US1924306A - Control apparatus - Google Patents

Description

Aug. 29, 1933.

w. G. cooK ET'AL 1,924,306

CONTROL APPARATUS Filed' nay zo, 1950 A'TTORNEY Patented Aug@ 29, '1933 UNITED s'rA'rss CONTROL APPARATUS Willard G. (look, Forest Hills, and Henry D.

`laines, Edgewood, Pa., assignors to Westinghouse Electric and Manufacturing Company. a Corporation of Pennsylvania Application May 2li, 1930. Serial No. 453,884

v claims. (ci. riz-17e) Our invention relates to control apparatus and more particularly to control systems for reversing such mototrs as are used to drive rolling-mill tables or similar reciprocating devices.

One object of our invention is to provide for controlling the time of reversal of a reversing motor.

More'speciiic objects of our invention are, to provide for limiting the current flowing through a motor, at the instant of the reversal of the connections while the motor is rotating in a given dlrection, i. e., during plugging, to a value which the motor will safely stand and to provide for controlling the period of reversal of the motor during plugging as a. function of the load. f

A further object ci our invention is to provide a system of control for reversing a motor that shall be, simple and eilicient in operation, comparatively inexpensive and easy oiumanufacture, in view oi the relatively few parts required, and which may be readily applied to a motor. v

The novelfeatures that we consider characteristic of our invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specic embodiment, when read in connection with the accompanying drawing, in which:

Figure 1 shows, diagrammatically, a control system for reversing motors wherein the time of reversal is determined by the inertia of the load and wherein aplugging relay of a simple type is shown.

Fig. 2 is a side elevational view of 'a modiiication oi the plugging relay illustrated in Fig. 1.

Referring more particularly to Fig. 1 o! the drawing, 1 and 2 designate the positive and negative line conductors o! the source of'power, and M represents the motor for operating the reciprocating device. The directional contactors are designated by the reference characters 23 and 24; and R designates a starting resistor having resistor sections 30, 31 and :i2-which are controlled by a plurality oi' accelerating relays 11, 12 and l13 which are, in turn, controlledby a pair of time limit relays 6 andl. The entire control system is controlled by a manual controller 10. The plugging relay P controls .the accelerating relay 11 and, in consequence, the shunting of the resistor section 32.

Assuming that the line conductors 1 and 2 are not energized, then the various elements of the controis'ystemwillstandinthepositionshownin v"a, thereby establishing a circuit from the en- Fig. 1. Ii the switch (not shown) in lines 1 an`d 2 be closed and the controller 10be in the oil position, an energized circuit is established from the positive line conductor 1 through 'conductors 3 and 4, resistor 4", neutralizing coil 6 of the tixne- 60 limit relay 6, neutralizing coil '7' of the time-limit relay 7 and conductor 8, to the negative line cond uctor 2.

When the controller 1'0 is moved to the first Iorward position, a circuit is established from the positive line conductor 1, through conductor 3, contact lingers 64 and 67 bridged by the connected controller segments 9 and -9' conductor 14, actuating coil 15 of the directional contactor 23, conductors 16 and 17, actuating coil 18 of the 70 line contactor 5 and conductor 19,' to the negative line conductor 2. Energization ot the directional contactor 23 and the line contactor 5 causes the closure of the contact members associated with the directional contactor 23 and line contactor 5. 75

The' actuation oi contactors 5 and 23 to their closed positions causes the establishment of the motor circuit from the positive line conductor 1, through the upper contact members of the directional contactor 23,' conductor 25, armature 30 26, conductors 2'? and 28, lower contact members of the directional contactor 23, series eld 29, resistor segments 30, 31 and 32 of the resistor R, conductor 33, the contact members of the line contactor 5 and conductor 19, to the negative line conductor 2. Connected across the armature terminals, is a circuit through conductor 34, coil 35 o! the plugging relay P and conductor 36.

Since the resistor R is in series with the motor circuit, the resistance drop across vresistor sections 31 and 32 causes immediate operation .of the time-limit relays 6 and 7 to open the contact members associated with each time-limit relay. Time-limit relays 6 and 'I are designed to have a negligible time constant when coils 44 and 41, respectively, are energized. However, upon deenergization of coils 44 and 41, a definite time elapses before the respective contact members associated with. these time-limit relays close.v

When the manual controller 10 is actuated to the rst iorwardposition, a circuit is established which extends from the energized conductor 14, through conductor 20, operating coil 21 ofthe plugging relay P and conductor 22, to the negative line conductor 2. Upon energization of the operating coil 21, the amature 4810i the plugging relay moves in a counter-clockwise direction about its pivot point to engage a contact member los ergized conductor 20, through-the conductor 37 on the armature 43, conductor 33, the actuating 'coil of the accelerating relay ll and conductor 39,

to the negative line conductor 2. Since the circuit for the directional contactor 23 and line con- 5 tactor 5, and the circuit for the operating coil 21 of the plugging relay l? are in parallel, a very small interval of time elapses after the motor` circuit is established, before relay 11 operates to' close the contact members associated with this relay to shunt the resistor section 32. Resistor` section 32, while, in some measure and for a very short interval of time, operating as a section of the starting resistor, does not function as a starting resistor. The resistor section 32 has` rather high resistance value and serves to prevent excessive current from owing through the motor windings during plugging operations as will be pointed -out more in detail hereinafter.

