US2057909A - Motor controller - Google Patents

Description

Oct 20, 1936s 1 J. MfNEWMAN 2,057,909

- MOTOR CONTROLLER I Filed May 18, 19:55 7 '2 Sheets-Sheet 1 nevansz 5109 men 31$ 13 a FORWARD mcu ronwano RUN QMWM V paw '5. swmrwm Oct. 20, 1936. Y J W AN 2,057,909

- MOTOR CONTROLLER Filed May 18, 1955 2 Sheets-Sheet 2 Wm WM- '5. 5\wmww QNW km WXM Patented Oct. 20, 1936 PATENT OFFICE MOTOR CONTROLLER John M. Newman, Milwaukee, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application May is, 1935, Serial No. 22,158

7 Claims.

This invention relates to motor controllers, and

is particularly applicable to controllers for motor driven metal drawing machines.

Metal drawing machines are'usually provided with a motor driven drawing mechanism, and as is well known such machines require speed adjustment of the drawing mechanism to suit the material being drawn and also require stopping of the drawing mechanism or slowdown thereof to a relative low speed when the material breaks or leaves the die.

It has been proposed to provide machines of the aforesaid character with control means including a load responsive relay for effecting automatic slowdown or stopping of the drawing mechanism when the material breaks or leaves the die. However, as heretofore arranged such control means was found objectionable in that it was difficult,

The present invention has among its objects to provide an improved controller for machines of the aforesaid character which overcomes the 30 aforementioned objections.

Another object is to provide a controller for motor driven metal drawing machines having improved load responsive control means associated therewith which provides for automatic slowdown or stopping of the driving motor of the drawing mechanism when the material being drawn breaks or leaves the die and which insures such operation regardless of the speed at which the material is being drawn.

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

The accompanying drawings diagrammatically illustrate two embodiments of the invention which will now be described, it being understood that the embodiments illustrated are susceptible of modification without departing from the spirit and scope of the appended claims.

In the drawings,

Figure 1 diagrammatically illustrates a con? troller for wire drawing machines embodying the invention, and

Fig. 2 diagrammatically illustrates a controller for draw benches which also embodies the invention.

Referring to Fig. l, the same illustrates a reversible motor M for driving the drum or reel of a wire drawing machine, said motor being provided with an armature A, a series field winding F, a stabilizing field winding F and a shunt field winding F A plurality of steps of starting resistance R R 'and R are connected in the armature circuit of said motor and a speed regulating rheostat H3 is connected in the shunt field circuit thereof. Also a step of dynamic braking resistance R is provided to be connected in a closed loop with armature A during stopping of the motor.

The armature circuit of motor M is controlled by two sets of normally open electromagnetic direction contactors -l l--l2 and l3 and normally open accelerating switches -46 provide for exclusion of resistance steps R 1R. while a normally open accelerating switch I! provides for exclusion of series field F and resistance step R Also a normally closed electromagnetic switch I8 is provided for connecting the dynamic braking resistance R across the terminals of armature A and a normally open electromagnetic accelerating switch l9 having a series operatingwinding a and a shunt operating winding!) is provided for shunting the speed regulating rheostat l0.

The direction contactors H--l2 provide for operation'of motor M in its forward or drawing direction while the direction contactors l3-I4 provide for operation thereof in a reverse direction. Said contactors are provided with manual control means including a normally open forward run push button 20, a normally open forward inch push button 2 l, a normally open reverse inch push button 22 and a normally closed stop push button 23. The two sets of contactors lll2 and 13-44 are also controlled by normally closed auxiliary contacts I8 associated with the dynamic braking switch l8 and by contacts 24 of an electromagnetic relay 24 which is responsive to current in the dynamic braking circuit of the motor. For purposes hereinafter set forth contactors H and M are each provided with a bridging contact b and cooperating stationary contacts 0 and d for shunting contacts l8 of the dynamic braking switch l8 and contacts 24 of relay 24.

The control means for contactors l l-l2 also includes an electromagnetic relay 25 which is under the control of the forward run push button 20 and provides for establishment of a maintaining circuit for said contactors through the medium of stop push button 23, auxiliary contacts I 2 associated with contactor l2 and a normally open load responsive relay 2E. Said braking circuit for the motor.

load responsive relay is provided with a series operating winding 28' connected in the armature circuit of motor M and a shunt operating winding 28 which is regulated as hereinafter set. forth by an adjustable rheostat 28 having its adjusting arm mechanically connected to the adjusting arm of speed regulating rheostat ID.

