US374910A - Regulation of electric motors - Google Patents

Description

' 3 Sheets-Sheet 1.

(No Model.)

w. STANLEY, Jr.

REGULATION OF ELECTRIC MOTORS.

Patented Dec. 13, 1887.

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W. STANLEY, Jr.-

REGULATION OF ELECTRIC MOTORS.

No; 374,910. Patented Dec. 13,1887.

(NO Model.) 3SheetsSh'eet 3.

, W. STANLEY, Jr.

REGULATION OF ELECTRIC MOTORS.

NO. 374,910. Patented Dec. 13, 1887.

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UNITED STATES PATENT OFFICE.

WILLIAM STANLEY, J R. OF ENGLEWOOD, NEW JERSEY, ASSIGNOR TO GEORGE WESTINGHOUSE, JR, OF PITTSBURG, PENNSYLVANIA.

REGULATION OF ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 374,910, dated December 13, 1887.

(No model.)

To aZZ whom it may concern:

Be it known that I, WILLIAM STANLEY, J r., of Englewood, in the county of Bergen and State of New Jersey, a citizen of the United States, temporarily residing at Sewickley, in the county of Allegheny and State of Pennsylvania, have invented or discovered certain new and useful Improvements in Regulation of Electric Motors, of which improvements the following is a specification.

In the accompanying drawings, which make part of this specification, Figure 1, Sheet 1, is a diagrammatic view of an electric motor and a regulating apparatus,i1lustrating the application of my invention when a constant quantity of current is supplied; Fig. 2, Sheet 2, a similar view illustrating the application when a constant difference of potential is supplied; and Figs. 3 and 4: similar views exemplifying modifications in the arrangement of the demagnetizing-cireuit.

The object of my invention is to effect the regulation of an electric motor to a determined constant speed, as may be required by the work to be performed by the motor, so as to prevent variation of speed under increase or diminution of duty or load.

To this end my invention, generally stated,

consists in a novel apparatus for increasing and decreasing the development of energy from an electric motor in accordance with and proportionately to variations in the work or load imposed by automatically decreasing and increasing the electromagnetic effect of a demagnetizing-circuit upon the field-magnet of the machine, said apparatus consisting in the combination, with an electric motor, of a demagnetizing field-circuit, a resistance line or coil, and an automatic switch mechanism adapted to shunt a greater or less length of said resistance-line into the demagnetizingcircuit proportionately to decrease or increase, respectively, of the work of the motor.

The improvements claimed are hereinafter fully set forth.

In the operation of electric motors it is desirable and in many cases essential to a proper and effective performance of their work that a uniform speed should be maintained irrespective of the temporary variations in the resistance imposed by the partial cessation or the additional imposition of work, as in the case of the illumination of a greater orless number of electric lights or the operation of more or less machinery from time to time. Motors employed in such service may be operated under either of two different conditionsfirst, where the electric energy actuating the motor is supplied as a constant quantity of current flowing through a line, in which case the electro-motive force applied to the terminals varies as the work performed, and, second, where a constant electro-motive force or difference of potential is applied to the terminals of the motor, in which case the quantity of current flowing through the motor will be varied proportionately'with variations in the work.

My invention, which is equally applicable under either of the above-stated conditions, affords ready and effective means for insuring the maintenance of such speed of the motor as may be suitable or requisite for the performance of the particular duty to which it is as signed.

Referring first to the case of a motor adapted to use in a line supplied with a constant quantity of current, Fig. 1 illustrates a construction adapted to the practice of my invention. The motor, which may be of any suitable and preferred construction, is here shown as provided with magnet-cores 1O 11, provided with pole-pieces 12 13, between which an armature, 14, is adapted to rotate in the usual manner. The electriceurrent which actu'ates the motor passes from a generator or other suitable source of supply through an energizingcircuit composed of a wire, 1, connected to one of the terminals, 8, a wire, 2, wound upon the magnet-cores 10 11 and leading from the terminal 8 to one of the brushes, 15, of the armature 14, a wire, 3, wound around a regulating electromagnet, 4, and extending from the other brush, 16, to the opposite terminal, 9, and a wire, 5, leading from the terminal 9 to the generator.

