Regulator for electric motors
US 558517 A
Description (OCR text may contain errors)
0. H. PIEPER.
REGULATOR FOE ELECTRIC MOTORS.
No. 558,517. Patented Apr. 21, 1896.
UNITED STATES PATENT OFFICE.
OSCAR ll. PIEPER, OF ROCHESTER, NE\V YORK.
REGULATOR FOR ELECTRIC MOTORS.
SPECIFICATION forming part of Letters Patent No. 558,517, dated April 21, 1896.
Application filed January 20,1896. Serial No. 576,178. (No model.)
To all whom, it may concern.-
Be it known that I, OSCAR ll. PIEPER, of Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Regulators for Electric Motors; and I do hereby declare the following to be a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming a part of this specification, and to the reference numerals and letters marked thereon.
My invention relates to means for varying the speed of shunt-wound electric motors, whereby the resistance of the armature and field circuits is so proportioned that at low speeds the field-magnets become stronger, and the current in the armature is increased, thereby increasing the torque or turning power of the armature at low speeds, so that the speed of the motor will vary but little under extreme variations of load, all as will be hereinafterfully described, and the novel features pointed out in the claims at the end of this specification.
In the drawings, Figure 1 is a diagrammatic view of a shunt-W0 und motor and the circuits arranged in accordance with my invention, showing the position of the switch when the motor is running at low speed; Fig. 2, a similar view of the switch, showing the motor operating at a greater speed; Fig. 3, a view showing the motor at full speed.
Similar reference numerals and letters in the several figures indicate similar parts.
The shunt-wound motor A, of usual construction, is provided with the field-coils B, and the usual commutator-brushes C 0, operating on the commutator on the armature and supplied with a constant potential current from the mains or conductors and the direction of the current through the motor and switch devices being indicated by the arrow-heads.
D indicates a switch-lever connected by the wire 1 to one of the mains, one end of which is adapted to rest upon the two conductingsegments E and F having at their ends small contact-pieces E and F, respectively, connected with their respective segments through suitable resistances E and F, the end plate E being connected by the wire 2 with one of the brushes G of the commutator, and the plate F being connected by the wire 3 with the field-coils. On the opposite end of the switch-lever D, but insulated therefrom, is a contact-plate D, arranged to slide over a segmental plate D connected by a conductor it with the leading-in wire 2 of the armature, and arranged in proximity to this plate D is a series of contacts G G G connected by resistance-coils g g, and the end contact G is connected by a wire 5 with the leading-in wire of the field-coils.
Vhen the machine is at rest, the switch-lever is in the position shown in dotted lines in Fig. 1, and when the motor is operating at slow speed the switch-arm is moved to the position shown in f ulllines in Fig'. 1, the current then passing from the conductor through wire 1,switchle"er D,segment E, and through resistance E to the leading-in wire 2 of the armature, thence by wire 6 to the conductor and a portion of the current passes from switch-arm D through segment F, resistance F to the leadingdn wire 3 of the field-coils, through the latter, and by means of conductor 7 to the line conductor In the position shown in full lines it will be noticed that the leading-in wire 2 of the armature and the leading-in wire 3 of the field-coils are connected by means of conductors 4t and 5, switch-arm D, segment D and contacts G or G through the variable resistance embodying the coils g, 0 9
In Fig. 2, when the motor is running at greater speed than when as shown in Fig. 1,the switch is moved so that the variable resistance g g is cut out of circuit and the motor is then operating as an ordinary shunt-wound motor, excepting for the resistances E and F in circuit with the leading-in wires to the armature and to the field-coils, respectively, and when running at greatest speed the switch is in the position shown in Fig. 3, the resistances E and F then being out of the circuit if the motor is one adapted to the full voltage of the main; but if not the resistances E and F are left in circuit, though the branch is opened, as in Fig. 2.
From the above it will be seen that when the motor is running at slow speed and the greatest amount of torque is required there is a resistance in series with the field-magnet winding, a resistance in series with the armature, and also a branch connected across between one wire or conductor of the field and the corresponding wire or conductor of the armature containing a variable resistance, which is gradually increased as the speed is increased, and finally the branch is opened.
With my improved method of varying the speed of shunt-wound motors, by proporti0ning the resistance of the armature and field winding, so that at low speeds the field-magnets become stronger and the available volts at the armatureterminals are reduced, because of the path of lower resistance by way of the magnet-coils, the armature speed being reduced as a result of the two conditions, the resistance placed in series with both the armature and field practically makes constant current-circuits of each of these, with virtually only a given amount of current available.
Vith the aforesaid variable resistances g g cut out of circuit the field-current will remain constant; so also will the armature-current under a steady load; but all of the current capable of passing through the series armature resistance is not flowing, due to the counter electromotive force of the armature. It is evident then that if a circuit of low resistance be inserted between the armature leadin g-in wire and-the field leading-in wire more current will flow through the series armature resistance to the field-windin gs, thereby strengthening the magnets and accomplishin g areduction of speed, but all the additional current now flowing through the series armature resistance does not go to the field-winch ings, a portion also going to the armature, the counter electromotive force having been reduced.
Motors regulated in the manner and by the means described will change but slightly in speed under extreme variations of load, the torque becoming greatest at lowest speed.
The resistances E and F are always left in circuit when my invention is employed in motors which are not adapt-ed to receive and utilize the full current from the main eonductors, but they may be cut out by the continued movement of the switch when the device is used in large motors practically adapted to the voltage of the mains supplying them.
It will be understood that while I prefer to arrange the branch containing the variable resistance between the leading-in conductors of the field and armature, respectively, it is only necessary that the corresponding conductors be connected by said branchthat is, either the leading-inor leading-out wires.
I claim as my invention 1. The combination with a shunt-wound motor, of a variable resistance capable of variation when the motor is running connected across between one wire or conductor of the field and the corresponding wire or conductor of the armature, substantially as described.
2. The combination with a shunt-wound motor, of a resistance in series with the fieldmagnets, a resistance in series with the armature, and a branch containing a variable resistance between corresponding conductors of the field and armature, substantially as described.
3. The combination with a shunt-wouiul motor, a resistance in series with the fieldmagnets, a resistance in series with the armature, and a branch containing a variable resistance between corresponding conductors-of the field and armature, of a switch-arm and contacts controlled by it, whereby as it is operated in one direction the resistanceis gradually increased in the branch, then the branch is opened and finally the resistances in series with the field and armature are cut out, sub stantially as described.
OSCAR ll. PIEPER.
F. F. CHURCH, Gnncn A. Rona.