The accelerating switches l5, l6 and H are provided with suitable electromagnetic control means for effecting progressive closure thereof upon establishment of power connections for the motor by either set of contactors il-|2 or l3-l4. The control means for said accelerating switches is not shown since the same may be of any well known type.

The dynamic braking switch 13 is controlled by an auxiliary contactie associated with each of the direction contactors ii and i4, and the shunt operating winding l9 associated with accelerating relay is is controlled by an auxiliary contact 1 associated with each of said contactors. The shunt coil I9 is'also controlled by normally closed contacts, 25 associated with relay 25, normally closed contacts II associated with accelerating switch l1 and normally open contacts 24 associated with relay 24.

The function and operation of the aforedescribed controller and also the circuit connections therefor will now be more fully described,

The material to be drawn is connected to the drum or reel of the wire drawing machine. Motor M is then started in its forward direction, to draw the material through the die, by depression of the forward run push button 20. Upon depression of push button 20 the forward contactors ll-I2 respond, the same being energized by a circuit extending from line L through stop button 23, through push button 20, by conductor III to and through the operating windings II "and H 01' said contactors, by conductors 3l-42 to and through contacts 18* of the dynamic braking switch I8, through contacts 24 of relay 2 and by conductor 33 to line D. The armature of motor M is then energized by a circuit extending from line L through coil, I9 of accelerating switch l9, through contactor I i, through armature A, through contactor I2, through the field windings F and F, through resistances R 1'1. and R and through the series operating winding 23' of load relay 26 to line L.

Immediately upon response of contactor i I the operating winding l8 of the dynamic braking switch III is connected across lines L L by conductor 33 and auxiliary contacts e and d of said contactor and said dynamic braking switch thus responds to interrupt the dynamic Also upon response of contactor H the shunt operating winding I! of accelerating switch I! is connected across iines'L L through the medium of auxilimy contacts I'lassociated with accelerating switch ll, auxiliary contacts I and d of contactor II and conductor 33. Accelerating switch I! thus responds to shunt the speed regulating rheostat l0.

The motor is thus started with full field strength and the inrush of current in the armature circuit thereof is sufficient to cause the load relay 26 to respond under the action of it windings 26* and 26 Upon response of the dynamic braking switch ill the contacts I!" thereof interrupt the aforedescribed energizing circuit for the forward contactors lI-l2. However, immediately upon depression of run button 20 the operating winding 25 of relay 25 is connected across lines L L through the medium of the stop push button 23. Relay 25 therefore responds and establishes a maintaining circuit for itself extending from line L through stop push button 23, through load relay 26, through its contacts 25 and operating winding 25 to line L. Relay 25 in responding also establishes a maintaining circuit for the forward contactors l l--l2 extending from line L through stop push button 23, through the load relay 26, through contacts 25 and contacts l2 of contactor i2, to and through the operating windings II and I! of said contactors, through auxiliary contacts 0 and d of contactor ii and by conductor 33 to line L As hereinbefore stated, the accelerating means for effecting progressive closure thereof upon establishment of power connections by either set of contactors -|i-l2 or |3-Hl, and said switches in closing exclude resistances R R and R and also the series field F. Upon closure of switch I! the auxiliary contacts I'l thereof interrupt the aforedescribed energizing circuit for the shunt coil l of accelerating switch 19 and said accelerating switch is then adapted to vibrate under the action of its series winding l9 to include and exclude the field regulating rheostat Ill. The motor is thus gradually accelerated and brought up to a speed determined by the setting of speed regulating rheostat [0.

As will now be set forth, regardless of the speed selected by the speed regulating rheostat ill, relay 26 will always operate to insure stopping of the motor when the material leaves the die or breaks during the drawing operation. As is apparent, when the material breaks or leaves the die the load on motor M drops to a value corresponding to the power required to drive the unloaded drawing mechanism. In practice it has been found that the power required to drive the unloaded drawing mechanism varies directly with the different drawing speeds and thus the torque of the motor when driving the unloaded drawing mechanism may be regarded as substantially constant. Thus for a given torque the armature current of motor M varies directly with the speed and there is therefore a wide variation in cur rent in the series winding 26 of the load relay 2B for different motor speeds. As hereinbefore set forth, during starting of the motor the load relay 2B is held in closed position under the action of its series winding 26 and its shunt winding 26 and the current in the latter winding is regulated by a rheostat 28 having its adjusting arm mechanically connected to the adjusting arm of rheostat ID. The arrangement is such that adjustment of speed regulating rheostat H) in a direction to increase the speed of the motor causes adjustment of rheostat 28 in a direction to decrease the current in winding 26, while adjustment of said speed regulating rheostat in a direction to decrease the speed of the motor causes adjustment of rheostat 28 in a direction to increase the current in winding 26". Thus by properly designing the rheostat 28 the load relay 28 can be made to drop out at various drawing speeds immediately upon unloading of the drawing mechanism and regardless of the fact that theremay be only a relatively slight reduction in load when the material leaves the die or breaks during the drawing operation.

