that it will expand during the starting period of the motor, only suiflciently to permit spring 35to rotate body 33 far enough to actuate contact arm 42 to circuit breaking position. Thus the starting circuit through winding 2| is broken. Current flowing through the thermal element 31 during the normal running of the motor is insuflicient to heat up said element so that it will further expand and permit spring 33 to rotate the switch body 33 and actuate contact arm 30 to open circuit conditions.

position. This takes place only when an abnormal running condition occurs or when the motor is overloaded or stalled at which time an abnormal flow through thermal element 31 results in increased heating and consequent expansion thereof. As the element 31 cools and consequently contracts, it will rotate the switch body counter-clockwise, resulting in a substantial simultaneous movement oi arms 32 and 50 to their circuit closing positions. Thus it may be seen that switch 30 simultaneously closes the starting and running circuit contacts and successively opens them in accordance with the flow of current through the thermal element thereof.

This switch 30 of the present invention is adapted not only to control the starting and running of the motor, but it also provides protection for the motor under abnormal running Still another characteristic of the switch 30 is to control the motor in response to and in accordance with variations in temperature at the region designated by the dot-and dash line 30. When the temperature at 8|] is brought to and below the chosen reference temperature of 40 F., contact arm 13, as has been previously mentioned, will flex to urge its contact 12 into engagement with contact 1i, thus completing the circuit from power line 24 through the primary winding 6| of the transformer, across contacts 1| and 12, member 13, heater coil 15 and back to the power supply line 25. This circuit will remain closed until the heater coil 15 radiates sufficient heat to overcome the effect of the lower ambient temperature and cause flexing of the thermal element to disengage its contact 12 from contact 1|. Now thermal element 13 may cool of! and again flex to close the circuit. It may clearly be seen that this operation of the thermal element 13 is repeated providing for intermittent closing of the primary circuit of the transformer. Naturally intermittent closing of the primary circuit causes the secondary circuit to provide intermittent cur- I rent flow through the circuit which includes the thermal switch actuating element 3i. When the closing intervals of contacts 1| and 12 are of suflicient duration due to lowering temperatures at the ambient region 30, secondary coil 52 will provide, sumcient current flow through thermal .element 31 to heat it, causing expansion thereof so that spring 35 may actuate the switch to open the motor circuits and "thus cause cessation of motor operation.

When the temperature ambient to the control device comprising contacts "H and it and thermal element 13 increases, said device will. be affected to decrease the energy passing through the circuit including said device and thermoelectric element 31. when this energy level reaches the reset valve oi switch 33. the switch will operate to close the motor circuits and again establish refrigeration.

The construction shown in Fig. 2 differs from that of Fig. l in that no transformer is used. Here the one power supply line M has a wire 82 leading from it to the one end of a heater coil 83 about thermal element 31', the other end of said coil having a wire 33 connecting it to the stationary contact 1|. Thus each time contacts 1| and 1'2 are closed, current will flow from the power supply line 24 through wire 32 direct to and through the heater coil 33, wire 34, contacts 1| and 12, thermal element 13, heater coil 15 back to the other power supply line 25 via the wire 35. It will be understood, however, that thermal elecomplete the circuit through heater coil II. The I engagement 01' contacts II and I! must be oi a predetermined interval to causeproper energization or the heater coil ll, so that it will radiate suflicient' heat to efiect the expansion oi thermal element 31 and resultant switch operation.

In the Fig. 3 a modiiied term of the invention is illustrated. Here the transiormer III has its primary winding 81 connected in circuit with the power supply line switch II by wires 8! and I". The secondary, low voltage winding ll of said transformer has one end connected through wire 92 to the adjusting nut ll electrically engaging one end of the thermal element 31. The other end or the secondary-winding I! has a wire II connecting it with the thermal element ll of the current regulator, which element carries a contact fl! cooperating with stationary contact Ii. Wire 94 connects contact Ii with the end of thermal element 3! remote from the adjusting nut. thermal element 13 i eliminated, the thermal element itseli'heating up and ilex'ing due to the how or current through it. The motor windings 2| and 22 are connected to one side of switch ll through wires 80 and I.

From the aioregoing description the device of the present invention comprises a single switch for controlling the circuits of the driving motor. This switch hasione thermal element, aflected by the current flow therethrough, to actuate the switch. Current flow during the starting period 4 oi the motor sheets the thermal element to open only the starting winding. Abnormal current ilow due to overload, stalling of the motor or abnormal motor requirements aflects said thermal element to actuate the switch to break the running circuit 0! the motor., In addition to this, the device, also has means providing anadditional or separate current flow through the thermal element of the switchwhlch attects said element to actuate the switch to control the motor circuits in accordance with and response'to variations in temperature at a region remote from said motor.

