US2321798A - Motor starter - Google Patents

Description

June 15, 1943. H. P. CHANDLER ETAL MOTOR STARTER Filed Oct. 25. 1941 $5 FETY 6000110 #1071: F/MMI/ 0 H M M w CV0 M U H4! attorney Patented June 15, 1943 MOTOR STARTER Homer P. Chandler, deceased, late of Mansfield, Ohio, by Lillian 0. Chandler, administratrix', Mansfield, Ohio. assignor to The Ohio Brass Company, Mansfield, Ohio Application October 25, 1941, Serial No. 416,564

11 Claims.

This invention relates to motor starters and in its more specific aspects relates-to a starter in which the starting resistance is shunted out after the lapse of a predetermined time interval.

The object of this invention is to construct a motor starter in which the starting resistance will be shunted out of the motor circuit a predetermined time interval after the starting switch has been closed.

Another object of the invention is to construct a starter which will definitely remove the starting resistance from the motor circuit a pre determined time after closing the starting switch to prevent burning out the motor or starting resistance.

Other and further objects are to impose full line voltage on the motor terminals after a predetermined period of time following starting, to simplify construction and to render certain the removal or shunting out of the starting resistance upon completion or closing of the starting circuits.

Other and further objects of the invention will occur to those skilled in the arts to which this invention pertains as the description proceeds which taken in connection with the accompanying drawing sets forth a preferred embodiment of the invention but such disclosures are not to be construed as a limitation of the invention which is limited only by .the appended claims and any and all modifications, alterations and variations of structure coming'within the spirit and scope thereof are deemed to be in cluded herein.

In the drawing:

Fig. 1 shows a circuit diagram of a motor starter incorporating the invention.

Fig, 2 shows a sectional view of a time delay switch incorporated in the circuit of Fig. 1.

The motor starting art includes various devices for shunting out starting resistance which involve manual actuation to shunt out or remove sections of the resistance in order to bring the motor up to speed and other devices, well known to the arts, in whichv the starting resistance is shunted out in progressive steps by means of a plurality of contactors and still other devices combine time delays and periodic contactors for shunting out a motor starting resistance but all of the foregoing devices fail to take into consideration the desirable function of bringing full voltage across the motor terminals a predetermined time after' the starting switches have been closed. In line with the foregoing and with the stated objects of the invention, the 55 instant invention provides a circuit in whichthe starting resistance is shunted out of the motor circuit a predetermined time after the switches have been closed irrespective of the amount of power that is being drawn by the motor, the speed of the motor or the load that is imposed thereon.

The invention is embodied in the circuit outlined in the attached drawing in which I and 2 designate incoming lines incorporating a switch 3 of the more or less conventional design. The conductor 4 is connected between the switch 3 and one of the terminals of a thermo-relay. The field circuit of the motor includes the conductor 4, contact 8, thermo-element 6, conductor 9, contact I5, contactor arm I6, conductor ll, field l8, and conductor l9 terminating on the conductor 2. This circuit, which includes the breaker I4 has incorporated therein the thermoswitch element 6 and constitutes the fixed field circuit of the motor and its opening and closing is dependent upon the contactor arm of thermorelay I4 that has just been described.

The armature circuit, under conditiogns of starting, includes the conductor 4, the thermoelement 6 and its contact 8, conductor 9, the contactor elements l5 and I6, conductor 21, conductor 28, starting resistance 29, conductor 3| and motor armature 48, which is directly connected to the incoming conductor 2.

Each of the several control elements of the motor circuit incorporates a holding circuit for keeping the circuit breaker H in a closed position and the time delay switch 22 which has the elements thereof placed in a series relationship with the holding coil I4a of contactor l4. The holding circuit for the several contacts under starting conditions includes the switch 3, conductor 4, conductor 5, the low current jumper or connector I0, conductor 20, the coil or current consuming device 14a of circuit breaker I4, conductor 2|, conductor 23, the switch element 25 of the time delay 22, conductor 24, thence leading to coil 26 over a portion of conductor 31,

conductor 38, through switch 39 and thence terminating on conductor 2 through conductor 40.

