US2310050A - Motor control system - Google Patents

Description

Feb. 2, 1943. o. AUSTIN 2,310,050

MOTOR CONTROL .S YSTEM Filed on. so, 1941 152 g3 g 2 e6 m U 3 M 0 INVENTOR 0560070546770.

1 3 "3 B 9 61/1,: 0.157999 50/) 0.1g M z i ATTO EY Patented Feb. 2, 1943 MOTOR CONTROL SYSTEM Bascum 0. Austin, Forest Hills, Pa

assignor to Westinghouse Electric 4; Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 30, 1941, Serial No. 417,158 10 Claims. (Cl. 172-179) My invention relates, generally, to motor control systems and, more particularly, to systems for controlling the operation of the propelling motors of electric vehicles, such as trolley cars and coaches.

In order to prevent discomfort to the passengers on electric vehicles it is necessary that the vehicles decelerate smoothly as well as accelerate smoothly. Modern equipment has been devised which provides relatively smooth acceleration oi electrically propelled vehicles and one object of my invention is to provide smooth deceleration, both when power is shut off during motoring and when the braking action is discontinued during dynamic braking.

Another object of my invention is to enable an electric vehicle, such as a trolley coach, to be started under severe ioad conditions Without having too much speed once the coach is started.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with my invention, a cushioned shut-off of power is obtained by causing the same devices used during automatic acceleration to function in the reverse order to insert resistance in the motor circuit in steps which will so soften the loss of tractive efiort that it will not be uncomfortable to the passengers. Likewise, a cushioned shut-off of theelectric brake is obtained in a manner similar to the power shut-cit. The first few steps of acceleration may be taken independently of the current limit relay and without actuating the controller to its last position, thereby obtaining sufiicient power to start the vehicle under heavy loads without having too much speed after it is started.

For a fuller understanding of the nature and objects of my invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing in which:

Figure 1 is a diagrammatic view of a control system embodying my invention, and

Fig. 2 is a chart showing the sequence of operation of the control switches shown in Fig. 1.

Referring to the drawing, the system shown there n comprises a motor M having an armature wind ng l and a series field winding I l, switches LS, MI a d RI for connecting the motor across power conductors I 2 and I3 which are energized from trolley conductors l4 and I5 through cur rent collectors l6 and I1, respectively, and additional switches B and Fl for establishing dynamic braking connections for the motor. The switch Fl is also utilized for shunting the field winding ll of the motor during a portion or the accelerating period and an additional switch F2 is also provided for field shunting purposes. The motor M is of a series type suitable for propelling a trolley bus or other electric vehicle (not shown).

In order to control the motor current during the accelerating and dynamic braking periods of operation, a resistor R is connected in the motor circuit. A plurality of resistor shunting switches R2, R3, R4, R5, R6, R1 and R8 are provided for shunting the resistor R from the motor circuit step-by-step during both acceleration and dynamic braking. The switch RI is also utilized for resistor shunting purposes.

As shown in the drawing, the switches Rl to R3, inclusive, F! and F2 are each provided with a closing coil for actuating the switch to the closed position and a holding coil for retaining the switch in the closed position after it has been closed by the closing coil. The sequence of operation of the resistor shunting switches controlled by interlock progression in a manner well known in the art.

Under normal operating conditions the operation of the resistor shunting switches is auto matically controlled by a curl-chi; iimit relay LR which is responsive to the motor current. In order to permit the vehicle to be started under severe load, conditions, contact members it are provided on an accelerating controller A6 and. connected in parallel-circuit relation to contact members ii? on the limit relay Mt. The contact members it are closed during the first three operating positions or" the controller AC, thereby permitting the switches Rl to Rt, inclusive, as indicated by the sequence chart in Fig. 2, to be closed independently of the operation of the limit relay LR. In this manner a sufllcient amount of resistance may be shunted from the motor circuit to permit it to start a heavy load without having too much speed once the vehicle is started, as was the case in former control systems of the present type.

A braking controller BC is provided for controlling the dynamic braking operation. As indicated in the chart in Fig. 2, the resistor shunting switches are operated in the same sequence during dynamic braking as during acceleration. The operation of the resistor shunting switches during dynamic braking is normally under the control of the limit relay LR.