While the embodiment of the present invention as herein disclosed constitutes a preferred 1 form, it is to be; understood that other forms might be adopted, all coming within the scopeoi the claims which follow. What is claimed is as iollows:

1. In a device of the character described, the

combination with an electricmo'tor having a starting and a running circuit, a'switch adapted to control said circuits; energy translating means independent of the electric motor controlled by variations in temperature ambient thereto and remote from the motor; and means for actuating said switch, said means being rendered eflective by current now through both motor circuits and by the energy translating means.

2. In a device of the character described, the combination with an electric motor having starting and running circuits; a switch for controlling said circuits; means independent of and remote from the motor adapted to provide electrical impulses in accordance with temperature conditions ambient to said means; and an electro-thermal element for actuating said switch, said element being rendered eilective by current flow through the motor circuits and also by the electrical im- I pulses provided by the temperature controlled means.

In this instance the heater coil II about translating device; means remote .irom both the motor and the energy translating device for controlling the eflectiveness oi said device in accordance with variations in temperature ambient to said means; and a. switch for controlling the motor, having means rendered eilective to actuate said switch by either predetermined ilows of current through the motor or the energy translating device.

4. Control apparatus for an electric motor having starting and running circuits; aswitch in said circuits; thermo-electric means for actuating said switch in accordance with the how of current through said circuits; means adapted separately to energize said thermo-electric means to actuate the switch; and a thermal circuit control device remote from the motor and unail'ected thereby for regulating said energizing means-in accordance with temperatures varying from a, predetermined mean temperature.

5. Control apparatus for an electric motor having starting and running windings; a switch for opening and closing the circuits through both said windings; a temperature responsive actuator for said switch, in circuitwith both said-windings and rendered effective by variations in currentilow through said windings;-and means separate from the motor, for providing a flow of current to effect said temperature responsive ac- .tuator, said means comprising a temperature responsive make and break device remote from and independent of the motor adapted to control current how in accordance with variations'in temperature ambient thereto.

6. Control apparatus for .an electric motor having starting and running windings; a switch having a thermal element in circuit with both windings of the motorand adapted in response to predetermined current flows therethrough to actuate the switch to control the starting circuit and to provide overload protection to the motor; and a separate circuit independent of and remote from the motor and including a thermal regulator connected to the thermal element and adapted to control said element in response'to and accordance with variations in temperature ambient to said regulator. I

7. Control apparatus for an electric motor having'startingand running windings; a switch having a thermal element in circuit with both windings oi the motor and adapted in response to predetermined current flows therethrough to actuate the switch to control the starting circuit and to provide overload for pro-.

tection to the motor; and a separate circuit independent of the motor circuits for affecting said thermal element, said circuit including an electric regulator remote from the motor and comprising a thermal member and a heater coil, adapted to control said thermal element to actuate the switch in response to variations in temperature ambient thereto, the eilect of said heater coil being a function of the difference between the reference temperature of said thermal member and the temperature ambient thereto.

8. Control apparatus for an electric motor having starting and running windings; a switch having a thermal element in circuit with both windings of the motor and adapted in response to motor circuits adapted to effect operation of the switch by the thermal element, said circuit including a thermal member and a heating coil remote from the motor adapted in response to variations of temperature ambient thereto to provide recurrent electrical impulses in said separate circuit.

9. Control apparatus for an electric motor having starting and running circuits adapted to be connected to a, source of electrical energy; a switch in said circuits; thermo-eleotric means for actuating said switch to 'control the motor in accordance with the flow of current through said circuits; a transformer having a primary and a secondary winding, one winding being connected to the thermo-electric means adapted to energize said means to actuate the switch; and a thermal switch remote irom the motor and said means and in circuit with the other winding oi the transformer and the source of electrical energy for controlling this circuit of the transformer to regulate its eflect in accordance with varying temperatures ambient to said thermal switch.

10. Control apparatus for an electric motor having starting and running circuits adapted to be connected to a source of electrical energy; a switch in said circuits; thermo-electric means for actuating said switch to control the motor in accordance with current flow therethrough; a transformer having primary and secondary circuits, one of these circuits being connected to sive to a predetermined temperature ambient thereto to connect its transformer circuit with the source of electrical energy and in response to a predetermined; comparatively higher ambient temperature to effect deenergization of said transformer by opening the circuit.

11. Control apparatus for an electric motor having starting and running windings adapted to be connected to a source of electrical energy; a switch having a thermal element in circuit with both windings of the motor and adapted in response to predetermined current flows therethrough to actuate the switch to control the starting winding circuit and to provide overload protection to the motor; a transformer having primary and secondary windings, the secondary winding being connected with the thermal element and adapted to energize it for eifecting actuation of the switch to stop the motor; and a temperature responsive switch remote from the motor and connected with the primary transformer winding and with the source of electrical energy, said temperature responsive switch acting in response to temperature variations ambient thereto to make or break the said primary transformer winding circuit.

CALVIN J. WERNER. WILLIAM E. MENZIES.

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