US1595550A - Variable-speed induction motor - Google Patents

Description

Aug. 10 1926. 1,595,550

D. e. HOWMARD VARIABLE SPEED INDUCTION MOTOR Filed Feb. 10. 1923 g s s t 1 A TTORNE V v Aug. 10 .1926. 1,595,550

D. G. HOWARD VARIABLE SPEED INDUCTION MOTOR Filed Feb. 10 1923 2 Sheets-Sheet 2 Z7 IIVVENTOR Qwid fiQowmov Patented Aug. 10, 1926. V

UNITED STATES v 1,595,550 PATENT OFFICE.

DAVID G. HOWARD, OF ANNAPOLIS,.MARYLAND.

VARIABLE-SPEED INDUCTION MOTOR.

Application filed February 10, 1923. Serial No. 618,216.

Some of the more important objects of the present invention are to enable the effective operation of an induction motor throughout a vconstantly and gradually variable range of speed and to accomplish this'with a simple, rugged and commercially practicable construction.

Other objects of the invention are to provide a variable speed motor having the desired characteristics mentioned, which will be readily susceptible of either arbitrary or automatic control.

One of the novel features of the invention enabling the attainment of the desired results is the mounting of the stator or primary windings at the opposite sides of or about the axisof the armature 1n such a way that they may be shifted toward and away from each other substantially radially of the armature so as to vary the point of imposition of the traveling magnetic field radially of the armature and hence apply theforce to the armature at different angular speeds.

Other novel features of the invention relate to the particular methods of interconnecting the stator windings grouped about the armature for the purpose of effecting their coooperative adjustment.

In the accompanying drawings forming.

part of this specification I have illustrated but a few examples of the different forms the invention may take and therefore Wish it understood that the structure may be modified in various respects without departing from the true spirit and scope of the invention as hereinafter defined and claimed.

In the drawings referred to, Figure 1 is a view in side elevation of one form of the motor.

Figure 2 is a top lan view of the same.

Figure 3 is an en arged detail illustrating diagrammatically the paths for the mag: netic flux.

Figure 4 is a side elevation illustrating another method of adjustably mounting the stator windings.

Fig. 4 illustrates a modification of the adjusting mechanism of Fig. 4.

Figures 5 and 6 are side and edge views respectively of another possible embodiment of the invention.

In the several forms of the invention herein illustrated, the armature is shown as of disc form, as indicated at 10, but this isby way of illustration as the rotor or secondary element may be of any usual or special design. The disc type of rotor, however, ofi'ers certain advantages in the matters of simplicity, relatively light weight and range of possible speed variat1ons and may be constructedwith or without conductors embedded therein, as found most advantageous.

The disc form'of rotor offers the further advantage that a number of such'rotors may be mounted tandem on the same shaft 11, spaced just far enough apart for the exciting windings therebetween, thus providing a maximum of power within a fairly compact machine.

The stator or primary windings are preferably constructed after the manner of electromagnets with plane polar surfaces to enable'the effective and ready adjustment of the same toward and away from the armature. These stator windings are designated 12 and may in themselves be of any usual or special form of distributed or salient pole windings such as are provided for polyphase induction motors,v transformers and the like. Thus in Figure 3 I have illustrated how with a multiple armature construction the exciting coils may be laid in slots in the faces of the magnet structures of the stator units divided and arranged to produce ten polar projections 13 on the end magnets.

At any instant ad'acent pairs of these polar projections will ave opposite polarit' but the polar projections of each pair will have like polarity. As illustrated in Fig. 3, each pair of polar projections on the end magnets will correspond to a single polar projection 14 on the inner magnet structures which are disposed between the discs, and will be placed and connected in a manner to produce a progressive magnetic flux cutting the rotor elements in the direction required to produce a turning movement on the armature. These inside magnets are shown as having five polar projections of alternate polarity and are connected and placed as shown to supplement the turning movement produced by the other stator magnets. In all cases the magnetic flux produced by the stator parts cuts the rotor discs in the progressive manner necessary for producing rotational torque of the roto discs about their axis.

Various means may be provided for supporting and adjusting the stator windings ut such means are preferably of such a nature as to efi'ect a continuously variable adjustment asdistinguished from a step-bystep adjustment so as to provide infinite variations in the speed.

In Figures 1, '2 and 3 I have indicated one simple form of supporting and adjusting means comprising for each rotor a pair of posts 16 having screwthreaded portions 17 engaged in screw seats or bosses 18 on the stator elements, thescrewthreads being arranged to operate in the turning of the posts to approach and separate the stator windings and the posts being connected to turn in unison as by means of suitable gearing 19.

