US1224895A - Induction-motor. - Google Patents

Description

F. BLANC.

INDUCTION MOTOR.

APPLICATION FILED JAN. 16. 1914.

Patented May 8, 1917 UNITED 'sfi ucrr s rAfrENT OFFICE.

FERDINAND BLANC, 0F CHARLOTTENBURG, GERMANY, ASSIGNOR TO SIEMENS- SCHUGKERTWERKE, G. M. B. H., OF BERLIN, GERMANY, A CORPORATION OF GERMANY.

INDUCTION-MOTOR.

Patented May 8, 1917.

Application filed January 16, 1914. Serial No. 812.460.

To all whom it may concern:

Be'it known that I, FERDINAND BLANC, a German citizen, and resident of Charlottenburg, near Berlin, Germany, have invented certain new and useful Improvements in Induction-Motors, of which the following is a specification.

My invention relates to induction motors, preferably of polyphase construction, having a short-circuited or squirrel-cage armature which is so constructed that the speed-torque characteristics of such a motor can be modified in order to meet particular service conditions especially those required for driving spinning machinery.

In general spinning machines are repeatedly started or stopped on one and the same day, and the individual spinning machines behave very different in practice as regards the requirement of starting torque. In order to secure the proper working conditions, in every case the start of the machinery must be made very smooth. In starting, one and the same spinning machine will sometimes behave in quite a different way, viz: it will start more sluggish in the morning when it is set in operation than during the course of the day after it I has been running one or several times. Also during summer time or in case for other reasons the room temperature is relatively high, the machines will start easier than during winter or at low temperature. is therefore desirable to be able to start the electric driving motors for the spinning machines with a torque which is adjustable within certain limits. For three-phase induction motors, as ordinarily employed in the present case, an adjustment of the starting torque of the motor upon the temporary load or the mechanical resistance of the spinning machine at starting is only made possible by regulating the short-circuit currents.

In order to obtain a smooth starting with an induction motor having a short-circuited armature for driving spinning machines, an idle armature has been provided on either .side of the working armature separately therefrom, which has the purpose to decrease the magnetic flux passing into the rotor by deflecting the flux generated in the stator. For regulating the flux passing through the working armature, and varying the starting torque the idle armatures are made adjustable to be either in direct magnetic contact with tho armature or in a greater or smaller distance therefrom.

The primary object of my present invention is to obtain in a simple and more per feet manner a smooth starting of the motor by having the ordinarily employed shortclrcuit rings of the squirrel-cage winding of the armature surrounded by 'magnetizable bodies either permanently or only temporarily during the starting. The decrease of the starting torque in this case is due to the phase-displacement to which the rotor currents aresubject in generating a new field independently from the stator field in the magnetizable ring. Another known construction consists therein that the shortcircuit rings, the iron surrounding the same and two further rings form transformers proper whereby the reverse effect, that is a high starting torque, is obtained. This latter construction of course is not related to my present invention.

My invention will be more fully understoodby reference to the accompanying drawing which shows in longitudinal sections four modes of carrying my invention into effect. In brief Figure 1 shows a construction having a magnetizable ring fixed upon the rotor with slots which is moved to and from the armature according to the working conditions of the motor. Fig. 2 shows a similar construction by which said magnetizable ring is moved by means of a centrifugal device, Fig. 3 a construction in which said ring of magnetizable material is fixed with respect to the bearing of the motor, and Fig. 4 a construction similar to that of Fig. 3 having an additional circular groove on said ring by means of which said ring may be adjusted by an adjusting device such as a lever, spindle or the like. Referring now more particularly to the drawing a is the stator, and b the rotor of my motor, and c is the axle of said rotor 5. In Fig. 1 a magnetizable ring f is fixed upon the rotor. This magnetizable rim is provided with slots 9 through which conductors c lead to the rings d. Another magnetizable ring 71, is mounted upon the axle 0 in a manner to be adjustable within certain limits in axial direction. the adjustment being secured by means of a key-way 2' which positively limits the motion. A helical spring j is provided between the body of' the rotor and the magnetizable ring it tending to move the latter away from the former.

If the motor is either at rest or working at normal speed of rotation. the ring h is 5 kept away from the ring, f by means of the spring 7' and will be pressed against the collar 70. If the motor is started the ring it by the magnetic action caused by the current pulsating in the ring, (I will be attracted and compress the spring j and come into a position as indicated in Fig. 1, namely surrounding ring-like the short-circuit ring (Z and forming with the fixed ring a good magnetic circuit. In this position of the ring it the self-induction in the short-circuit ring (Z will be a maximum and. accordinglj, the starting! torque of the motor will reach the desired minimum value. The more the motor is accelerating the more the, currents in the short-circuit ring (Z will be weakened, so that the spring can again gradually press the ring it backward and if the motor has reached its full speed of r0- tation the ring it also is abutting against the collar k.