In order to provide for a cushioned shut-oft of power during acceleration of the vehicle and also for a cushioned shut-oi! of the electric brake during dynamic braking, thereby avoiding discomfort to the passengers or the vehicle by the sudden loss of tractive eflort or of the braking eil'ect, the controller AC is provided with contact members 2| to 24 connected in parallel-circuit relation to contact members 25 to 28, respectively, on the controller BC which cooperate with the interlocks on the resistor shunting switches to cause these switches to be operated in a sequence during power and brake shut-offs which is the reverse of the sequence of operation of the switches during accelerating and braking, as will be described more fully hereinafter. With a view to permitting the reclosing of certain of the resistor shunting switches to secure the reverse sequence oi operation, the controller BC is provided with contact members 29 which are closed during the first three operating positions of the controller to parallel the contact members IQ of the relay LR through an interlock 30 on the switch R1. Thus, if the controller BC is returned to one of its first three positions during dynamic braking, the proper sequence of operation of the switches for gradually inserting resistances into the motor circuit to secure an easy shut-off of the braking efiect is obtained independently. of the operation of the limit relay LR.

In order that the functioning of the foregoing apparatus may be more clearly understood, the operation of the system will now be described in more detail. If it is desired to accelerate the vehicle in a normal manner under the control of the limit relay, the accelerating controller AC may be immediately actuated to its last operating position, thereby causing the switches LS, RI

and MI to be closed to connect the motor across the power conductors and the switches R2 to R8, inclusive, to be closed in the sequence indicated in the sequence chart to shunt the resistor R from the motor circuit. As explained hereinbefore, the sequence of operation of the switches is controlled by interlocks provided on the switches and the switches are normally closed in a step-by-step manner under the control of the limit relay, thereby limiting the current supplied to the motor. Thus, it is impossible for the next step in the progression to be taken until the motor current is reduced to a value permitting the limit relay to close its contact members to complete the energizing circuit for the next switch in the progression. The foregoing automatic control of the operation of a plurality of resistor shunting switches is well known in the art and it is believed to be unnecessary to describe it in detail in the present specification,

If it is desired to increase the motor current beyond the amount normally permitted by the limit relay LR, thereby increasing the power delivered by the motor to enable it to start the vehicle under a heavy load, the controller AC may be actuated to any one of the first three positions depending upon the amount of current it is desired to supply the motor. In this manner a predetermined number of resistor shunting switches may be closed independently of the operation of the limit relay LR without increasing the vehicle speed an undesirable amount after the vehicle is once started. When the vehicle is started, the controller may then be actuated to the desired operating position, thereby permitting the progression of the switches to continue in the norm-a1 manner under the control of the limit relay.

Assuming that the controller AC is actuated to position three, the switches LS, R and MI are closed to connect the motor across the power con- -ductors I2 and I3 in series-circuit relation with the resistor R and the switches' R2 to R1, in-

clusive, are then closed by interlock progression to shunt portions of the resistor R from the motor circuit step-by-step independently oi the operation of the relay LR. The energizing circuit for the switch LS may be traced Irom the positive conductor I2 through contact members 3| on the controller AC, conductor 32, contact members 33 on the controller BC, conductor 34, an interlock 35 on the switch B, conductor 33 and the actuating coil of the switch L8 to the negative con ductor- I3. The energizing circuit for the switch MI extends from the conductor 36 through the actuating coil of the switch MI to the negative conductor I3. Following the closing of the switch LS the energizing circuit for the switch RI is established from the conductor 34 through an interlock 31 on the switch LS, conductor 38, an interlock 39 on the switch It], conductor 4|, the closing coil of the switch RI, conductor 42 and the contact members iii of the controller AC to the negative conductor I3.

Upon the closing of the switch RI, an energizing circuit for the switch R2 is established from the conductor 4| through an interlock 43 on the switch RI, conductor 44, the closing coil of the switch R2, conductor 42 and the contact members l8 of the controller AC to the negative conductor I3.

It will be noted that the holding coil for each one of the resistor shunting switches is energized upon the closing of the switch. Thus, the holding coil for the switch RI is energized through. an interlock 45 carried by the switch RI and the holding coil for the switch R2 is energized through an interlock 66 carried by the switch R2. Likewise, the holding coils for the remaining resistor shunting switches and the field shunting switches FI and F2 are energized through interlocks carried by the respective switches.

Following the closing of the switch R2, the closing coil of ,switch R3 is energized through a circuit which extends from the conductor 44 through an interlock 41 on the switch R2, conductor 58, the closing coil of the switch R3, conductor 32 and the contact members E8 of the controller AC to the negative conductor I3. The energizing circuit for the switch R4 is then established from conductor 64 through an interlock 89 on the switch R3, conductor 5! the closing coil of the switch R4, conductor 32 and the contact members it of the controller AC to the negative conductor i3.