It is evident from the foregoing that in order to close the holding circuit, just described, that switches 3 and 39 must be in a closed condition.

Immediately upon the closure of the foregoing switches 3 and 39, current will begin to flow through the field circuit of the motor and through the armature circuit including the startin resistance 29. Current will also flow through the coil 26 of time delay switch 22 whose contacts are adapted to open in a predetermined time interval after switches 3 and 39 have been closed. Upon the opening of the contacts of the time delay switch .22, a circuit is then established through the coil 36 of contactor 33, which has been shunted out by the time delay switch 22, that actuates thepivotal element 34 of the said vductor 2|, conductor 35, contactor coil 36, conductor 31, coil 26, conductor 38, switch 39, and conductor 40, terminating on the conductor 2. Upon the closure of the immediately described holding circuit, the contactor 33 is closed and establishes it in the circuit through the motor armature 48 which is thence the normal running condition of the motor circuit. Upon the closure of contactor 33, the motor circuit then includes conductor I, the switch 3, conductor 4, the thermo-elements 6 and 8, conductor 9, contactor elements l and I6, conductor 2! connecting to contact 32 and contactor arm 34, thence connecting to conductors 39 and 3| to the motor 48 and terminating on the conductor 2.

In the event that there should be a prolonged overload, but not suflicient to constitute a shortcircuit, the thermo-element 6 will open its circult and establish the field and motor armature circuits through the coil I causing all armature current to flow therethrough. The energizing of coil 1 will cause the holding element I2, of jumper III, which is normally kept in'a closed position by spring l3. to be withdrawn from jumper I0, thereby allowing the spring I I to open the aforementioned holding circuits and deenergize the coil I4a of circuit breaker I4 and the coil 36 of contactor 33 thereby opening contactors l4 and 33. This action'will open both field and armature circuits and allow the motor to come to rest in the usual manner. As soon as the circuit has been opened, the jumper Ill may again be restored to the condition of Fig. 1 to close the contacts between conductors 29 and 5 and permit the reestablishment of that portion of the holding circuit as well as the closure between the thermo-element 6 and its contactor 8. From the foregoing it will be seen that there is a complete load protection on account of overheating, and in the event of a short-circuit, there will be suflicient current passing through the coil 1 to open the holding circuits and thus allow the deenergizing of the several holding circuit coils as previously described,

vFig. 2 sets forth a form of time delay switch employa'ble in the above circuit which constitutes the coil 26 functioning as an exciting coil and the shell or casing element 25 having the separable contacts. The casing element constitutes a metallic conducting shell 42 provided with a closure 43 of a non-conducting material that has an electrode 44 fixed therein. The conductor 24 is secured to electrode 44 and conductor 23 is secured to the casing 42 that is preferably made of a stainless steel. The electrode 44 has an element 46 slidably arranged thereon having a nonconducting portion 45 engaging electrode 44. The element 46 is placed in a mercury bath 41. Upon the energizing of coil 26, there will be a magnetic field established in said coil that will lift the element 46 axially upwardly along the electrode 44 and by reason of the aperture 49 formed in the gear roe base of the element 46, mercury will flow therethrough. The size of aperture 49 will determine the time interval to open switch 22. As soon as Q the mercury has flown through the aperture 49 into the lower end of the casing 25, the circuit between the electrode 44 and 23 will be broken thereby establishing the circuit through the holding coil 36 as previously described. The level of the mercury 41 when 46 is lifted upwardly and after having flown out of 46 will be below the bottom of electrode 44 and the parts must be so proportioned as to accomplish this result.-

Element 46 is normally at the lower end of casing 42. Upon energization of coil 26 it is lifted to the upper end of casing 42 so as to allow the circuit through the mercury 41 to be broken. The coil 26 will hold the part 46 in the elevated position as long as energized. When coil 26 is deenergized 46 will settle to the lower end of 42 allowing mercury 41 to enter 46 through one or more apertures 46a arranged in the wall of element 46; the number and size of said apertures determining the time for the circuit to be reestablished through electrode 44.

The conductor 4| is a grounding conductor that is intended to neutralize the casing of motor 48 and is a more or less conventional expedient.

