US1392058A - Motor-control system - Google Patents

Description

H. 0. JAMES.

MOTOR CONTROL SYSTEM.

APPLICATION FILED JAN. 8, I919- IQW lJa

INVENTOR Hen/y Ode/hes.

. ATTORNEY entree STATES I HENRiT D. JAMES, 015 EDGEWOOD PARK, PENNSYLVANIA, 'ASSIGNOR TG WESTING- rarest orrice.

HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPQRATION F PENNSYL- VANIK.

MOTOR-CONTROL SYSTEM.

neeaeae.

To all whom it may concern:

Be it known that l, HENRY D. JAMES, a citizen of the United States, and a resident of Edgewood Park, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Motor-Control Systems, of which the following is a specification.

invention relates to motor-control systems and has particular relation to motoraccelerating systems embodying resistorcontrolling contactors, the closing of which is under the control of successively operable relays.

in previously proposed systems of this character, the relay coils are energized by the motor current to automatically maintain the relays open for a predetermined length of time, or so long as the current is above a predetermined value, after every operation of short-circuiting a portion of the accelerating resistor. As the motor current rises from a comparatively low to a comparatively high value afterevery short-circuiting operation, these systems are subject to the disadvantage that the relays may close prematurely, before the motor'current can build up to values sufficiently large to hold them open. '20 make these systems at all practical, it is necessary to-mechanicallv interlock the contactors and the relays and to provide additional means for maintaining the relays open until the current builds up to the required holding values.

An object of my invention is to provide an accelerating system of the above designated character, the relay coils of which shall. bev

. responsive to uniformly decreasing electrical conditions so that the mechanical interlocking means and the additional maintaining means may be dispensed with.

Another object of my invention is to provide such a system which shall be especially adapted for push-button control.

A further object of my invention is to provide a control system for a motor, the acceleration of which shall be determined in accordance with several difi'erent methods Still another object of my invention is to provide a motor-accelerating system which shall be adapted to control also the speed of the motor.

Specification of Letters Patent.

relay coils are made Patented Sept. 27, 1921;

Application filed January 8, 1.919. Serial No. 270,146.

Other objects of my invention will appear hereinafter.

According to the specific forms of my invention herein illustrated and described, the responsive to the drop 1n the voltage across the accelerating resistor, but if an alternating-current motor be employed, they may be energized by the.

The startthough this opening may be before or after the motor cirdrop in voltage across two-phase leads. relays are automatically opened before ing the motor, efiected either cuit is closed,

ccordi'ng to one form of my lnvention, the motor acceleration is controlled both by the voltage drop across the resistor and the counter-electromotive force of the armature. According to another form of my invention, t e control circuits are so arranged as to control not only the initial acceleration of the motor but also its acceleration after speed changes.

In the accompanying drawings, Figure l is adiagrammatic representation of circuits and apparatus for carrying out my invention; Fig. 2 is a similar diagram, the circuits being arranged for control of the motor both in accordance with the drop in voltage across the resistor and the counter-electromotive force of the armature, and Fig. 3 is a diagrammatic view of a system illustrating the application of my invention to an alternating-current motor.

Referring to Fig. 1, a direct-current m0-.

tor, the armature of which is shown at l and the shunt field-magnet winding at 2, is connected between line conductors 3 and 4, separated by a line contactor 5, with a regulating resistor 6 normally in series with the armature l. The contactor is adapted to be closed by an energizing coil 8. One or more contactors 10, ll and 12 (three are illustrated) control the shunting of successive portions 13, 14c and 15 of the regulating resistor 6 through the medium of energizing coils 19, and 21, the circuits of which are controlled by normally closed relays 25, 26 and 27 having energizing coils 22 22 and 22, respectively, connected in parallel (F ig. l or in series (Fig. 2) across the regulating resistor 6. The relay is adapted to close auxiliary contact members 60 when occupying its open position. Switches 51 and 61 or simultaneously therewith.-

are mechanically connected to the contactor so as to be opened and closed simultaneously with the opening and the closing of the contactor. The control circuits are adapted to be energized by a start push button and to be denergized by a stop push button.