Since it has been assumed that the controller AC is on position three, an energizing circuit for the switch R5 is next established from conductor 44 through contact members 24 of the controller AC, conductor 52, an interlock 53 on the switch R4, conductor 54, the'closing coil of the switch R5, conductor 82 and the contact members I8 of the controller AC to the negative conductor I3.

Likewise, an energizing circuit for the switch R6 is established upon the closing of the switch R5. This circuit may be traced from the conductor 38, through contact member 22 of the controller AC, conductor 55, an interlock 56 on the switch R5, conductor 51, the closing coil of the switch R5, conductor 42 and the contact through a circuit which extends from the conductor 38, through an interlock 58 on the switch R8, conductor 59, the closing coil of the switch Rl, conductor 42 and the contact member I8 of the contrcler AC tov the negative conductor l3.

Since it has been assumed that the controller AC is on position three the progression of the resistor shunting switches is stopped at this time. As explained hereinbeiore, the controller AC may be actuated to any one of the remaining positions four, five or six, depending upon the accelerating rate desired, after the vehicle is started. The progression of operation of the remaining resistor shunting switches is now placed under the control of the limit relay, which functions in the normal manner to limit the current supplied to the motor as the vehicle accelerates.

Assuming that the controller AC is actuated to position six, the switches RI to R8 are opened, as indicated in the sequence chart in Fig. 2, and the switch R8 is then closed to connect two portions of the resistor R in the motor circuit in parallel-circuit relation. The energizing circuit for the closing coil of .the switch R8 may be traced from conductor 38 through contact members 23 of the controller AC, conductor 8|, an interlock 62 on the switch R2, conductor 83, the closing coil of the switch R8, conductor 64, the interlock 30 on the switch R1, conductor 42, and the contact members IQ of the relay LR to the negative conductor l3.

Following the closing of the switch R8, the switches R2 to R6, inclusive, are reclosed as indicated in the sequence chart. The energizing circuit for the closing coil of the switch R2 extends from the conductor 38 through an interlock 65 on the switch R8, conductor 44, the closing coil of the switch R2, conductor 42 and the contact members iii of the relay LR to the negative conductor l3. The closing coils of the switches R3, R4, R5 and R8 are energized by interlock progression through circuits previously traced.

Following the closing of the switch R8, the

switch RI is reclosed to complete the shunting of the resistor R from the motor circuit. The energizing circuit for the closing coil of the switch Ri extends from the conductor 38 through the interlock on the switch R8, conductor 44, an interlock 68 on the switch R6, conductor 4|, the closing coil of the switch RI, conductor 42 and the contact members IQ of the relay LR to the negative conductor I3.

Upon the closing of the switch RI, the field shunting switch Fl is closed to shunt the field winding ll of the motor M through a resistor 51 and a reactor 68. The energizing circuit for the switch Fl may be traced from the conductor 5I through an'interlock 88 on the switch R4, which is closed at this time, conductor I I, contact members 72 on the controller BC, conductor I3, contact members I4 on the controller AC, conductor 35, an interlock 16 on the switch RI, conductor ii, an interlock I8 on the switch R8, conductor '59, the closing coil of the switch Fl, conductor -l2, and the contact member IQ of the relay LR to the negative conductor l3.

Following the closing of the switch Fl, the switch F2 is closed to short the resistor 61 from the field shunting circuit, thereby shunting the field winding ll through only the reactor 88 which causes the motor to operate at its maximum speed in a manner well known in the art.

The energizing circuit for the closing coil of 'the switch F2 extends from the conductor 48 through an interlock 8| on the switch Fl, conductor 82, the closing coil of the switch F2, conductor 42 and the contact members of the relay LR to the negative conductor l3. The closing of the switch F2 completes the accelerating cycle for the motor.

If it is desired to remove power gradually from the motor during the accelerating period in order to avoid discomfort to the passengers of the vehicle, the controller AC may be gradually returned towards the 0115 position. If the controller is returned toward the off position the contact members on the controller and the interlocking members on the resistor shunting switches cause the switches to be operated in the reverse sequence from that taking place during acceleration of the motor. The reverse operation of the switches causes the resistor R to be gradually inserted in the motor circuit to decrease the motor current. If the controller is stopped on any intermediate position, the sequence of operation of the switches is stopped accordingly, as indicated in the sequence chart in Fig. 2. Thus ii. the controller is stopped on position three, the parallel connection for the resistor is removed and a portion of the resistor is connected in the motor circuit in series-circuit relation. By returning the controller to position two, the switches R8 and R1 are opened to insert more of the resistor in the motor circuit. When the controller is returned to position one, the switch R5 is opened to insert still more resistance in the motor circuit. If it is desired to disconnect the motor from the power circuit completely, the controller AC may be actuated to the off position.

