US1531654A - Alternating-current motor-control system and control switch therefor - Google Patents

Description

March 31. 1925. 1,531,654

w. J. HUDSON ALTERNATING CURRENT MOTOR CONTROL SYSTEM AND CONTROL SWITCH THEREFOR Fiied .151. 25 1919 mvsufon' y $22 2 lMll/bmdflodsan' Patented Mar. 31, 1925.

-UNITED STATES PATENT OFFICE.

XVILLIAM J. HUDSON. OF MUSCATINE, IOWA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 013 PENNSYLVANIA.

ALTERNATING-CURRENT MOTOR-CONTROL SYSTELI 'AND CONTROL SWITCH THEREFOR.

Application filed January 25, 1919. Serial No. 273,074.

To all whom it maig concern:

Be it known that-I, VILLKAM .l. HUDSON, a citizen of the United States, and a resident of Muscatine. in the county of Muscatine and State oi Iowa, have invented a new and useful Improvementin Alternat-ing Current Motor-Control Systems and Control Switches Therefor, of which the following is a specification. My invention relates to alternating-current magnets and switches and has particular relation to the control of motors thereby. I

One object of my invention is toprovide an improved alternating-current magnet.

A second object of my invent-ion is to provide such a magnet which shall be cspet-ially adapted for short-circuiting the resistor in the secondary-winding circuit of a woundrotor induction motor.

Other objects will appear hereinafter and will be embodied in the appended claims.

According to the form ot'iny invention herein chosen for purposes of illustration, I provide a magnet core having three legs, upon the central leg of which is pivotally mounted an armature member having pole pieces for co-operating with the two end legs. reactive and resistive. are connected across the slip rings of the secondary winding of the motor. and are respectively wound upon the end legs. The armature member carries a switch member for'short-circuiting portions of the resistor which is in circuit with the secondary winding. The characteristics or" the two coils are such that at a lower speed than that for which the switch is set. the armature will be held in engagement with one of the end legs to maintain the switch open. As the motor speed increases. the switch will be closed by the arn'iature member being actuated into engagement with the other end leg.

My invention will be described in connection with the accompanying drawing. in which the single figure is a diagrammatic view of circuits and apparatus embodying my invention, the resistor which is in circuit with the wound secondary winding being shown as adapted to be shortcircui.ted in two steps by means of two switches embodying differentforms of my invention.

Line conductors 1, 2 and which may be connected to any suitable source of three- Coils. which are respectively mainly phase alternating current. supply energy to an induction motor 4} having a phase-wound secondary member. The secondary winding of the motor is connected through the usual slip rings to external resistors 5, 6 and 7. The resistors are controlled by switches 8 and 9. the switch 8 having a movable member 10 which. is adapted to close to engage stationary members 11. 12 and respectively connected to intermediate points of the resistors 5, 6 and T and the switch 9 having a movable member 14 adapted to close to engage stationary switch members 15, 16and 17, respectively connected to points between the secondary phase windings and the resistors 5, 6 and 7. The switch 8 will thus short-circuit, when closed, a portion of each of the resistors 5, 6 and 7 and the switch 9 the remaining portion.

The switches 8 and 9 each comprise a core member 18 havingend legs 19 and 20 and a central leg 21. Upon the central leg is pivotally mounted an armature member 22 having pole pieces 23 and 24 for cooperating with the end legs 19 and 20, respectively. The armature member 22 carries the movable switch member 10 or 14 which is adapted to he closed when the pole piece 23 has been actuated into engagement with the leg 19. The armature 2-2 is shown in the normal. inoperative position with the pole piece 24 engaging an adjustable. nonmagnetizable stop member 25 which is adapted to limit the movenjient of the. armature 22 with respect to the leg 20, thereby providing for different sized air gaps between the pole piece and the leg 20. The armature 22 is provided with a weight member 26 for actuating the armature 22 into the inoperative, illustrated position.

The legs 19 and 20 are respectively pro vided with coils 27 and 28, the former of which is mainly reactive and the latter mainly resistive. For purposes of illustration. I have shown a resistor 29 in series with the coil 28 but it will be understood that the necessary resistance may be embodied in the coil itself by suitably winding properly chosen material. The coils 27 and 28 are connected in parallel across conductors 30 and 31, which are respectively connected across two of the slip rings of the secondary winding.

The operation is as follows. \Vhen the motor has been started, by connecting the primary windings to the line through the closing of a switch, not shown, current will be induced in the secondary windings and will flow through the resistors 5, 6 and 7. The motor will then begin to speed up. It will be obvious that by reason of its connections, and its nature, the coil 27 will be responsive to both voltage and frequency, so that it will exert a force upon the arma- V ture 22. which is approximately constant for all speeds of the motor. The other coil 28,

being responsive to voltage principally, the I force exerted by it upon the armature 22 will depend upon the speed of the motor.

' As the motor speed increases, the frequency andthe'voltageimpressed on the two coils decrease in proportion to the percent slip. The flux produced by the coil 28 will ultimatelydecrease to a value less than that created by approximately constant force of thecoil 27, whereupon the pole piece 23 of the; armature 22 will be actuated into eng agement with-the leg 19, closing the switch members 10, 11, 12 and 13 (assuming that the switch 8 has been adjusted to close be- I fore the switch 9) and resulting in short circuiting a portion of the resistors 5, 6 and 7 The motor speed; then further increases and ultimately the coil 27 will overpower the coil 28 of the switch 9, causing the closure of the switchmembers 14, 15, 16 and 17. The resistors 5, 6 and 7 are now entirely short-'circuited and themotor is running at 1 normal speed. A holding coil 27?, controlled by line voltag'e, is employed to maintain switch '9 closed. ,Any other well known holding means may be employed.

In the'abovedescription of the operation, it-hasbeen assumed that the switch 8 will close before the switch 9. This is not because of theparticular structure illustrated, but as a result of proper design of the coils, the adjustment of the stop and the size of the Weight member 26. Obviously, any number of these switches may be employed,

anyor all of which may be of the type indicated at ,8 or 9. It willbe understood that 7 to, a switch for short-circuiting said resistor,

means including shunt; circuits from said motortor controlling said switch in accordance with the relation between the reactance and the resistance of'said circuits.

2. The combination with an alternatingcurrent motor having primary and secondary windings and a resistorin circuit with said secondary winding, of a switch for short-.circuiting said resistor having reactive and resistive opposing actuating coils,

connected across two leads of said secondary winding; H a I.

a 3. The combination with. a, dynamo-electric machine,of-atranslating device connected thereto, means adapted to render said device 'inefiective, and. means including shunt circuits from said machine for controlling the first-named meansin accordance with the relation between the reactance' and the resistance of said circuits. r

4.- The combination with a dynamo-electric machine having co -operating stationary and movable'windings and a resistor in circuit with one of saidwindings, of a switch for rendering said resistor ineffective and having reactive and resistive actuating coilsconnected across a portion of said resistor.

In testimony whereof,'I have hereunto subscribed my name this 11th day of Janu-. ary, 1919. i

- WILLIAM J. HUDSON.

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