USRE16947E - Sylvania - Google Patents

Description

May 1, 192 8.

H. w. WILLIAMS MOTOR CONTROL SYSTEM Original Filed Sept. 8. 1925 vW T w L 0 f 2 mooo 0 w o 0 o Reias ued M... 1, 1928.

@UNIT D STATES PATENT OFFICE.

HAROLD W. WILLIAMS, OF EAST I'ITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WEST- INGHO'USE ELECTRIC & MAN UFACTUBING COMPANY, A CORPORATION OF PENN- srnvama MOTOR-CONTROL SYSTEM.

Original Ho. 1,549,698,-dated August 11, 1925, Serial No. 661,588, filed September 8, 1923, Application for reissue filed August 10, 1927. Serial 110. 212,114. Y

I My invention relates to motor-control sys-,

tems and it has particular relation to .such systems of control as are employed in connection with elevators, machine tools and similar machines;

An-object of my invention is to provide means forcontrolling the speed and the torque of an alternating-current motor of the two-speed type commonly employed in ele vator service and having separate low and high-speed windings.

My invention is more particularly applicable to the control of a two-speed'motor of a well-known squirrel-cage type.

In the operation of alternating-current motors of the type herein described,;it is common practice to start the motor by connecting its low-speed winding to the source and provide means for ensuring a relatively weak excitation of the low-speed windings.

Next, the low-speed windings are shunted and the excitation of the high-speed .windings is increased'to its maximum value.

In systems heretofore known it has been essential that a definite sequence of operation of the transition switches be maintained: otherwise the motor either lost torque or the supply circuit was short-circuited, depending upon whether the corresponding .phases of the two windings wereinitially'conn'ected in series or in parallel relation. As is hereinafter described, with my system the sequence of operation of the transitionswitches is not material, neither loss of torque nor short circuit being caused, regardless of the sequence of operation.

To efiect deceleration of the motor, the speed windings are first connected in the -plfeviously named parallel relation, after which the high-speed windings are de-en'ergiz jed and finally the excitation of the lows'p'd windin is increased to obtain a mindesira 1e operation speed. Again, ppyelverpthe sequence .of transition is mm no. j a

been My invention willbe described in connection with the accompanying drawing, in.

which Figure 1 is a diagrammatic representation of a two-speed,three-phase, alternating-current squirrel-cage motor employed in connection with my invention,

. Fig. 2 is a diagrammatic representation of v the main circuits and apparatus embodying my nvention,

Fig. 3 1s a diagrammatic representation of i the control circuits that are employed in the operation of the system shown in Fig. 2, and Fig. 4 isa sequence chart indicating the operation of switches employed in Fig. 2.

Referring to the drawing, a two-speed alternating-current motor 1 is provided with low-speed primary windings 2' and high-' speed primary'windings 3. These windings are connected in series relation with a plurality of reactors 4: and 5, which are respectively employed for low-speed and for high-speed operation- Resistor sections 6 are arranged for connection in circuit with the high-speed windings 3 through a switch 7. A three-pole switch 8 provides means for shunting the high-speed windings 3 and rendering the low-speed windings 2 effective. Double-pole reversing switches 9 and 10 are Poremployed in the customary manner. tlons of the -low-speed.-reactors 4; may be shunted by a double-pole switch 11 that is provided with a retarding device 12.

1 "Also, a double-pole switch '13 is arranged.

for shunting resistor sections 6. This switch is also provided with retardi'n means. Both switches 11 and 13 are retar ed only in closing. The various switches are operated by means'of a reversible master switch 23 of a familiar type having a plurality of operating positions a, b, c and d. A source of power-supply for the motor comprises line conductorsl, 15 and 16. I have n illustrated connections for a three-phase induction motor, but, of course, a two-phase motor or motors of other suitable types may be similarly employed.