Upon closing the start pushbutton, a circuit is established from the line conductor 4, through the stop-and-start push buttons, a conductor 28, the coils 22, 22 and 22 and the armature 1, to the line conductor 3. This circuit is of high resistance, the resistance being embodied in the coils 22, 22 and 22, or an additional resistormay be employed. The current which passes through this circuit will, therefore, not be of sufficient strength to have any appreciable effect upon the motor armature 1, but the relays 25, 26 and 27 will be immediately opened. The opening of the relay 25 causes the closing of a circuit which extends from the line conductor 1, through the stop-andstart push buttons, the conductor 28, and the contact members 60 and the coil 8, by way of a conductor 30, to the line conductor 3. The consequent energization of the coil 8 causes the closing of the line contacto'r 5 and the mechanicallyuconnected switches 51 and 61. The cont-actor 5 establishes the motor circuit. The switch 61 creates a holding circuit for the coil 8 through the stop push button. The coil 8 will thus remain energized to maintain the contactor 5 and the switches 51 and 61 closed, even though contact be broken at 60. The switch 51 creates a holding circuit for the coils 22, 22 and 22 in shunt to the start button so that this button may be released, the circuit. of the coils 22, 22 and 22 bein made from the line conductor 4, through tie stop push but ton, the switch 51, the conductor 28, the relay coils and the armature 1, to the line conductor 3.

Upon the establishing of the motor circuit, the coils 22, 22 and 22 wil be energized in accordance with the drop in voltage across the resistor 6. As'the motor begins to accelerate, and the current flowing through the motor to decrease, in conseuence, the voltage across the resistor will ecrease and, assuming the relays 25, 26 and 27 to be properly, des1gned,-as by making them of difierent weights or by causing them to be actuated by springs of different strengths or by properl designing the number of turns in the coi s 22, 22 and 22,-'- so as to cause these relays to close in succession in accordance with different values of the voltage across the resistor 6, the relay 25 will close first, establishing a circuit extending from the line conductor 4, throu h the contactor 5, a conductor 29, the relay 5 and the coil 19, by way of a-conductor 30, to the line conductor 3. 4 The consequent energizetion of my system mes es tion of the coil 19 causes the contactor 10 to close and the resistor portion 13 to be ShOI'tr. circuited. In similar fashion, the relays 26 and 27 will close later, in accordance with the successively lowered values of the voltage across the resistor 6, and the coils 20 and 21 will become energized to cause the closing of the contactors 11 and 12 and the consequent short-circuiting of the portions 14 and 15 of the resistor 6. The armature 1 will then be connected directly across the line.

A study of the system just described will make clear that it is impossible to start the motor unless the resistor 6 is initially in circuit with the armature 1, thereby reventing injury to the motor which would result if the armature 1 were initially connected directly to the line conductors 3 and 4:. This result is made possible b the fact that the line contactor 5 cannot close'the motor circuit until the relays 25, 26 and 27 have reviously been opened to prevent the closing of the contactors 10, 11 an d,12 by their energizing coils 19, 20 and 2,1, and the consequent short-circuiting of the resistor 6. It is only when the relay 25 occupies its open position, to close the contact members 60, that the coil 8 can be energized to cause the closing of the contactor 5.

it is not, however; essential to the operathat the relays 25, 26 and 27 be 0 ened before the contactor' 5 is closed. 11 Fig. 2, I- have illustrated a system in which the contactor 5 ma be closed before, or simultaneously with, t e opening of the relays, but, of course, the motor is not permitted to start until the relays 25, 26 and 27 have first been opened. In the system of Fig. 2, 1 illustrate an additional feature of control which may, if desired, be embodied also in the system of Fig. 1.

The arrangement of circuits is similar to that of Fig. 1, except that the coils 19, 20 and 21 are each connected, at one end, to the connecting points of the successive resistor portions 13, 14 and 15, and, at the other ends, by way of the conductor 30, to the other side of the armature 1. The coils 19, 20 and 21 are therefore responsive to the counter-electromotive force of the armature.

Upon the actuation of the start push button, a circuit is established which extends from the line conductor 1, through the two push buttons and dividin rent passes through the coils 22, 22 and 22, the resistor 59 and he armature 1, and the other part passes through the coil. 8, by way of the conductor 30, the two branches of the circuit terminating in the line conductor 3. The relays 25, 26 and 27 are immediately 0 ened and the contactor 5 is immediately 0 osed. It is not necessary, however, that the relays be immediately opened, because,

, part of the curshown. The switch motive force of length of time, they cannot eflect the operation of the motor, since the coils 19, 20 and 21 cannot actuate the contactors 10, 11 and 12 until the counter-electromotive force of the motor builds up to a sufficiently high value. It is safer, however, tohave the relays and the contactor 5 operate together, as 61 establishes holding circuits for the coil 8 and the relay coils, but the switch 51, in this case, controls the circuits of the coils 19, 20 and 21 across the armatur terminals.