The adjusting screws may be turned by hand, as by means of a handle 20 or power actuating means may be provided therefor such as a small electric motor indicated at 21 as having a pinion 22 in mesh with the gearing which connects the screws. Electromagnetic or solenoid action might also be used for efiecting the shifting, or pneumatic or other devices may be employed for the purpose as shown in Fig. 4

The stator windings are grouped about the armature and connected with a polyphase circuit in such a way as to produce the efi"ect of a progressive magnetic field traveling in the plane of the armature and I producing resultant rotation of the armature. By shifting the stator windings toward and away from each other it will be seen that the radius of this progressive magnetic field will.be reduced and increased and the force will thereby be applied to the armature at different distances from the center thereof and hence with lesser or greater leverage and at greater or less angular speeds. Thus by approaching and separating the stator elements both the speed and the torque of the armature are controlled and this through a relatively wide range. Also, the changes are effected gradually so that very fine adjustments can be made.

Where a multiple rotor construction is provided, the shifting means for the stators of the several rotors will preferably be interconnected as by gearing 30 so that the changing effects on all the rotors will be alike. In Figure 4 I have illustrated another method of mounting the stator windings at opposite sides of the armature axis including swinging arms 23 supporting the stator elements and pivoted at 24 with gear sectors 25 connecting them so that the arms will swing in unison toward and away from each other.

In Fig. 4 40 design-ates an actuator connected by a link 41 with a lever 42 aflixed tothe shaft 24. This actuator may be a solenoid and core or a cylinder and piston and may be either double or single acting. If single acting, a spring 43 may be provided to oppose its pull.

The stator elements may be placed at such an angle to the radius of'the disc that there occurs a radial thrust which may be utilized for automatic control. Furthermore, when placed normal to the radial elements of the disc, the stator is found to be acted upon by an appreciable outward thrust because of its tangential construction and mounting. The weight of the movable elements may be counterbalanced by suitable springs or weights as indicated at 26 in Figure 4, and the counterbalancing may be designed to cooperate with the outward thrust of the stator elements in effecting an automatic control of the machine, where such an automatic control is desirable, as in cases where constant torque or constant speed is required. This automatic control of speed and torque is possible as the outward thrust produced on the stator elements is proportional to the turning movement and, therefore, will vary with the load. As stated above, the outward thrust may be made positive or negative by changing the angle at which the stator elements are set.

By completely reversing the stator windings it will be seen that a reversal of the rotation may be effected. I have illustrated such a. possibility as this in Figures 5 and 6 where the stator elements are mounted on shafts 27 connected together by sprocket chain or other gearing 28 and operable by means of a handle 29 to simultaneously turn the windings to face the progressive magnetic field from one direction into a completely opposite direction. In efi'ecting this reversal it will be clear that as the stator elements are tilted or turned throughout the first half revolution the armature will be gradually slowed down and brought to a stop and will then in a continuation of the turning movement, be started in the reverse direction.

The reluctance of the magnetic circuit may be decreased if found desirable by the insertion of sections of magnetic material in the non-magnetic disc 10, which sections may be in the form of plugs 35 as indicated in Figure 1.

The invention, it will be seen, provides a polyphase induction motor having the rugged characteristics of the common squirrel cage type and for any given speed setting having operating characteristics very similar, but adapted in addition for infinite speed regulation within the limits of construction. Both rotor and stator are of comparativel simple construction and the rotor is relatively light and therefore adapted to be mounted directly upon the shaft or axle which it is to drive. The stator on the other hand maybe supported independently and even have a limited independent motion, since such independent motion will 'ferred to 1s have no harmful efiect on the rotor. Where large torque is re uired, as many of the disc armatures may e mounted on the shaft as found necessary. Because of the open construction both rotor and stator may be designed for heavy currents and because of the simple construction of the rotor, hi h 1 speed may be obtained-without danger, t e

induction motors and, therefore, will vary but a few percent when running as a motor at full load and when running as an induction generator.

What I claim is:

1. In a variable speed induction motor, a rotating armature,stator windings movably supported at opposite sides of the armature axis for imposing a rotating etic field on the armature and means for simul-.

taneously shifting said stator windings toward and away irom each other substantially radially of the armature.

2. In a variable speed induction motor, a

rotating armature, stator windingsmovably- 7 supported at opposite sides of the armature axis and interconnected to travel in opposite directions substantially radially of the armature and controlling means for effecting such radial adjustment of the stator wind- 1n In a variable speed induction motor, a rotating armature, stator windings movably supported at opposite sides of the armature ax1s and interconnected to travel in oppo- "site directions substantially radially of the armature and means for automatically effecting radial adjustment of the stator windingsin accordance with operating conditions i of the motor. slip can be made to approximate closely that obtained in the present commercial design of 4. In a variable speed polyphase induction motor, a rotor, stator elementsmovabl supported at opposite sides of the rotor axis and means for gradually shifting said stator elements toward and away from each other to thereby vary the angular s ed of the magnetic field imposed by said elements upon the rotor.- I

In witnesswhereo'f, I have hereunto set my hand this 24th day of October, 1922.

Davn) G. HOWARD.

Images