Assuming the apparatus to be in its inoperative or illustrated positions, the motor 1' ma be operated in an upward direction 7 actuatin the left. In position a see sequency chart, Fig. 4) a circuit is provi the master switch 23 to ed for eflectin the closure of reversing switch 9 and CW! in a well-known manner.

speed switch S. 7 Power is then supplied to the motor windings 2, with reactors 4 in circult therewith. If master switch 23 is maintained in position a, switch 11 will close to shunt a portion of reactors 4, whereby the motor is provided with sufiicient torque to start the desired maximum load. A lightload may be started prior to the closure of switch 11. However, the primary object of the additional sections of reactors 4 will hereinafter appear.

\Vheu the master switch 23 is actuated toward posit-ion I), switch 7, may close prior to the opening of switch 8, whereupon highspeed windings 3 are connected, through resistor sections 6 in parallel relation to lowspeed windings 2. This osition affords a transition period or, if desired, may serve as an operating position in which the motor operates at a speed intermediate its minimum and maximum speeds, depending upon the degree of excitation of the low-speed windings 2.

When the master switch 23 is moved to position I), switch 8 opens and the motor is further accelerated in accordance with the excitation of the windings 3. Finally switch 13 closes'to shunt resistors 6, where upon the motor operates at its maximum speed.

It should be noted, in .connection with the foregoing description, that the motor speedwindings are at no time disconnected nor is the power supply interrupted so that a fairly uniform torque is developed by the motor in accordance with the arrangement of the reactors and resistors which are, of course, designed for limiting the currents The motor is decelerated by returning master switch 23 toward the ofi positions, passing through position a. Switch 8 is reelosed, re-establishing the above-described parallel relation of motor windings 2 and 3, and, upon the re-opening of switch 7, the

high-speedwindingsti are de-energized and the motor is further decelerated, since only the low-speed windings 2 are then energized. Switch 11 starts to close but is re-\ tarded for a suflicient period, whereby the torque of the motor, which is for the moment operating above its lower synchronous speed, is suitably reduced. The effect of the additional reactor sections 4, which are controlled by switch 11, is to prevent a too abrupt change in the speed of the motor, occasioned by its regenerative action. Sulficient time is allowed for the closure of switch 11 so that the motor speed is first suitably reduced. Under slow speedconditions, reactors 4 have little effect upon the speed regulation of the motor so that it is, ordi- -narily, unnecessary to provide means for entirely shunting these reactors from the circuit. If it is desirable tooperate the motor According to my invention, I am enabled to accelerate and decelerate a motor having separate high and low-speed windings without disconnecting; these windings, whereby a fairly uniform torque is obtainable and, cons sequently, smooth and flexible speed'control. Also, the switching arrangement is such that the line conductors cannot be short-circuited by failure of any of the speed-controlling switches to function.

In the arrangement of apparatus, as illustrated in- Fig. 2, it is possible to provide for a different sequence of operation and to obtain still other operating speeds as, for example, when both the high and low-speed switches 7 and 8 are open, and the motor windings are all connected in series relation. Resistors may besubstit-uted in place of reactors 4 and 5, when desirable, but I prefer to employ the arrangement illustrated, particularly for hoisting applications,

Operation of the motor in a reverse direc-' tion is obtained in a manner similar to that described above, upon the closure of reversing switch 10 in place of reversing switch 9 by the manipulation of master switch 23 to the right, through positions .0 and d, as will be readily understood.

I have described and illustrated my invention in simple form, but various modi fications may be made therein Without departing from the spirit and scope thereof.

I claim as my invention: 1. The method of accelerating an alternating-current motor having low and highspeed' windings connected in series relation,

which consists-in shunting the high-speed windings, connecting said high and lowspeed windings in parallel relation, diminishing the effect of said low-speed windings and finally shunt-ing said low-speed wind- IDES.

2. The method of accelerating an induction-motor having low and high-speed windings connected in series relation, which consists in energizing the low-speed windings,

connecting said low and high-speed windings in parallel relation, lessening the effect of said low-speed windings, and finally,

shunting said low-speed windings.