- The relays 25, 26 and 27 are arranged to be successively closed in accordance with the value of the fallin voltage drop across the resistor 6. Upon t e closing of the relay 25, a circuit is established from one side of the armature 1, "by way of the conductor 30, through the switch 51, to the other terminal of th armature 1. Similarly, upon the closing of the relays 26 and 27, the coils 20 and 21 will be energized by the counter-electrothe motor, the circuit of the coil 20 including the resistor portion 15.

When this counter-electromotive force, therefore, becomes .great enough to energize the coils 19, 20 and 21 sufi iciently to cause the closing of the contactors 10, 11 and 12, the resistor portions 13, 1e and 15 will be successively short-circuited.

In the illustrated embodiment of this invention, the coils l9 and 20 are shown as controlled not only in accordance with the counter-electromotive force of the motor, but also in accordance with the resistance through the resistor portions 14, and 15, respectively. If desired, of course, the circults may be so arranged as to close the contactors 10, 11 and 12 in reverse order so as to short-circuit the resistor portions 15, 14

and 13, in the order named, in which event 11 and 10 will be succesthe contactors 12,

' in accordance with the sively controlled counter-electromotive force of the motor only..

The acceleration of the system of Fig. 2 '5 thus controlled in accordance with two different methods of control. First, the relays 25, 26 and 27 are successively'closed in accordance with the drop in potential across the resistor 6; secondly, it is immaterial when these relays are closed if the counter-electromotive force of the motor has not previously built up to values sufiiciently large to control the contactors 10, 11 and 12. If this counter-electromotive force builds up too rapidly, the closing of the contactors must await the closing of the relays in accordance with the voltage drop across the resistor. If this voltage drops too rapidly, the closing of the contactors must await the building up of the counter electromotive force. As shown, moreover, the action of the coils 19 and 20 is delayed by the resistor portions 14 and 15.

I have shown the coilsf22, 22 and 22, in

they may both Figs. 1 and 2, as connected across the entire resistor 6. It will be connected across a smaller port on or across different portions of this resistor.

into two resistor portions .13, 13, 141-, 14 and 15, 15, respectively, which are adapted to be controlled by and 71, having energizing coils 19, 20, 21, 72 and '73, respectively. The contactors are respectively controlled by relays 25, 26, 27, 68 and 69, having energizing coils 22 22*, 22, 22 and 22 which are connected, in series or in parallel, in series with a resistor 59 of high resistance, across two of the phase leads of the secondary winding 66. lit is, of course, possible, as illustrated in Fig. 7 of No. 236,937, filed May 27, .1918, to connect these relay coils directly across the terminals of-the resistor, as in Figs. 1 and 2, but 1 preferably connect these coils as shown because they will thus, as in the case ofthe other connection, be subjected to a falling voltage and because, by means of this con nection, it is possible not only to control the acceleration of the motor but also its speed. This is because a high-resistance coil, connected across two of the leads of the secondary winding of an alternatingcurrent motor, yields a decreasing magnetic field as the motor speed increases. The con tactor coils 19, 20, 21, 72 and 73 are connected, respectively, in circuit with the relays and the master switch 7, by conductors the primary leads. A

78 and 79, to two of slow-acting relay 80, having an actuating coil 81 in the circuit of one of the second ary leads, is connected in the circuit of the conductor 79 for an obvious purpose.

The operation is as operation of the master switch 7 to its first operatire position, the coil 8 is energized to cause the closing or" the contactor 5, thereby to connect the primar winding 65 to the source of energy. he motor is thereupon energized, but current cannot yet flow through the contactor coils, by way of the conductors 78 and 79, even though the master switch 7 be immediately actuated to be obvious that of a master contactors l0, 11, 12,

my copending application, Serial succeeding positions, because the relay 80 is open. Current is induced in the secondary winding 66 and traverses the resistor 6.

