US2214020A - Motor controller - Google Patents

Description

p 0.- 9 P. a. HARWOOD E! m. 2,214,020

I MOTOR CONTROLLER File V- 18, 1939 2 Sheets-Sheet 1 Sepi. w, 1 4 P. s. HARWOOD El AL MOTOR CONTROLLER 2 Sheets-Sheet 2 Filed Nov. 18, 1939 3/ a). MMM

Patented Sept. 10, 1940 UNITED STATES PATENT OFFICE MOTOR CONTROLLER of Delaware Application November 18, 1939, Serial No. 305,098

9 Claims.

This invention relates to motor control systems, and while not limited thereto is particularly applicable to systems of control for motor driven. machine tools such "as wire drawing machines of the multiple unit type.

Wire drawing machines of the multiple unit type are usually provided with a plurality of reducing dies each of which has a pulling drum associated therewith. The several drums are driven by a single motor and the wire is wrapped around said drums for successive drawing through the reducing dies.

In preparing such machines for a drawing operation the operator threads the wire through the first reducing die and then operates the motor for a short period to effect winding of a' few turns of the wire upon the first pulling drum. The wire is then threaded through the second reducing die and the motor is again operated for a short period to effect winding of a few turns of the wire upon the second pulling drum. This process is repeated until the wire is successively threaded through all of the reducing dies and wound upon their associated pulling drums. During these operations it is necessary to operate the motor at a relatively low speed, and in practice it has been found that a period of approximately 4 seconds must be allowed for each of the winding operations.

It has heretofore been proposed to control wire drawing machines of the multiple unit type by means of a time limit controller including a plurality of accelerating switches which operate to shunt a starting resistance for the driving motor in steps separated by given time intervals. However, such controllers have been found objectionable for the following reason. During preparation of the machine for a drawing operation the .load on the driving motor is increased each time the wire is threaded through a die and wound upon the pulling drum associated therewith. The accelerating switches of a controller of the aforesaid type may be set to operate successively at 4 seconds intervals so that regardless of vary ing load conditions the motor will operate at a relatively low speed for the required interval during each of the winding operations. However, when the wire is to be wound upon the second drum or'possibly the third drum the driving motor may not have sufficient torque to start until after the first accelerating contactor closes.

It is, therefore, necessary for the operator to wait at least 4 seconds before the winding operation is started, and if suificient torque is not developed for starting until the second accelerating contactor closes it is necessary to wait 8 seconds. Obviously such periods of delay before the motor is started are undesirable, and the present invention has among its objects to provide an improved controller which overcomes this objection.

Another object is to provide an accelerating controller for motor driven machines of the aforesaid type which operates at an extremely rapid accelerating rate until the motor starts and thereafter operates at a reduced accelerating rate to bring the motor up torunning speed.

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate an embodiment of the invention which will now be described, it being understood that variousmodifications may be made in the embodiment illustrated without departing from the spirit and scope of the appended claims.

In the drawings,

Figure 1 is a straight line diagrammatic representation of a control system embodying the invention, and

Fig. 2 is a key illustration of the switches and relays embodied in Fig. 1.

The illustration of the switches and relays in Fig. 2 shows them with their coils and contact members disposed in horizontal alignment with their positions in the straight line circuits of Fig. 1 s6 that the reader may readily determine the position of the coil and contact members of any switch or relay in the straight line circuit. The reference characters also serve as a guide to the relation between the, operating coils of the switches and relays and their associated contacts. For example in switch IM the operating coil IM operates contacts [M IM and IM The switches and relays are named as follows:

IM M IA 2A 3A 4A 5A IVR 2VR 3VR AS Armature shunt switch DB Dynamic braking switch FA Field accelerating switch CT Timing relay UV Undervoltage relay Referring to Fig. 1, the same illustrates a direct }Main switches Accelerating switches Voltage relays current motor M to be supplied with current from a direct current supply circuit indicated by lines L L The motor shown is provided with an armature A, a series field winding F and a shunt field winding F The control means for motor M includes a pair of electromagnetically operated main switches IM and 2M for connecting armature A, and series field winding F across lines L L in series with a plurality of starting resistance sections R to R inclusive. The control means for said motor also includes a plurality of electromagnetically operated accelerating switches IA to 5A for successively shunting resistance sections R to R a field accelerating switch FA for controlling accelerating resistance sections R and 1'1. in the shunt. field circuit of said motor, and a dynamic braking switch DB for connecting a dynamic braking resistance R in shunt with armature A. I The main switches IM and 2M and also the accelerating switches IA to 5A; inclusive, are of a conventional type, said main switches each having an operating winding M and said accelerating switches each having an operating winding A and a holding winding A The operating windings of main switches IM and 2M and also the operating windings of accelerating switches 'IA to 5Aare controlled by a master switch MS having stationary contacts I, 2, 3 and 4 and cooperating movable contacts l 2, 3 and 4 Response of the accelerating switches IA, 2A, and 3A is timed by capacitors C C and C respectively, and also by voltage relays IVR, 2VR and 3VR, respectively. Capacitor C and a resistance r are connected in parallel with the holding coil IA of accelerating switch IA; capacitor C and a resistance r are connected in parallel with the holding coil 2A of accelerating switch 2A, and capacitor C and a resistance r are connected in parallel with the holding coil 3A of accelerating switch 3A. Voltage relay IVR is provided with a set of normally closed contacts IVR. for connecting a resistance 1 in shunt with the holding coil IA? of accelerating switch IA; voltage relay ZVR is provided with a setof normally closed contacts ZVZR, for connecting a resistance r in parallel with the holding coil-2A of accelerating switch 2A, and voltage relay 3VR is provided with normally closed contacts 3VR for connecting a resistance r in parallel with the holding coil 3A of accelerating switch 3A. The operating windings IVR 2VR and 3VR of said voltage relays are connected in parallel with each other and with a resistance section R and the armature shunt switch AS provides for connection of said winding and said resistance across the terminals of armature A.