3. The method decelerating an alternating-current motor having low and highspeed windings connected in series relation, which consists in connecting the low and high-speed windings in parallel relation when the effect of the low-speed windings.

is relativelvweak, disconnecting said highspeed windings and strengthening the effect of the low-speed windings.-

4. The combination with an alternatingcurrent motor having low' and high-speed Windin connected in series relation and ing said windings,

' and for connecting said windings t e reactors alternating in position with said windings, 'of'means for selectively shunting said windings and for connecting said windings in parallel relation without interrupting the motor circuit.

5. The combination with an alternating-v current motor having low and high-speed windings connected in series relation, and reactors alternating in position with said windings, of means for selectively shunting said windings and for connecting said windings in parallel relation without disconnecting said windings.

6. The combination with an alternatingcurrent motor having low and high-speed windings connected in series relation, and current-limiting means alternating in position with said windings, of means for selectively shunting said windings and for connecting said windings in parallel relation without interrupting the motor circuit.

7. The combination with an alternatingcurrent motor having low and high-speed windings connected in series relation, and current-limiting means alternating in position with said windings, of means for selectively, shunting said windings and for connecting said windings in parallel relation without disconnecting said windings.

8. The combination with an alternatingcurrent motor having low and highspeed windings connected in series relation, and reactors in circuit with said windings, of means for'selectively shuntin said windings in parallel relation without interrupting motor circuit. 9. In a control system for multi-phase alternating current motors having high-speed windings and low-s eed windings, a source of power, a switch or each winding, a. current-limiting device, and means for connectsaid switches and said device to said sourcewhereby transition from one winding to the other winding may be made with at least one of said windings active at all times regardless of the .sequence of operation-of said switches.

10. In a control system for multi-plhase alternating current motors havin ighspeed windings and low-speed win ings, a source of power, a switch for each of said windings, means for selectively opei'ating said switches, a current-limiting device, and

means for connecting said windings, said switches and said device to said source of power whereby operation of said switches will connect said windings in series relation or in parallel relation or either winding alone to said source of power. 7

11. In a control system for multi-phase alternating current motors havin highspeed windings and low-speed win ings, a source of power, a switch for each' of said windings, means for selectively operating series relation, said v ces being severally dis said switches, a current-limiting device, and

means for connecting said windings, said switches and. said device to said source 0 power whereby operation of either of said switches will connect the correspond mg windings to said source. exclusive of the other, operation of both of said switches will connect said windings to said source in parallel relation and non-operation of both of said switches willconnect said windings to said source in series'relation.

12. In a control system for multihase alternating current motors, having a lighspeed winding and a'low-speed winding, 2.

means connectto said 'wmdlngs ing said source of-power at will, means said phase of series relation with thecorresponding use of said low-speed winding, a, currentimiting device connected" therebetween, means multi-phase source of power,

for shunting each phase of said high-speed winding and its associated current-limiting device, and means for connectin all of the phases of the high-spec windings at oints between for permanently connecting said high-speed windin in together the high-speed windings I an their associated current-limiting devices.

13. In' a control system for multi-phase alternating current motors having a high-.

speed winding and a low-speed winding, 3. multi-phase source of power, means for connecting said source of power ings at will, means permanently connecting each phase of said high-speed winding in to said windseries relation with the corresponding hase means.

14. In a control system for multihase alternating current motors having a ighspeed windin and a low-speed winding whereby transition from one winding to the other'may be accomplished without loss of torque and without short-circuit, the combination of a plurality of current-limiting devices, means for permanently connecting corresponding phases of said high-speed windings and said low-speed windings in current-limiting deosed therebetween, switch means for simu taneously shunting the high-speed phase windings and their associated current-limiting devices, and switch means for simultaneously connecting to- Phases f said high-speed windings and said ow-speed windings in series relation, said reactors being severally disposed therebetween, switch means for simultaneously 1!; shunting the high-speed phase windings and their associated reactors, and switch means for simultaneously connecting together all of the phases of said high-speed winding at points between said windings 20 and said reactors.

' HAROLD W. WILLIAMS.

Images