' The relay coils are energized, causing the opening of the relays. After a time, the slow-acting relay 80 is closed by the coil 81 so that, when the relay) 25 is first closed, upon the voltage drop etween the secondary a circuit is established, assuming the master switch 7 .to occupy its second position, from one of the primary leads, by the conductor 78, through the relay 25 the coil 19, the master switch 7, the conductor 79 and the slow-acting relay 80, to a second of the primaryleads. The contactor 10 is thereupon closed by its coil 19 to short-circuit the resistor portion 13. Upon the voltage difference between the secondarg leads alling to a second and lower pre etermined value, the relay 26 will become closed to cause the closing of the circuit of the coil 20, when the master switch 7 is moved to its third position. The consequent closing of the contactor 11 results in placing the resistor portions 14 and 15 in parallel to each other and in series with the resistor portion 13, thus again reducing the resistances of the several circuits of the secondary phase windings. Upon the relay 27 later closing, the contactor 12 will become closed to shortcircuit the resistor portions 13, 1 1 and 15. Similarly, the closing of the relay 68 will cause the closing of the contactor 70 to place the resistor portions 14: and 15 in parallel and, ultimately, the closing will cause the closing of to short-circuit the 15. The resistor the contactor 71 resistor portions 14 and 6 will now be entirely short-circuited. The slow-acting relayl remains closed until after all the relays ave closedf lnthis system, too, it is necessary that the resistor 6 be traversed by current before the starting of the motor; for, unless this is so, the coil 81 will and the above-described operations can not take place.

It will be noted that an additional advantage accruing from the connection 0 the relay coils across two of the secondary leads is that it renders possible the employment of an unbalanced secondary resistor.

A further advantage is the following: the relays may be made to open and to close at a difference in voltage of from 10 to 15 per cent. By suitably manipulating the master switch 7 the circuits of the contactor coils may be opened for purposes of speed control. Upon the consequent reinsertion of resistance into the secondary circuit of the motor, the motor speed will-decrease, thereby causing'several or all of the relay coils to reactuate their relays to their open positions, which relays will again close, in

leads falling to a predetermined value,

that my invention of the relay 69' 0 opening said not be suiiiciently. energized,-

source 0 energy for said ling said short-circu'r jting. switches,

accordance with speed conditions, upon the master switch 7 being again actuated to close the circuits of the contactor coils. The danger of suddenly throwing the motor directly across the line, without protective resistance, is thus avoided.

I have illustrated but three of the many forms which my invention may take and have suggested a few others. It is obvious is not limited to the specific embodiments therefore, that my claims be construed broadly, except in so far as limitations may be specifically set forth therein.

1 claim as my invention:

1. The combination with an electric motor having a resistor associated therewith, a switch for controlling said resistor and a normally closed relay for controlling said resistor-controlling switch, of a coil energized in accordance with the voltage across said resistor for controlling said relay.

2. The combination with an electric motor having a resistor associated therewith, a switch for controlling. said resistor and a normally closed relay for controlling said resistor-controlling ed to be subjected to a decreasing voltage for controlling said relay and means for opening said relay .preliminarily to shortcircuiting said resistor.

3. The combination with an electric motor having a resistor associated therewith, a plurality of switches for short-circuiting said resistor and a normally closed relay for controlling each of said short-circuits ing switches, said relays being adapted to be successively closed in accordance with predetermined conditions, of means for relays before starting said motor.

4. The combination with an electric moto;- having a resistor associated therewith, a source of energy for said motor, a switch for SllOlt-OlI'CllltlIig said resistor and a relay ;tor controlling said switch, of a coil energized in accordance with the voltage across said resistor for controllin said relay and means for connecting said coil to said source before starting said motor.

5. The combination with anelectric motor havin motor, a plu- -circuitin said regressive y acays for controlrality of switches'ior shor resistor and a plurality of t'iated, normally closed re ing an energizing toil, of means for connecting said coils to said source before startin said motor, and means for thereafter su jecting said coils to the voltage drop of said resistor.

6. The combination with an electric motor having a resistor associated therewith, of a switch controlled in accordance with the shown and I desire,

switch, of a coil adapta resistor associated therewith, a

each havvalue of the counter electromotive force troinotive force of said motor for contro1- 10 of said Inotor for controlling said resistor,

ling said resistor and a swltch controlled and a switch controlled 1n accordance with by the voltage of said resistor for controlthe electrical conditions of said motor for lin said counter-electromotive-force switch. controlling said counter-electromotive-force fn testimony whereof I have hereunto switch. subscribed my namethis 24th day of Dec, 15

7. The combination with an electric mo- 1918. tor having a-resistor associated therewith,

of a switch controlled by the counter-elec- HENRY D. JAMES.

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