A demagnetizingcircuit, which is praetically a shunt across the terminals of the mo tor, is formed by a finer wire, 6, leading from the terminal 8, and wound around the magnet-cores 1O 11, to a connection with a resistance line or coil, 7, from which a series of connecting-wires, 17, extend at different points in 1ts length to contact-plates 18. The demagnetizing-circuit on the opposite side of the resistance line or coil 7 extends through an automatic switch-lever, 20, pivoted at one end by a link, 23, to the armature 22 of the regulating-magnet 4, and adapted to make contact, as raised or lowered by the movements of the armature, with either of the different contaet-plates 1S, and wires 24 25 lead from the switch-lever 20 to the terminal 9 of the motor. The fine wire of the demagnetizing-circuit is of comparatively high resistance relatively to the coarser wire of the energizing-circuit, and consequently takes a smaller portion of the current, and when the motor is in motion the quantity of current flowing through the demagnetiziug-circuit is proportional to the counter electro-motive force of the motor and the resistance of the energizing-circuit is less than that of the demagnetizing-eircuit. \Vhen the current is turned on the motor from the generator, the regulating magnet i raises the switch-lever 20 and holds it with its free endin contact with the plate 18, which is connected with the fartherextremity of the resistanceline 7, thereby throwing a maximum of resistance into the demagnetizing-circuit until the motor has obtained through the revolutions of its armature sufficient counter electro-motive force to cause the resistance of the energizing-circuit through the wires 2 3 to exceed that of the demagnetizingeireuit through the wire 6, resistanceline 7, connection 17, contact-plate 18, switch-lever 20, and wires 24 25.

Such increase of resistance, by demagnetizing the regulating magnet 4, allows the switeL- lever 20 to fall back to the position shown in the drawings, in which the minimum of resistance is shunted into the demagnetizing-circuit and the demagnetizing effect of said circuit is at its maximum, such demagnetizing effect tending to reduce the counter electro-motive force by demagnetiziug the field-magnets of the motor. If, now,aload be added,the amount of current flowing through the energizing-circuit will be increased by reason of the decrease of counter electro-motive force due to the slowing up of the armature. Thisincrease of current excites the regulating magnet 4E and causes it to lift the switch-lever 20, thereby increasing the resistance of the demagnetizingcircuit by throwing in a greater length of the resistance line or coil 7, such increase of resistance correspondingly increasing the speed of the motor, both by reason of the decrease of the demagnetizing effect of the demagnetizing-circuit and of the increase of the magnetizing effect of the energizing-circuit, due to the arrangement of the two circuits as shunts to each other. The movement of the switch-lever in direction to increase resistance continues until the counter elcctro-motive force has risen sufficiently to decrease the quantity of current through the energizingcircuit, and thereby to stop the upward pull of the magnet. If, on the other hand, the mechanicalload be decreased, the revolutions of the armature will be momentarily increased, the counter eleetro-motive force will be increased, and the regulating-magnet 4 will thereby be weakened. The resistance of the demagnetizingcircuit will consequently be decreased by the lowering of the switchlever, and a greater quantity of current be permitted to flow through said circuit, such increase of current demagnetizing the magnets of the motor and reducing its speed to the degree required.

Fig. 2 illustrates a construction applicable in cases where a constant difference of potential between the terminals 8 9 of the motor is em ployed. The current of the energizing-circuit passes through the wire 1 to the terminal 8 of the motor, thence through the wire 2, wound upon the magnet-cores 1O 11, to one of the brushes, 15, and from the other brush, 16, through a wire, 3, wound upon the regulatingmagnet 4, to a connection, 26, at which it is di vided, a portion passing through a demagnet izing-circuit composed of a wire, 27, leading to a binding-post, 28, on the motor, anda wire, 6, leading from the binding-post 28 to the terminal 9 and wound upon the magnet-cores 10 11. The other portion of the current passes as a shunt to this circuit, having a variable resistance formed by the wire 29, switch-lever 20, contact-plates 18, connections 17, resistance line or coil 7, and wire 30.