shunting of the resistor section 32 by the relay .v position establishes a circuit from the positive line conductor 1, through conductor 3, Contact ngers 64 and 65 bridged by the controller segment 9 conductor 45, the contact members of' time-limit relay 7, conductor 46, accelerating relay 12 and conductor 39, to the negative line conductor 2. Operation of the accelerating relay 12 removesthe resistance drop across the magnetizing coil 44 and, in consequence, time-limit relay 6 is deenergized. After a predetermined interval of time, the contact members of time-limit relay 6 close to establish a circuit for the accelerating relay 13 extending from the energized conductor 45, through the contact members of the timelimit relay 6, conductor 47, accelerating relay 13 and conductor 39, to the negative line conductor 2. The closure of the accelerating relay 13 causes the shunting of the last resistor section 30, and the motor comes up to full speed in the forward direction.

Assuming that it isA desired to plug the motor while it is running at full-forward speed, the con-f troller 10 is mov'ed to the full-reverse position, and the directional contactor 24 is energized to thereby close the contact members associated with this directional contactor, the line contactor 5 being also energized by the movement of the controller to close its contact members. Because of the inertia of the load and the rotating armature, rotation of the armature will continue in the same direction. During the movement of the controller from the full-forward to the full-reverse position, directional contactor 23 and the actuating coils of the accelerating relays 11, 12 and 13 are d eenergized, and all the sections of the resistorR are connected in series with the motor.

It is very desirable that the resistance in series with the motor during plugging be quite high to prevent `excessive currents from passing through the armature which might injure the motor. 'I'he .plugging relay P accomplishes this desirable result. It will be noted that, when the directional cdntactor 24 closes, during the plugging operation, the voltage impressed upon the coil 35 accesos is still in the same direction and, in consequence,

the closed-circuit condition at point a is maintained until the resistance drop across the armature overbalances the counter-electromotive force. When this takes place, the voltage impressed on the armature terminal, being reversed, causes energization of coil 35 in. a direction opposite to its previous energization. A circuit is thuswestab- .lished which extends from the positive line conductor 1, through conductor 3, contact fingers 64 and Sii-bridged `by the controller segment- 9 conductor 60, the closed contact point b, conductor 37 on`the armature 48, conductor 38, the re'- lay 11 and conductor 39, to the negative line conductor 2. Since the energization of coil 35 is a function of the inertia of the load on the motor, the circuit for the relay 11 will remain open at point buntil the motor speed has substantially decreased to zero i. e., relayll cannot operate to shunt the resistor section 32 before the motor comes substantially to rest. Resistor section 32, having a relatively high ohmic value, thus remains connected in the armature circuit during decelerationof the motor, thereby preventing excessive currents through the armature during the plugging operation.

It is understood, of course, that, if it be desired to start initially in the reverse direction, the controller 10 is moved in the reverse direction from the first to the second reverse position, and the sequence of operation and the circuits thus established for the motor and the various elements of the control system, are similar to the sequence of operation of the circuits above described in connection with the controller move` ment in the forward direction.y

In Fig. 2 is shown a modified type of plugging relay P provided with a pair of operating coils 35 and.35", which may be connected across thel armature terminals of the motor. The function of this type of plugging relay is similar to the relay shown in Fig. 1. In some applications, the plugging relay shown in Fig. 2 gives better service because of the fact that two coils are employed. During themovement ofthe controller 10 in a forward direction, the operating coil 21' is energized 'and voltage is impressed across the amature terminals. The magnetic effect of the coils 21' and 35'` and 35"'is additive.

tion, coils 35' and 35" act in opposition to the magnetic eect ofv coil 50. When the motor has come substantially to rest, the magnetic effectof coils 35'` and 35" becomes negligible, and the operating coil 50 causes the closing of the contacts at b'. v

'I'he functioning of plugging relay P' is, therefore, similar to the functioning of the plugging relay P where the magnetic effect of operating coils 21 and 35 is-additive when the voltage impressed across these coils is in the same direction. Further, the magnetic effect of coils 35 and 50 is additive when the voltage impressed across them is in the same direction. In short, the magneti(` effect of coil 35 is always dierential with reference to operating coils 21 and 50 during plugging operation, regardless of the direction of rotation of the motor at the instant of plugging.

Since, during the plugging operation, the manual controller 10 need not be moved to the fullias opposite position, the plugging'v operation may f take place subject to both manual and automatic u Leccese control but, in no case, may the plugging operation take place at a more rapid rate than is den termined by the inertia of the load and the ro,a tating armature and the time constant for which the time-limit relays 6 and 'l have been adjusted.