Accelerating switches 4A and 5A are rendered operative upon response of the dynamic braking switch DB. Relay CT controls the dynamic braking switch DB and the armature shunt switch AS and said relay is provided with timing control means including a capacitor C which is connected across the terminals of operating winding GT through the medium of a resistance r". Field accelerating switch FA is controlled by accelerating switch 5A and operation thereof is timed by a capacitor C which is connected across the terminals of operating winding FA through the medium of a resistance T The controller also includes stop push buttons 5 and 6 which are connected in series in the energizing circuit of undervoltage relay UV and as hereinafter set forth said relay when deenergized necessitates return of master switch MS to I The operation of the aforedescribed controller and the circuit connections thereof will now be more fully described.

With voltage on lines L L and master switch MS in ofi position, under voltage relay UV is energized by a circuit extending from line L through contacts I, I 2 and 2 of master switch MS through the operating winding UV of said relay and through stop push buttons 5 and 6 to line 1?. Upon response of the under voltage relay UV the contacts UV thereof shunt master switch MS to. establish a maintaining circuit for the operating winding UV of said relay.

Also with voltage on lines L L the holding windings associated with accelerating switches IA to 5A and the operating windings associated with field accelerating switch FA and timing relay CT are energized as follows. Holding winding IA of accelerating switch IA is energized through the medium of contacts IM of main switch IM and the capacitor C associated therewith is charged through the medium of resistance 1' Holding winding 2A of accelerating switch 2A is energized through the medium of contacts IA of accelerating switch IA and the of resistance 1 Holding windings 4A and 5A of accelerating switches 4A and 5A are connected in series and are energized through the medium of a resistance 1 Operating winding FA of field accelerating switch FA is energized through the medium of contacts 5A of accelerating switch 5A and the capacitor C associated therewith is charged through the medium of resistance 1 Operating winding CT of timing relay CT is energized through the medium of contacts 3A of accelerating switch 3A and the capacitor C as,- sociated therewith is charged through the medium of resistance 1'".

Upon energization of field accelerating switch FA contacts FA and FA close, and upon closure capacitor C associated therewith is charged of contacts FA resistance sections R" and R are shunted to provide for connection of shunt field switch AS and the contacts CT thereof open to prevent energization of the dynamic braking switch DB.

To effect starting of the motor, master switch MS is moved into its on position. The operating windings IM and 2M of main switches IM and 2M are then energized by a circuit extending from line L through contacts UW of under voltage relay U.V through contacts 2, 2 3 and 3 of said master switch, through the operating windings of said main switches and through contacts UV of said under voltage relay to line L. Upon response of main switches 'IM and 2M armature A and series field windings F are connected across lines L L through the medium of resistance sections R to R inclusive. Also the shunt field winding F is connected directly across lines L L by contacts FA of field accelerating switch FA and resistance section R is connected across the contacts DB immediately upon response of main switches IM andZM the operating windings IA 2A and 3A of accelerating switches IA, 2A and 3A are energized by a circuit extending from line L through contacts UV of under voltage relay UV through contacts 2, 2 4 and i of the master switch MS to and through said operating windings and through contacts IM and iM of said main switches to line L However, accelerating switches IA, 2A and 3A do not respond immediately due to the action of their associated holding windings A 'Also upon response of main switches IM and 2M the operating winding AS of armature shunt switch AS is connectedacross lines L L through the medium of contacts IM and 2M of said main switches. The armature shunt switch AS thus responds immediately upon closure of main switches IM and 2M and the contacts AS thereof connect resistance r and the operating windings IVR 2VR and SVR of the voltage relays across the terminals of armature A to render said voltage relays responsive to given counter-voltage values in the motor circuit.-