Upon dropping out of relay 26 the aforede- 7s scribed maintaining circuit for the contactors lli2 and relay 25 are interruptedand saidtcontactors and relay then drop out to interrupt the armature circuit of the motor and to also interrupt the atoredescribed energizing circuit for the dynamic braking switch iii. The dynamic braking switch l6 then recloses to establish a dynamic braking circuit for the motor including resistance R and the operating winding 24 of relay 24. Relay 24 responds immedlately'upon establish ment of the dynamic braking circuit and in responding the same establishes an energizing circuit for the shunt operating winding l9 of accelerating switch l9, such energizing circuit extending from line L through said winding, through contacts 25 of relay 25, through contacts 24 of relay 24 and by conductor 33 to line L Accelerating switch l9 thus responds immediately upon establishment of the dynamic braking circuit to insure full current in the shunt field winding F during dynamic braking. In connection with the foregoing it should be noted that depression of stop push button 23 also effects deenerglzation of contactors ii and I2 and relay 24 and the motor will thus be stopped as hereinbei'ore described.

Relay 24 is held in its attracted position until the motor is brought substantially to rest and it will be noted that until said relay returns to normal position the contacts 1Z4 thereof prevent reestablishment of the aforedescribed energizing circuit for contactors ll-lZ.

Also it should be noted in connection with the foregoing that with the motor at rest the same can be inched in its forward direction by closure of push button 2i and in its reverse direction by closure of push button 22. Closure of push button 2% establishes the aforedescribed energizing circuit for the forward contactors H-l2. Closure of push button 22 establishes an ,energizingcircuit for reverse contactors III-44 extending from line L through stop push button 23 and push button 22, to and through the operating windings l3 and :14 of said contactors and through contacts 18 of the dynamic brakingswitch l8 and contacts 24 of relay 24 to line L Referring now to Fig. 2, the same schematically illustrates a well known type of draw bench including a movable carriage 36 which is provided with a set of pliers 31 for gripping the material to be drawn. Said carriage is releasably connected to a chain 38 which is adapted to be driven by a motor M of the character employed in Fig. 1. Also as in Fig. 1 the control means for motor M includes two sets of direction contactors i l--! 2 and I3l4; a plurality of accelerating switches l5, l6, H for shunting armature resistances R R and R and the series field F, a dynamic brain ing switch 18 for connecting resistance R across the terminals of armature A, an accelerating switch IQ for shunting speed regulating rheostat l and a relay 24 responsive to current in the dynamic braking circuit oi the motor.

The two sets of direction contactors Hl2 and l3-|4 are controlled by a normally open forward run push button 46, a normally open reverse inch push button 4! and a normally closed stop push button 42. Push button 40 provides for establishment of an energizing circuit for the forward contactors H-|2, while push button 4i provides for establishment of an energizing circuit for the reverse contactors' 13-44, such energizing circuits being the same as those described in connection with Fig. 1. However, in Fig. 2 the auxiliary contacts I2 oi contactor -52 are arranged to shunt push button 40 upon response of said contactor and the motor thus continues to operate when started in its forward direction until the energizing circuit for the contactors I l-l2 is interrupted by depression of the stop push button 42. The dynamic braking switch l8 and relay 24 also operate in the manner set forth in connection with Fig. 1 to effect dynamic braking of the motor for stopping and to insure against restarting thereof until the same is brought'substantially to rest. Also as in Fig. 1 the accelerating switches l5, l6 and ill are provided with suitable electromagnetic control means for effecting progressive closure thereof ,upon establishment of power connections for the motor by either set of direction contactors H--l2 or Iii-l4.

However. in the controller shown in Fig. 2 the control means for accelerating switch l9 includes a limit switch 43 and a plurality of relays 44, 45 and 46. The limit switch 43 is biased to open position and is arranged to be closed by the carriage 38 of the draw bench when such carriage is in its starting position. Relays 44 and 45 are or the conventional type and relay 46 is provided with a series operating winding 46* and a shunt operating winding 46*. Winding 46 is connected in the armature circuit of the motor and control means which will be hereinafter described is provided for regulating the current in the shunt winding 46' upon adjustment of speed regulating rheostat ill to insure dropping out of relay 46 when the draw bench becomes unloaded.