From the foregoing it is apparent that a motor starting circuit has been provided in which the starting resistance 29 is definitely shunted out of the starting circuit a predetermined interval of time after the closure of the switches 3 and 39. The time interval involved is determined, as stated above, by the length of time that it takes a given quantity of mercury enclosed in the element 46 to flow through the aperture 49 and thereby break-the circuit between the electrode 44 and the casing 42 of the portion 25 of the mercury time delay switch 22. The starting resistance 23 will, therefore, be positively removed from the starting circuit in predetermined time interval and thereafter the stopping 'of the motor on overload, etc. will be determined by the coil 1 or the thermo-element 6 as the case may be and no danger of burning out of the starting resistance will be possible.

It is further apparent that upon closing of switches 3 and 39 that a relatively high voltage will be placed across coil 14a and when contact 44 breaks with the mercury 41 that coil 36 will be placed in series with coil l4a thereby reducing the power consumption and imposing the same voltage across coils 36 and I 411 .in series. The coil l4a upon starting will close'contactor l6 with a hammer like blow to establish a positive contact between the elements l5 and |6a of circuit breaker I4. When a contact such as l6a is employed, there will be a combined rolling and wiping action on contact l5 to clean the contactor elements to further positively assure the best possible conduction of current.

That whichis required as newnovel and useful and whichis' sought to be protected by Letters Patent 0f the United States is as follows:

1. In a motor starter; current supply lines therefor; a motor armature; a motor field; a contactor and a coil therefor; a circuit breaker and a coil therefor; a mercury switch and a coil therefor; a starting resistance; said contactor disposed in parallel to said resistance; means to energize said field from said supply lines; means to connect said circuit breaker, said resistance and said armature in series across said supply lines to start said motor; a shunt circuit to close said circuit breaker which includes connecting said. circuit breaker coil, said mercury switch and its coil across said lines; said mercury switch opening after a predetermined time interval; and a second shunt circuit means to close said contactor to shunt said starting resistance, which includes connecting said contactor coil in series with said circuit breaker coil and mercury switch coil after said mercury switch has opened thereby connecting each of said coils in series across said supply lines.

2. In a motor starting circuit; a field and an armature for said motor; current supply lines ior said armature and field; a starting resistance;

-a contactor adapted tov short-circuit said resistance; a circuit breaker; a timing device comprising a mercury switch and anoperating coil; an electro-magnet for said contactor; an electromagnet for said circuit breaker; means to establish an energizing circuit for connecting said circuit breaker, said armature and resistance across said lines which includes said circuit breaker electro-magnet, said mercury switch and said mercury switch operating coil; means to connect said field across said lines; and means to energize said contactor electro-magnet to short-circuit said resistance upon opening of said mercury switch after a predetermined time to thereby place said contactor electro-magnet in series with said operating coil and said circuit breaker electro-magnet.

3. In an automatic motor starting control; a motor armature; a current supply; a starting resistance; a shunting contactor for said resistance; a circuit breaker; a timing device including a mercury switch and an operating coil; an electro-magnet for said contactor; an electromagnet for said circuit breaker; a series power starting circuit connectible to said current supply for said control which includes said resistance, said circuit breaker and said armature; means to connect a shunt control circuit for said series power circuit to said supply which includes said circuit breaker electro-magnet, said mercury switch and said coil; said circuit breaker coil having a high voltage impressed thereon to close said circuit breaker with a hammer-like blow; means to energize said contactor coil which comprises opening said mercury switch after a predetermined time interval to thereby energize said contactor electro-magnet and short-circuit said resistance; said contactor electro-magnet being then connected in series with said circuit breaker electro-magnet and said coil across said supply.

4. In a motor starter circuit; a current supply; a motor armature; a starting resistance; a circuit breaker and an operating element therefor; a contactor and an operating element therefor;

a timing device'which includes a mercury switch and an operating coil therefor; means to connect a starting circuit which includes said circuit breaker element, said mercury switch and its operating coil to said supply; said circuit breaker closing with a hammer-like blow; a shunt holding circuit for said starting circuit connectible to said supply which includes said resistance, said armature and said circuit breaker; and means to connect said contactor across said resistance and in series with said armature and circuit breaker, which includes connecting said contactor element in series withsaid coil and circuit breaker element after said mercury switch has been opened; said contactor closing upon energization of its element.