Upon response of main switch IM the contacts lM thereof interrupt the energizing circuit for the holding winding IA of accelerating switch IA. Assuming that the motor starts upon closure of main switches IM and 2M the countervoltage in the motor circuit effects response of relay IVR and upon response of said relay the contacts lVR thereof interrupt the shunt circuit around the holding winding IA including resistance 1 Holding winding 4A is thus subjected to the discharge of capacitor C and after a predetermined prolonged period of delay the voltage in said winding is reduced to a value topermit response of accelerating switch EA under the action of its operating winding HA However, assuming that the load on the motor is such that the same fails to start immediately after closure of main switches HM and 2M voltage relay iV'R remains in circuit closing position to provide for discharge of the energy in holding winding HA and capaci- 'tor C in a relatively short interval through resistance R The holding effect of winding Al is thus quickly reduced to permit operation of accelerating switch lA under the action of its operating winding IA after a relatively short interval upon closure of main switches EM and 2M. Response of accelerating switch IA excludes resistance section R from the armature circuit of the motor.

Upon response of accelerating switch IA the contacts IA thereof interrupt the energizing circuit for the holding winding 2A of accelerating switch 2A, and assuming'that the motor starts upon exclusion of resistance section B the counter-voltage in the motor circuit effects response of voltage relay ZVR. Holding winding 2A is then subjected to the discharge of capacitor C and after a prolonged period of delay the voltage in said holding winding is reduced to a value to permit operation of accelerating switch 2A under the action of its operating winding 2A However, if the load on the motor is such that the same fails to start upon exclusion of resistance section R voltage relay ZVR remains in circuit closing position to provide for discharge of the energy in holding winding 2A and capacitor C in a relatively short interval through resistance R Thus if the motor fails to start upon response of accelerating switch IA, accelerating switch 2A responds after a relatively short interval under the action of its operating winding 2A and the contacts 2A thereof shunt resistance section R Immediately upon response of accelerating switch 2A the contacts 2A interrupt the energizing circuit for the holding winding 3A of accelerating switch 3A. Assuming that the motor starts upon exclusion of resistance section R the counter-voltage in the motor circuit effects response of voltage relay 3VR. Holding winding 3A is then subjected to the discharge of capacitor C and after a prolonged period of delay the voltage in said holding winding is reduced to a value to permit response of accelerating switch 3A. under the action of its operating winding 3A If the load on the motor is such that the same fails to start upon exclusion of resistance section R voltage relay 3VR remains in closed position to provide for discharge of the energy in holding winding 3A and capacitor C in a relatively short interval through resistance 7 Thus if the motor fails to start upon response of accelerating switch 2A, accelerating switch 3A responds after a relatively short interval under the action of its operating winding 3A 'and the contacts 3A thereof shunt resistance section R Upon response of accelerating switch 3A the contacts 3A thereof open to disconnect the operating winding CT of timing switch CT from lines L L Operating winding GT is then subjected to the discharge of capacitor C and after a predetermined interval the voltage of said winding is reduced to a value to permit opening of said timing relay. Upon opening of timing relay CT the contacts CT thereof close prior to contacts CT and shunt the operating winding AS of armature shunt switch AS. Contacts A5 are thus opened to deenergize the operating windings Ill/R ".iVR and 3VR of the voltage relays and to exclude resistance R. Also upon dropping out of timing relay CT the contacts GT thereof connect the operating winding DB of dynamic braking switch DB across lines U, L through the medium of contacts 5M and 2M of the main switches IM and 2M.

Dynamic braking switch DB then responds to open its contacts DB and close its contacts DB and DB Contacts DB in opening interrupt the shunt circuit around armature A including resistance R Contacts DB in closing establish an energizing circuit for the operating windings of accelerating switches 5A and 5A, said energizing circuit extending from line L through contacts U'V of relay UV through contacts 2, 2 4 and 4 of master switch MS to and through the operating windings 4A and 5A of said accelerating switches and through contacts iM and 2M of the main switches to line L Contacts DB in closing shunt the holding winding 4A of accelerating switch 4A to permit response of said switch under the action of its operating winding 4A Thus upon response of accelerating switch 4A, resistances R R and R are excluded from the motor circuit to effect a further step-of acceleration of the motor.

Upon response of accelerating switch 4A the contacts 4A thereof shunt the holding winding 5A to provide for response of accelerating switch 5A under the action of its operating winding 5A Upon response of accelerating switch 5A the contacts 5A thereof shunt accelerating resistance section 1 Also upon response of accelcrating switch 5A the contacts 5A thereof interrupt the energizing circuit for field accelerating switch FA, and the operating winding PA! of said switch is then subjected to the discharge of capacitor C to delay opening of said switch.