The function and operation of the aforedescribed draw bench controller and the circuit connections thereof will now be more fully described.

Under normal conditions the carriage 36 of the draw bench is released from its associated driving chain 38 and said chain is driven in its forward direction by motor M. As hereinbefore set forth, motor M is started in its forward direction by closure of the forward run push button 40 and upon starting thereof the switches i5, i6 and H close automatically to exclude the starting resistances R R and R and the series field winding F of the motor. Assuming that the carriage 36 is in its starting position the limit switch 43 is closed to establish an energizing circuit for the shunt operating winding 19* of accelerating switch 19, such circuit extending from line L through contacts 43 of said limit switch, by conductors 48 and 49 to and through the winding i 9 and thence through auxiliary contacts 1 and d of the forward contactor H to line L Thus with the carriage 38 in starting position, accelerating switch i9 is held in closed position by its winding I9 to shunt rheostat ill and thereby insure full current in the shunt field Winding F for slow speed operation of the motor. Also when the carriage is in starting position and released from its associated driving chain 38 the motor is unloaded and load relay 46 is in normal position. With load relay 46 in normal position, relay 45 is held in its attracted position by a circuit extending from line L through contacts 46 of relay 46 throughcontacts 43 of limit switch 43 and through the operating winding 45 of relay 45 to line L Relay 44 is also held in its attracted position by a circuit extending from line L by conductor 41 through contacts 45 of relay 45, to and through the operating winding 44 of relay 44 to line L Assuming now that a drawing operation is to be started, the carriage 36 is connected to the chain .38 and said carriage is then driven in its drawing direction by the motor M. Upon movement of the carriage 36 out .of startingposition, limit switch 43 opens to interrupt the aforedescribed energizing circuit for the shunt operating winding I! of accelerating switch I! and said switch then drops out to include the speed regulating rheostat ID in the shunt field circuit of the motor. The motor then accelerates and during acceleration thereof switch 19 vibrates under the action of its series winding I9 until the motor is brought up to a speed corresponding to the setting of speed regulating rheostat ID. The inrush of current in the armature circuit resulting from inclusion ofrheostat III in the shunt field circuit of the motor'causes response of the load relay 46.

It will be noted that upon opening of the limit switch 43 relay 46 is maintained energized by a circuit extending from line L by conductor 41 through contacts 46 of load relay 46, through contacts 45 of relay 45 and through the operating winding 45 of said relay to line 1?. However, upon response of the load relay 46 this energizing circuit for relay 45 is interrupted and said relay thus drops out. Dropping out of relay 45 interrupts the aforedescribed energizing circuit for relay 44. However, immediately upon response of load relay 46 relay 44 is maintained energized by a circuit extending from line'L to conductor 41 through contacts 46 of load relay 46 through contacts 44 of relay 44 and through the operating winding 44' to line L.

Upon completion of the drawing operation or upon slipping of the material out of the pliers 31 the motor becomes unloaded and the load relay 46 returns to normal position. The aforedescribed energizing circuit for relay 44 extending through the contacts 46 of the load relay'is thus interrupted and relay 44 returns to normal position to reestablish an energizing circuit for the winding I9 of accelerating switch l9 extending from line L by conductor 4| through contacts 44" of relay 44, by conductor 46 through the shunt operating winding 19 and through auxiliary contacts f and d of the forward contactor II to line L. Accelerating switch is is then moved into closed position to exclude the speed regulating rheostat In from the shunt field circuit to provide for operation of the motor at slow speed.

In connection with the foregoing it will be noted that relay 44 cannot be opened to deenergize the operating winding 19 of accelerating switch I! until the carriage is returned to starting position and upon return of the carriage to such position the aforedescribed energizing circuit for" said winding is reestablished by limit switch 43.

In some instances it is necessary to provide for high speed operation of the motor when the carriage is not in starting position. For this purpose a normally open push button 5| is provided which when closed connects the operating winding 44 of relay 44 across lines L U. The relay 44 can thus be energized at any time except when the carriage is in starting position to interrupt the aforedescribed energizing circuit for the shunt winding IQ of accelerating switch I! to cause dropping out of said switch and inclusion of the speed regulating rheostat I 6 in the shunt field circuit of the motor.

