US 714412 A
Description (OCR text may contain errors)
No. 7:4,4|2 P atented Nov. 25, 1902.
c. P. STEINMETZ. INDUCTION MOTOR.
Application filed May. 22, 1900.,
(No Model. 2 Sheets-Sheet 2,
Mmjses. Inventor @744 U) charles fiteihmetz fitt UNITED STATES PATENT OFFICE.
CHARLES P. STEINMETZ, OF SOHENEOTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.
SPECIFICATION forming part of Letters Patent No. 714,412, dated November 25, 1902.
Application filed March 22, 1900. Serial No. 9,661. (No model.)
T0 at whom, it ntay concern:
Be it known that 1, CHARLES P. STEINMETZ,a citizen of the United States, residing at Schenectady, in the county of Schenectady and State of New York, have invented certain new and useful Improvements in Induction-Motors, (Case No. 1,195,) of which the following is a specification.
This invention relates to ind notion-motors, the object being to permit a safe and effective starting of the motor.
The invention relates to induction-motors of that type in which a squirrel-cage winding is employed on the secondary element, the object being to produce an economical and effective starting of the motor by giving the secondary winding an increased resistance when the motor is first cut in and then gradually decreasing the said resistance as it rises in speed. In starting induction-motors a tremendous rush of current due to the great slip causes the secondary poles to overpower those of the primary element and gives the motor a low starting torque. In order to prevent this objectionable result,means are commonly provided for cutting resistance into the secondary circuit while the motor is starting in order to prevent a blowing out of the primary poles and to increase the starting torque, such resistance being cut out as the motor rises in speed. I provide for the effective starting of such motors by mounting on the secondary element a winding normally kept on closed circuit by means of a high resistance, but capable of being connected up in a series of progressively-decreasing resistance paths as the motor rises in speed. Means have heretofore been provided for effecting a similar result on an induction-motor having a wirewound secondary, but have usually been complicated in construction or required rubbing contacts and outside connections. In my organization I employ a high-resistance connection normally completing the closure of a squirrel-cage winding and which is in circuit at all times and a series of elastically-yielding conductive disks mounted so as to be shifted to or from the conductors of the winding to progressively decrease or increase its resistance. The conductive disks are mounted on the shaft of the rotary element, so as to turn with the same, but are capable of a sliding movement, and an actuating-lever mounted on the frame of the motor permits them to be pressed toward the winding, progressively decreasing its resistance as the pressure increases.
The novel features of the invention will be more particularly pointed out hereinafter and will be definitely indicated in the claims.
In the accompanying drawings, which illustrate the invention, Figure 1 is a sectional view of a motor embodying myimprovements, parts being shown in elevation. Fig. 2 is a detached view showing the arrangement of the squirrelcage conductors at one end of the secondary element. Fig. 3 is a face view of a resistance-varying disk such as I prefer to employ. Fig. 4 is a detail showing the arrangement of the secondary conductors and their permanently-connected high-resistance path.
The frame of the motor may be of any usual or approved construction, comprising a primary and a secondary core composed of thin laminae of sheet-iron punched interiorly and eXteriorly to permit the windings to be nested in grooves in the core and mounted in supporting-frames. 1 and 2 represent these cores, and 3 the primary winding, which may be arranged as usual for the development of a progressive or rotary magnetic field and adapted for connection with an alternatingcurrent circuit. I form the secondary Winding by inserting in the grooves of the core bars of copper or other good conducting metal, as indicated at 4: P, 850. These bars are permanently connected together at one end of the secondary element by means of a conductive ring 5, permanently fixed in good electrical connection with the ends of the bars, as indicated in Figs. 1 and 2. The other ends of the secondary conductors are bent around the edge of the secondary element and all lie in the same plane. All of these are united electrically by a ring-conductor 6 of relatively high resistance to the conducting capacity of the secondary system. This ring-conductor may be let into grooves formed in the elbow of the conductors and connected by a good conductive joint or may be attached thereto, so as to form an effective electrical connection, in any suitable Way. I prefer to arrange the conductors so that their ends lie in groups terminating at different radial distances from the axis, as indicated in Fig. 4. On the shaft is mounted a group of dished conductive disks, as indicated at 7 in Fig. 1, permanently fixed to a sleeve 8, grooved or otherwise constructed, so as to be slid on the shaft to and from the conductors by means of a controlling-lever f), mounted upon or fixed to the frame of the motor. These disks constitute a low-resistance connecting device for the armature-00nductors, and they are dished with dilferent degrees of curvature, as indicated in Fig. 1, so that their peripheries lie when not strained at different radial distances from the center of the secondary element. The disks are radially slitted, as indicated in Fig. 3, so as to provide a plurality of peripheral elastic tongues or fingers capable of being straightened orfiattened out under a thrust toward the secondary element imparted by the lever 9. The dotted lines at 7 and 7", &c., indicate the normal positions of the edges of the several disksthat is to say, when they are not strained by compression.