Aftera predeterminedinterval contacts FA open to connect resistances R and R in parallel in the energizing circuit of shunt field winding F and thereafter contacts FA open to exclude resistance section R' from said circuit. Accelerating switch FA thus operates after a predetermined period of delay upon response of accelerating switch 5A to provide two steps of acceleration by weakening of the shunt field winding F The motor may be stopped at any time during acceleration or after the same is brought up to full running speed by momentary depression of either of the push buttons 5 or 6. Depression of either of said push buttons interrupts the afore-. described maintaining circuit for the operating winding UV of under voltage relay UV and said relay then drops out to open its associated contacts UV and UV Upon opening of these contacts the energizing circuits for operating coils of main switches lM and 2M, accelerating switches IA to 5A and dynamic braking switch DB are all interrupted for return of said switches to normal position. Field accelerating switch FA is then energized through the medium of contacts 5A of accelerating switch 5A to provide for exclusion of resistance sections R and R. in the energizing circuit of shunt field winding F and resistance section R is connected across the terminals of armature A by contacts DB of the dynamic braking switch DE. The -motor is thus dynamically braked to effect quick stopping thereof. As is apparent, upon dropping out of under voltage relay UV the master switch MS must be returned to off position as a prerequisite to restarting of the motor.

In connection with the foregoing it should be noted that the above described controller is particularly adapted for use in connection with motor driven-wire drawing machines and meets requirements hereinbefore discussed. In other words, resistances R and R are proportioned to effect starting of the driving motor under all load conditions, and upon starting of the motor the controller insures slow speed operation thereof for 'a sufficient time to efiect the winding operations hereinbefore discussed. I

What we claim as new and desire to secure by Letters Patent is:

1. In a motor controller, in combination, a plurality of starting resistances in the motor circuit, aplurality'of electromagnetic accelerating switches each for shunting one of said resistassociated with said former means for timing the operation of said switches to effect exclusion of said resistances from the motor circuit at a rapid rate until the ,motor starts and to thereafter efiect exclusion of resistances remaining in the motor circuit at a reduced rate Q to bring the motor up to running speed. I 3

2. In a motor controller, in combination, a plurality of starting resistances in the motor cir-' cuit, a plurality of electromagnetic accelerating switches'each for shunting one of said resistances,

each of said switches having an operating winding and a holding winding associated therewith, means for controlling said windings to provide for operation of said switches in a given sequence, and means associated with said holding windings for timing the operation of said switches to provide for exclusion of said resistances from the motor circuit at a rapid rate until the motor starts and to thereafter eifect exclusion of resistances remaining in the motorcircuit at a reduced 1 rate to bring the motor'up to running speed.

3. In a motor controller, in combination, a

plurality of electromagnetic accelerating switches each having a capacitor associated therewith for delaying operation thereof, control means for effecting operation of said accelerating switches in a given sequence subject to delay by said capacitors, and means for modifying the delaying effect of said capacitors upon given electrical conditions in the motor circuit.

4. In amotor controller, in combination, a plurality of electromagnetic accelerating switches each having a capacitor associated therewith for 4 delaying operation thereof, control means for effecting operation of said acceleratingswitches in a given sequence subject to delay by said capacitors and means subjected to control by the counter-voltage in the motor circuit for modifying the delaying efiect of said capacitors.

5. In a motor controller, in combination, a

plurality of electromagnetic accelerating switches each having a capacitor associated therewith for delaying operation thereof, control means for ef- ,fecting operation of said accelerataing switches windings, means acting upon establishment of power connections for the motor to energize said operating windings and to successively interrupt the energizing circuits of .said holding'windings for successive operation of said switches, a capacitor associated with each of said holding windings and coacting therewith upon interruption of its associated energizing circuit to delay operation of its associated switch, and means subjected tov control by the counter-voltage, of the motor for modifyingthe delaying efiect of said capacitors. I

7. In a motor controller, in combination, a plurality of electromagneticaccelerating switches each having a device associated therewith for delaying operation thereof, control means for effecting operationof said accelerating switches in a ,given sequence subject to delay by their associated delaying devices, and means associated with at least the first switch of said sequence for normally reducing the delaying eflect of its associated delaying device, said latter means being rendered ineffective upon starting of the motor.

8.'In a inotor controller, in combination; a

plurality of electromagnetic accelerating switches u each having a device associated therewith for delaying operation thereof for a predetermined interval, control means for efiecting operation of 'sai d accelerating switches in a given sequence plurality of starting resistances in the motor cir:

W for successive operation of said switches, a device associated with each of said holding windings and coacting therewith upon interruption of associated energizing circuit to delay operation of its associated switch, means associated in L certain of said devices for normally reducing the '5 delaying efiect'thereof, said latter means being rendered inefiective upon starting of the inoton PAISLEY B. HARl/VOQD. I JOE-m M, NEWBEAN. ll

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