If it is desired to decelerate the vehicle by dynamic braking, it is necessary to return the accelerating controller to the off position which causes the closing of the switches B, Fl and Rl to establish a dynamic braking circuit for the motor. The energizing circuit for the switch B may be traced from the positive conductor l2 through contact members 83 on the controller AC, conductor 19, an interlock 84 on the switch LS, which is in the open position at this time, conductor 85 and the actuating coil ofswitch B to the negative conductor I3. The energizing circuit for the switch *Fl extends from the conductor 19 through the closing coil of the switch Fl, conductor 42 and the contact members l9 of 1 the relay LR to the negative conductor l3. Following the closing of the switch B, the closing coil of the switch RI is energized through a circuit which extends from the conductor 13 through an interlock 88 on the switch B, conductor 38, the interlock 39 on the switch R'I, conductor 4|, the closing coil of switch Rl, conductor 42 and the contact members IQ of the relay LR to the negative conductor l3.

By actuating the braking controller BC to any one of the braking positions, depending upon the braking rate desired, the resistor shunting switches may be closed under the control of the limit relay LR in accordance with the position to which the controller is actuated, as indicated in the sequence chart in Fig. 2. If the controller is actuated to position five to obtain the maximum braking rate the switches run through their complete sequence of operation in the same order and in the same manner as described hereinbefore for the acceleration of the vehicle. The operation of the switches is under the control of the limit relay, thereby limiting the braking current permitted to circulate through the motor.

In this manner the resistor R is gradually insert-.

ed in the braking circuit to gradually decrease the braking current and hence the braking efiect.

As explained hereinbefore, the contact members 25, 26, 21 and 28 on the braking controller BC are connected in parallel-circuit relation to the contact members 2|, 22, 23 and 24, respectively, of the controller AC, which contact members function in cooperation with the interlocks on the resistor shunting switches to cause the reverse sequence of operation of the switches if the braking controller is returned toward the "01? position. Since it is necessary for certain of the switches to be reclosed in order to maintain the proper sequence of operation during the braking shut-cit and there is a possibilitythat the limit relay LR would operate to prevent the reclosal of these switches at the desired time,

the contact members 29 on the braking controller bypass the contact members I! of the limit relay,

LR as explained hereinbefore to permit the reclosing of these switches independently of the operation of the relay. In this manner smooth deceleration of the vehicle at all times is assured.

From the foregoing description, it is apparent that I have devised an automatic control system which provides for manual control of the first few steps of power independently of the current limit relay which normally controls the automatic operation of the system, thereby permitting sufllcient power to be applied to the motor of a vehicle to start it under heavy load conditions without so interfering with the normal operastep-by-step, a relay responsive to the motor current for controlling the operation of said switches, and means actuated by said controller for causing the operation of a predetermined numberof said switches independently-of said relay. 7

3. In a motor control system, in combination, a motor, a power conductor, switching means for connecting the motor to the power conductor, a controller for controlling the operation of said switching means, a resistor for controlling the 7 motor current, a plurality of switches for shunt-- ing saidresistor step-by-step, a relay responsive to the motor current for controlling the operation of said switches, and means actuated by said controller for causing the operation of a predetermined number of said switches independently of said relay, and interlocking means on said switches for determining their sequence of operation.

4. In a motor control system, in combination, a motor, switching means for connecting the motor to a power source, a controller for controlling the operation of said switching means, control means for controlling the motor current, a relay responsive to the motor current for normally controlling the operation of said control means, and means actuated by said controller for controlling the operation of said control means independently of said relay.

5. In a motor control system, in combination, a motor, a power conductor, switching means for connecting the motor to the power conductor,

a controller for controlling the operation of said tion of the system that an excessive amount of speed is obtained once the vehicle is started.

Furthermore, the present system provides for a cushioned shut-off of power and electric brake by making the same devices used with automatic acceleration function in the reverse order to insert resistance in the motor circuit in steps during both the power and brake shut-offs to soften the loss of tractive efiort or the loss of braking efiect, thereby assuring both smooth acceleration and deceleration of the vehicle.