In the normal position of adjustment when the motor is starting the lever is shifted so as to hold the group of disks out of conductive relation to the secondary Winding. In this condition of adjustment the several bars composing the squirrel-cage winding have a com mon metallic connection at one end to the good conducting-ring 5 and at the other end are connected together by a high-resistance ring 6. This ring is formed of such material or such cross-section as to afford the proper starting resistance for the motor. As the motor rises in speed and the slip becomes less relatively to the shifting or rotating magnetic field, the lever 9 may be adjusted so as to bring the cup-shaped disks progressively into engagement with the free ends of the conductors forming the secondary winding, and as these disks are shifted closer to the Winding the resistance gradually decreases by a progressively-increasing num ber of the disks being brought into engaging relation with the group of conductors whose terminals lie nearest the center of the secondary element, and a further decrease of resistance is afterward produced by cutting in a range or group of conductors or more than one range, if desired, lying farther from the center. Thus by varying the angle of the controllinglever any desired resistance and any desired torque may be efiected. The lever may be locked in a number of different positions of adjustment by pressing it into one of the notches in a serrated bracket 10 and held in its position of maximum torque by a toggle 11.
While I have illustrated and described in this case a novel form of low-resistance connecting device for short-circuiting the highresistance connection at the ends of the armature-conductors, and while this device constitutes one of the features of my present invention, it is evident that in its broader aspect my invention is not limited thereto, but that I may employ any suitable means for successively connecting the armatureconductors in different groups in order to reduce the effective resistance of the squirrelcage winding. Moreover, it is to be understood that in some cases it may be sufficient to so arrange the terminals of the armatureconductors on the face of the secondary element that the low-resistance device will simultaneously connect all of the conductors, and such an arrangement I aim to cover in the claims hereto appended.
What I claim as new, and desire to secure by Letters Patent of the United States, is
1. An induction-motor provided with a revolving secondary element having a squirrelcage winding, a high-resistance connection uniting the conductors of the squirrel-cage at one end, terminals connected to said conductors and located on the face of the secondary element, and a low-resistance connecting device mounted on the motor-shaft and adapted to be moved into engagement with said terminals.
2. An induction-motor having a squirrelcage winding on its secondary element, permanently connected by a low-resistance path at one end and by a high-resistance path at its other end, terminals, in conductive relation to the several conductors, on the face of the element at the high-resistance end, and a low-resistance coupler for said terminals.
3. An induction-motor provided on its secondary element with a squirrel-cage winding, the conductors of which are permanently connected by a good conductive path at one end, and are bent parallel to the face of the element at the other end so as to constitute terminals therefor, a conducting-ring of high resistance permanently connected to the conductors at the latter end of the element, and a low-resistance connecting device movable to and from the face of the movable element during its rotation, and adapted to engage the said terminals.
4. An induction-motor having a revolving secondary winding provided with a plurality of terminals and a radially-expansible coupler movable with the winding, adjustable to and from it to vary the resistance of the winding.
5. An induction-motor having a squirrelcage winding on its secondary member provided with groups of terminals, a permanent high-resistance connection to all of said conductors, and a coupling device for progressively coupling the groups on short circuit to vary the torque.
6. An induction-motor having a squirrelcage winding on its secondary element, and means for coupling the conductors in groups to vary the resistance during the operation of the motor.
7. An induction-motor having a revolving secondary element provided with a squirrelcage Winding, a radially-expansible cup-contact in operative relation thereto, and means for expanding the contact to couple the conductors and vary the resistance of the winding.
8. An induction-motor having a revolving secondary element provided with a squirrelcage winding, a series of terminals therefor on the face of the element arranged in groups at different radial positions, an elastic lowresistance coupler, and means for spreading it radially to progressively lower the resistance.
9. An induction-motor having a revolving secondary element provided with a squirrelcage winding, terminals, for all of the conductors of the squirrel-cage, on the face of the element, and a plurality of radially-expansible couplers adapted to be brought successively into engagement with the terminals to vary the resistance of the winding.
10. Aninduction-motorhavinga secondary element provided with a squirrel-cage winding permanently closed by a high resistance, a plurality of conductor-terminals on the face of the secondary element, a cup-shaped elastic coupler, and a lever for shifting it to crossconnect the terminals to provide a low resistance when the motor rises in speed.
11. An induction-motor having a movable secondary element, terminals for the winding of said element to vary its resistance, an elastic coupler to connect the terminals in different relations, a controlling device on a stationary part of the motor to adjust the coupler, and a lock to secure it in place when adjusted.
12. In an alternating-current induction- -Inotor,a squirrel-cage armature-Winding comprising a plurality of groups of conductors, a high-resistance connection uniting all of said conductors, and means for successively connecting the conductors of the several groups by a low-resistance connection.
13. In an alternating-current inductionm otor,a squirrel-cage armature-winding,having its conductors united at one end by a high-resistance connection, and means for making a low-resistance connection, first between a portion only of said conductors, and thereafter between all of said conductors.
14. In an alternating-current inductionmotor, a squirrel-cage armature-Winding having its conductors united at one end by a high-resistance connection, and means for making a low-resistance connection, first between alternate conductors and thereafter between the remaining conductors of the said squirrel-cage winding.
15. In an alternating-current inductionmotor,a squirrel-cage armature-winding having its conductors united at one end by a high-resistance connection, and a low-resistance connecting device having a plurality of operative positions in one of which the said device operates to connect a portion only of said conductors, and in the other to connect the remaining conductors.
16. In an alternating-current induction-,
motor, a squirrel-cage armature-windinghaving its conductors united at one end by a high-resistance connection, and a low-resistance connecting device having a plurality of operative positions in one of which the said device operates to connect together certain of said conductors, and in another to connect together other conductors of the said Winding. In witness whereof I have hereunto set my hand this 20th day of March, 1900.
CHARLES I. STEINMETZ.
BENJAMIN B. HULL, lVIABEL E. JAconsoN.