5. In a motor starter; a current supply; an electric motor; a starting resistance; a shunting contactor for said resistance including an operating coil; a circuit breaker including an operating coil; a timing switch including an operating coil; means to establish a starting circuit by connecting the armature of said motor, said resistance and said circuit breaker in series to said supply; means to close said starting circuit which includes means to connect said circuit breaker operating coil, said timing switch and its operating coil to said supply; and'means to close said contactor which comprises energizing the coil thereof by connecting it in series with said timing switch operating coil upon the opening of said timing switch.

6. The combination with a motor armature; a starting resistance for said armature; a circuit breaker in series with said resistance and armature; a coil to operate said circuit breaker; a shunting contactor for said starting resistance; a coil to operate said contactor; a timing device including a switch and an operating coil; a shunt circuit for said series circuit including sa'id circuit breaker coil and both elements of said timing device; said timing device opening after a predetermined time and establishing a second shunt circuit including said circuit breaker coil, said contactor coil and said timing device coil; and said contactor shunting said resistance when said timing switch opens thereby energizing said contactor coil and closing said contactor.

7. The combination with a motor armature; a starting resistance for said armature; a contactor for shunting said resistance; a solenoid to operate said contactor; a circuit breaker; a solenold to operate said circuit breaker; said circuit breaker, said resistance and said armature connected in series when said motor is started, a mercury switch; an operating solenoid therefor; a first shunt circuit which includes said circuit breaker solenoid, said mercury switch and its operating solenoid; said mercury switch opening after a predetermined time and establishing a second shunt circuit, which includes said contactor solenoid; said mercury switch solenoid and said circuit breaker solenoid; said contactor closing and shunting said resistance when said mercury switch establishes said second shunt circuit.

8. In an automatic starter for electric motors which comprises; a starting resistance; an accelerating contactor for shunting out said resistance; said contactor includinga shunt operating coil; a timing device including a mercury switch and an operating coil; a circuit breaker; said circuit breaker including a shunt operating coil; a shunt circuit to close said circuit breaker which includes said timing switch; said mercury switch opening after a predetermined time and closing said accelerating contactor which includes establishing a second shunt circuit that includes each of said operating coils, said contactor closing when its operating coil has been energized.

9. The combination with a motor armature; a starting resistance; a shunting contactor; electro-magnetic means to close said contactor; a circuit breaker in series with said armature and resistance; means to close said circuit breaker; a timing device comprising a switch and an operating 0011; a shunt circuit for said series circuit which includes said timing device switch and coil and said means to close said circuit breaker; means to energize said electro-magnetic means to close said shunting contactor which includes opening said timing switch to thereby include said electro-magnetic means in said shunt circuit when said timing device switch is opened,

10. In combination with a motor armature; a starting resistance; a circuit breaker in series therewith; a shunting contactor for said resistance; said circuit breaker including a coil; said contactor including a coil; a timing device including a switch and an operating coil; said resistance and said circuit breaker connected in series with said armature during starting; an energizing shunt circuit for said series circuit; which includes said both timing device elements and said circuit breaker coil; and means to close said shunting contactor'which involves opening said timing switch to thereby remove samefrom said shunt circuit and to include said contactor coil in said shunt circuit; said contactor closing when its coil has been included in said shunt circuit.

11. The combination with a motor armature;

a starting resistance and a circuit breaker in series with said armature; said circuit breaker including an operating coil; a contactor to shunt said resistance after lapse of a predetermined time; a timing device including a switch and a coil; a shunt circuit for said series circuit which includes said timing device elements and said circuit breaker coil; a coil for said contactor; means to close said contactor to thereby shunt out said resistance which includes disconnecting said timing switch from said shunt circuit and including said contactor coil in said shunt circuit; and said timing device switch opening after a predetermined time to energize said contac tor coil.

LILLIAN C. CHANDLER, Administratria: of the Estate of Homer P. Chandler, Deceased.

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