Since many modifications may be made in the apparatus and arrangement of parts without departing from the spirit of my invention, I do not wish to be limited other than by .the scope of the appended claims.

I claim as my invention:

1. In a motor control system, in combination, a motor, switching means for connecting the motor to a source of power, a controller for controlling the operation of said switching means, a resistor for controlling the motor current, a plurality of switches for shunting said resistor stepby-step, a relay responsive to the motor current for controlling the operation of said switches, and means on said controller for causing the operation of a predetermined number of said switches independently of said relay.

2. In a motor control system, in combination, a motor, switching means for connecting the motor to a power source, a controller for controlling the operation of said switching means,

a resistor for controlling the motor current, a'

plurality of switches for shunting said resistor switching means, control means for controlling the motor current, a relay responsive to the motor current for normally controlling the operation of said control means, and means on said controller for operating said control means independently of said relay under abnormal conditions.

6. In a motor control system, in combination, a motor, a power conductor, switching means for connecting the motor to the power conductor, an accelerating controller for controlling the operation of said switching means, additional switching means for establishing dynamic braking connections for the motor, a braking controller for controlling the operation of said additional switching means, a resistor for controlling the motor current during acceleration and dynamic braking, a plurality of switches for shunting said resistor step-by-step, interlocking means on said switches, contact members on said controllers cooperating with said interlocking means to operate said switches in a predetermined sequence during acceleration and dynamic braking and in the reverse se'quence during power and brake shut-ofis, a relay responsive to the motor current for normally controlling the operation of said switches, and means actuated by said controllers for controlling the operation of said switches independently of said relay.

7. In a motor control system, in combination, a motor, a power conductor, switching means for connecting the motor to the power conductor, an accelerating controller for controlling the operation of said switching means, additional switching means for establishing dynamic braking connections for the motor, a braking controller for controlling the operation of said additional switching means, a resistor for controlling the motor current during acceleration and dynamic braking, a plurality of switches for shunting said resistor step-by-step, interlocking means on said switches, contact members on said controllers cooperating with said interlocking means to operate said switches in the same sequence during acceleration and dynamic braking and in the reverse sequence to shut off power from the motor and to release dynamic braking, a relay responsive to the motor current for normally controlling the operation of said switches, and means actuated by said controllers for controlling the operation of said switches independently of said relay.

8. In a motor control system, in combination, a motor, a power conductor, switching means for connecting the motor to the power conductor, an accelerating controller for controlling the operation of said switching means, additional switching means for establishing dynamic braking connections for the motor, a braking controller for controlling the operation of said additional switching means, a resistor for controlling the motor current during acceleration and dynamic braking, a plurality of switches for shunting said resistor step-by-step, interlocking means on said switches, contact members on said controllers cooperating with said interlocking means to operate said switches in a predetermined sequence during acceleration and dynamic braking and in the reverse sequence during power and brake shut-offs, said contact members being connected in parallel-circuit relation, 9, relay responsive to the motor current for normally controlling the operation of said switches, and means actuated by said braking controller for controlling the operation of said switches independently of said relay during the release of dynamic braking.

9. In a motor control system, in combination, a motor, a power conductor, switching means for connecting the motor to the power conductor, an accelerating controller for controlling the operation of said switching means, additional switching means for establishing dynamic braking connections for the motor, a braking controller for controlling the operation of said additional switching means, a resistor for controlling the motor current during acceleration and dynamic braking, a plurality of switches for shunting said resistor step-by-step, interlocking meanson said switches, contact members on said controllers cooperating with said interlocking means to operate said switches in the same sequence during acceleration and dynamic braking and in the reverse sequence to shut off power from the motor and to release dynamic braking, said contact members being connected in parallel-circult relation, a relay responsive to the motor current for normally controlling the operation of said switches, and means actuated by said braking controller for controlling the operation of said switches independently of said relay during the release of dynamic braking.

10. In a motor control system, in combination, a motor, switching means for establishing dynamic braking connections for the motor, a. controller for controlling the operation of said switching means, a resistor for controlling the motor current during dynamic braking, a plurality of switches for shunting said resistor stepby-step, interlocking means on said switches c0- operating with said controller to operate said switches in a predetermined sequence to brake the motor dynamically and in the reverse sequence to release dynamic braking, a relay responsive to the motor current for controlling the operation of said switches during dynamic braking of the motor, and means on said controller for controlling the operation of said switches independently of said relay during the release of dynamic braking.

BASCUM O. AUSTIN.

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