We do not wish to be restricted to the specific structural detalls, arrangement of parts or circuit connections herein set forth, as various modifications thereof may be eected without dew parting from the spirit and scope ci our invention. We desire, therefore, that only such limitations shall be imposed as are indicated in the appended claims.

We claim as our invention:

i. In a control system for a reversing motor, including e. source of power, a motor, directional contactors and a manually operable controller for controlling the contaotors, in combination, s. plugging resistor, shunting means for the plugging resistor, a relay for controlling the shunting means including a coil for operating the relay upon movement of the vmanual controller in one direction, a coil i'or operating the relay upon movement of the manual controller in the opposite direction, and a coil connected across the armature ,terminals of the motor for controlling the operation or the relay oy said com.

2. In a control system for a reversingv motor, including a source of power, a motor, directional contactors and a manually operable controller for controlling tlie contactors, in combination, a plugging resistor, a sliunting circuit for tile plm,- ging resistor, a relay for controlling tnesnuntinc circuit including a coilfor operating the relay upon movement of the manual controller in one direction, a coil for operating the relay upon movement ci the manual controller in the opposite direction, and a plurality ci coils connested across the armature terminals oi the motor for controlling the operation oi. saidV relay oy said coils. l

3. In a control'system for a reversing motor, including a source of power, a motor, directional contactors and a. manually operable controller for controlling the contactors, in combination, a plugging resistor, starting resistors, shunting means for each of said resistors, a relay for controlling the shunting 'means iol; the plugging resistor, said relay including a coil for operating the relay upon movement of the manual controller in one direction, a coil for operating the relay upon movement of the manual controller in the opposite direction and a coil connected across the armature terminals ci the motor for controlling the operation of the relay by said coils,

and time limit relays disposed to operate predetermined intervals oi' time after the operation o! the shunting means for the plugging'resistor to control the shunting means of the respective starting resistors.

4. In a control system for a reversing motor,

.including a source of power, a motor. directional contactors and a manually operable controller lor controlling the contactors, in combination, a starting resistors, shunting means for each of said resistors, a relay for controlling the shunting means for the plugging resistor, said relay including a coil for operating the relay upon movement of the manual controller in one direction, a coil for operating the relay upon movement of the manual controller in the opposite direction and a coll connected across the armature terminals oi the motor :for controlling the operation of the relay by said coils, time limit relays disposed to operate predetermined intervals or time after the operation or tice shunting means for the plugging resistor to control the shunting means of vthe respective starting resistors, and circuit means interconnected with said manual controller to control 'the energlzation o! said time limit relays' to effect the operation ci said shunting means for the starting resistor at any time alter the operation of the snunting means lor the pluggirm resistor.

5. In a control system for a reversing motor, including e. source of power, a reversing motor, directional contactors and a manually operable controller for controlling the contactere, in combination, a plugging resistor, starting resistors, shouting means for each ci said resistors, a relay for controlling tlie shunting means or the plugging resistor, said relay including a coil for operating the relay upon movement of the manual' controller in one direction, a coil :lor operating the relay upon movement of the manual controller in the opposite direction and a plurality oicoils connected across tlie armature terminals or the motor -for controlling tlie operation oi said relay by said coils, and time limit relays disposed to operate predetermined intervals ici time after the operation of 'the sl'luntina" means for the plugging resistor to control the sliunting means of the respective starting resistors. i

6. ln a control system for a reversing motor, including a source oi newer, a reversing motor. directional contaotors and a manually operable m@ controller for controlling the contactcrs, in combinatlon, a plugging resistor, starting resistors, sliunting means for each oi said resistors, a relay for controlling the sliunting means for the plugging resistor, said relay including a coil or operating the relay upon movement of the manual controller in one direction. a coil for operating the relay upon movement oi the manual controller in tlie opposite direction and a plurality o1 coils conn nested across the armature terminals of the motor for controllingr the operation of said relay by said coils, time limit relays disposed to operate predetermined intervalso time alter the operation .of the shunting means for the plugging resistor to ycontrol the shunting means of the respective starting resistors and` circuit means interconnected .4 with said manual controller to control the energization of said time limit relays to eect the operation of -said shuntinc means for the starting resistor at any time after the operation of the shunting means for the plugging resistor.

'7'. In an'electric control system for reversing motors, in combination, a source of power, a motor, directional, contactors, a manually operable controller for selectively energizing the contactors, a plugging resistor, a single plugging relay controlling the effective resistance o! the plugging resistor, circuit connections for selectively enerizlns the relay substantially directly to operate in a given direction when the motorie connected for forward rotation and to operate in another given direction when the motor operates in reverse. dlrectiomand circuit connections for controlling the relay responsive, to the counter-clectromotive lll) force ci the motor. M5

l G. COOK.

l mY D. JAMES. v

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