The means hereinbefore referred to for regulating the current in shunt winding 46' of relay 46 to insure dropping out of said relay when the draw bench becomes unloaded includes a rheostat 52 having its adjusting arm mechanically connected to the adjusting arm of speed regulating rheostat 10; a second rheostat 53 and three fixed resistances R Rand R". The shunt operating winding 46 of relay 46 is permanently connected between the adjusting arms of the rheostats 52 and'53. Rheostat 52 and resistance R are connected in series and resistance R is connected to line L while rheostat 52 is connected to line L. Resistances R and R are connected to lines L,

L respectively, and the rheostat 53 is connected between said resistances. The rheostats 52 and 53, resistances R R and R" and shunt coil 46 thus form a Wheatstone bridge circuit. Thus it is" apparent that by properly proportioning the resistance values, the direction of current in winding 46 of relay 46 can be controlled so that said winding will act to assist the series winding 46 upon setting of the rheostat 52 in positions corresponding to low running speeds and to oppose said series winding upon setting of rheostat 52 in positions corresponding to high running speeds.

In practice it has been found that by providing for reversal of the direction of current in winding 46 for different settings of the speed regulating rheostat 52 as above set forth said winding will operate with a relatively small number of ampere turns to insure dropping out of relay 46 at various drawing speeds immediately upon unloading of the drawing mechanism. Also it has been found that a relatively small number of ampere turns in the shunt operating winding 46 tends to minimize variations in the action of said coil which result from heating thereof or variations in the voltage of the supply circuit L L.

In practice it has been found that as the parts of the drawing mechanism wear in, the power required to drive such mechanism under unloaded conditions is decreased. It is therefore necessary to vary the setting of the load relay 46 to compensatefor such variations. As is apparent, by adjusting the rheostat 53 the current in the shunt winding 46 can be regulated to cause dropping out of relay 46 at proper no load current values in the series winding 46' for the various running speeds.

In connection with the foregoing it should be noted that the control means employed in connection with the load relay 46 of Fig. 2 can be employed for controlling the load relay 26 in Fig. 1.

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

1. The combination with a driving motor and a machine driven thereby, of means for establishing power connections for said motor and for regulating the running speed thereof, means asso ciated with said former means for automatically interrupting the power connections for said motor and for establishing a dynamic braking circuit therefor upon unloading of said machine, and means for preventing reestablishment of power connections for said motor upon given current conditions in said dynamic braking circuit.

2. The combination with a metal drawing machine, of a driving motor for said machine, means for starting said motor and forcausing operation thereof at a selected high runningspeed when the load on said machine exceeds a predetermined no load value, and means associated with said former means for automatically reducing the speed of said motor when the load on said machine is reduced to said no load value.

3. The combination with a metal drawing mechanism, of a driving motor therefor, means for starting said motor and for normally causing operation thereof at a predetermined slow speed, means for causing operation of said motor at a selected high running speed, but only upon movement of said drawing mechanism out of a given normal position, and means for controlling said aosmce last mentioned means to insure operation of said motor at said predetermined slow speed upon un-' loading of said drawing mechanism.

4. The combination with a metal drawing ma" chine, of a. driving motor therefor, means for starting said motor and for regulating the running speed thereof, a relay associated with said former means for reducing the speed of said motor upon a predetermined unloaded condition of said ma-' chine, said relay having a plurality of control windings, one of said windings being connected in the armature circuit of said motor and means for varying the excitation of the other of said windings in accordance with the running speed of said motor. o

5. The combination with a motor variable in speed by shunt field regulation, of field weakening means therefor providing for acceleration thereof to a predetermined high speed, and automatic means to include said field weakening means when the current in the armature circuit of said motor exceeds a predetermined no load value and for excluding saidfield weakening means when the current in said armature circuit drops below such no load value.

6. The combination with a motor variable in speed by shunt field regulation, of field weakening means therefor providing for acceleration thereof to a predetermined high Speed, and automatic means to include said field weakening means when the current in the armature circuit of said motor exceeds a predetermined no load value and connected in the armature circuit of said motor and a shunt operating winding having means associated therewith for regulating the same in accordance with the speed of said motor.

"I. The combination with a drawing machine, of a driving motor therefor, control meansfor starting said motor and for regulating the running speed thereof, means including a relay associated with said control means for checking the speed of said motor upon a predeterminedunloaded condition of said machine, said relay having a plurality of operating windings, one of said windings being connected in the armature circuit of said motor, and means for controlling the other of said windings to cause the same to assist said former winding upon operation of said motor at certain speeds and to oppose said former winding upon operation of said motor at other speeds.

JOHN M. NEWMAN.

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