WVhen current is not turned on to the motor, the armature of the regulating magnet not being attracted,the connected end ot'the switchlever is in its lowest position, as shown in the drawings, and consequently the maximum rcsistanceisthrownintotheshunt-circuit.- Upon the application of a current to the motor the regulating-magnet 4, being excited, lifts the switch-lever 20, and by cutting out a portion of the variable resistance allows a greater quantity of current to flow through the shunt circuitwires 29 30 to the terminal 5 and aless quantity through the demagnetizirig-circuit, and the motor consequentlyincreases its speed until the counter electro-motive force rises sufficientl y to reduce the strength of the regulating-magnet and increase the resistance of the shunt-circuit to the required degree. Under such construction the strengthening of the regulating-magnet cuts out resistance in lieu of throwing in resistance, as in' the case first described; but in both the same rcsult--to wit, the reduction of the effect of the demagnetizing-circuit-is attained by the strengthening of the magnet.

It will be obvious that the arrangement of circuits may be modified in sundry particulars without departing from the spirit of my invention, so long as a regulating-magnet and variable resistance are employed to vary the field strength of a motor by varying thestrength YOU counter electro-motive force of the armature is highest, while in the construction shown in Figs. 1 and 2 the magnetic strength of the regulating-magnet decreases when the counter electro-motive forceis highest. Again,in Fig. 3 the upward movement of the armature of the regulating-magnet decreases the variable resistance, while in Fig. 1 the upward movement of said armature increases the variable resistance.

The specific regulating mechanism herein 3 shown does not per se constitute part of my present invention, and need not therefore be at length described, as other devices may be equivalently employed in the practice of my invention to attain the result effected thereby. Said mechanism, moreover, constitutes the subject-matter of another application for Letters Patent filed by me of even date herewith.

In lieu of employing a demagnetizing-coil, as hereinbefore described, the same may be omitted and thefield strength of the motor may be varied by simple shunts around the field-magnet coils; or the field-coils resistance mayitselfbevaried. Such arrangements,however, differ from myinvention in the essential particular that all the energy expended in the circuits by which the field-coils resistance is varied is lost, While the energy exerted in a demagnetizingcoil affects the motor in a similar manner to that of a generator, tending to advance the direction of the current; or, more simply, the result of the effect of the energizing and demagnetizing coils in the motor is such as would be produced by a generator and a motor combined in one machine, the generator acting as a brake to the motor. Regulation may further be effected under my invention with the employment ofa comparatively small resistance, which is particularly desirable in dealing with currents of great intensity.

resistance in said circuit coincidently with and proportionately to variations in the mechanical duty of 1 the motor, substantially as hereinabove set forth, is not herein claimed, as the same will constitute the subj cot-matter of a separate application for Letters Patent by me.

I claim herein as my invention- 1. In an electric motor, the combination of an energizing field-circuit, a demagnetizing field-circuit, a variableresistance located therein as a shunt around a regulating-magnet whose strength is controlled by the counter electromotive force, and an automatic switch mechanism actuated by said magnet to increase or decrease the quantity of resistance in the demagnetizing field circuit by Variations 1n counter electro-motive force effected by variations in the speed of the motor, substantially as set forth.

2. In an electric motor, the combination of a shunt-circuit around the terminals of the motor, a demagnetizing-coil upon thefieldmagnet of the motor and included in said circ'uit, a regulating-magnet, a variable resistance in a shunt around the regulating-magnet, and an automatic switch mechanism actuated by the regulating-magnet to shunt a greater or less proportion of said resistance into the circuit of the demagnetizing-coil in inverse proportion to the counter electro-motive force of the motor, substantially as set forth.

3. In an electric motor, the combination of a main or energizing circuit, a regulatingmagnet in said circuit, a shunt-circuit to the motor, including a demagnetizing field-coil, a variable resistance, and an automatic switch mechanism operated by the regulating-magnet to vary the amount of resistance in the demagnetizing-coil inversely as the counter electromotive force and speed of the motor, to the end of maintaining a constant determined speed thereof, substantially as set forth.

In testimony whereof I have hereunto set my hand.

\VILLIAM STANLEY, JR. \Vitnesscs:

J. SNowDEN BELL, F. O. MILLER.

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