Such adjustable ring it can be provided at both ends of. the motor arn'iature for either short-circuit ring thereof; also the rings it may he. so arranged that they are not positively moving with the motor; -furthermore they may be constantly kept fixed in any intermediate position. in order to obtain. the proper starting cl'iaracteristics for any individual machine which is driven from the motor.

The two rings f and it are advantageously subdivided by a number of radial cuts, or they may be composed of a number of segments which are insulated from each other.

In the construction of Fig. 2 the ring it is positioned during the standstill of the motor at a minimum distance from the an mature, and will be drawn away therefrom by the centrifugal force, exerted by the weights Z of the centrifugal device against the action of a spring at to an extent as the motor is accelerating. These weights mav be pivotally connected with the one end or guide-bars 0, the other ends of which are pivoted to the ring '1 mounted fixedly upon the axle 0 and to the hub of the movable ring it. Screws g or similar devices may serve to adjust the ring it to the proper initial position in order to adapt the starting torque to an individual case, as desired In Fig. 3 the ring it is mounted upon a sleeves of the bearing and does therefore not participate in the rotation of the m0-' tor.- In this construction the magnetizable ring f is substituted by the laminated iron of the rotor 71 and its disks. The operation of this construction will be the same as that of the construction shown in Fig. 1.

In another construction shown in Fig. the ring h is also kept in a fixed position and mounted upon a sleeve of the hen ing. For adjusting the ring ill a circula groovc't is provided around the hub or central part of said ring. A. ring-shaped body fits into the groove Z, said ring body being. made adjustable in axial direction by incans oi: the lever n which is pivoted at w and con nected to said ring it by means at the pin c which may slide relatively to said lever in a slot 1/ thereof. This lever now may be adjusted as desired to bring the magnetisable ring it into any position with regard to the armature of the motor, that is to say, in a shorter or greater distance ther i n, to meet the particular ioa liaracterictics ot' the driven machinery. l have also shown a locking device for locking, the lever o in a desired position. said locking device being represented in the drawing by the circuiar rack having its center at w, upon which by means of the pawl 10 and the thumb lever 11 the lever u may be fixed in any desired position. The ring it may also be made adjustable by a number o'lf other construct-ions. for instance it may be made to rotate upon the bearing sleeve in a thread of any desired gradient. so that by rotating the ring the desired distance between the same and the rotor may be adjusted.

In the constructions of I} and l the armature conductors are positioned in deep slots of the armature which do not contain. anv electrically or magnetically activoi'mrteriai. In case of rotors according to this construction the adjustable ring 72 serves only for the fine adjustment of the starting torque. The rings in the construction according to Figs. 1 and 2 may also be omitted and screws or similar means for adjustment may also be employed in tl: constructions of Figs. 1, 2 and i.

Having thusde, "ihed my invention I claim as new and desire to secure by Let ters Patent of the United States- 1. In an induction motor of polyphasc construction the combination of an armature having a squirrelscage wii'iding; the electrical resistance of said winding beinq such as to give a strong starting torque, and means, comprising a movable magneti h e ring partially surrounding a shmt-circutt ring of said. winding, for increasing only the reactance of said windin 2. In an induction motor of polyphase construction the combination of an armature having asquirrel-cage winding. the electrical resistance of said winding being such as to give a strong starting torque and means, comprising a movable magnetizable ring divided into a plurality of segments individually surrounding a short-circuit ring of said winding, for increasing only the reactance of said winding.

3. In an induction motor f polyphase construction the combination of an arrnat-ur having a squirrebcage winding, the electrical resistance of said winding being such to give a strong starting torque, means co1nprising a movable magnetizable ring partially surrounding a short-circuit ring of said winding for increasing only the reactance ot said winding, and in ans tor enlarging the distance between said short-circuit ring and said magnetizable ring with increasing speed oi? said motor.

4. in an induction motor of poiypiiase construction the combination of an armature having a squirrel-cage winding the electrical resistance of said Winding being such as give a strong starting torque, means comprising a movable magnetizable ring divided into a plurality of segments individually surrounding a short-circuit ring oi said winding, for increasing only the reaittance of said winding, and means for enlarging the distance between said short-circuit ring and said inagnetizable ring with increasing speed of said motor.

5. In an induction motor of poypliase construction the combination oi an armature having a squirrel-cage Winding, the electrical resistance of said Winding being such as to give a strong starting torque, means comprising a movable magnetizable rine' partially surrounding a short-circuit ring 02 said winding, for increasing only the reactance oi said winding and a spring being under tension at the starting period, said spring being adapted to-enlarge the distance between said short-circuit ring and said magnctizable ring with increasing speed of said motor.

(3 In an induction motor of polyphase construction the combination of an armature having a squirrel-cage winding, the electrical resistance of said winding being such as to give a strong starting torque, means com-4 prising a movable niagnetizable ring divided into a plurality of segments individually surrounding a shortcircuit ring of said windin for increasing only the reactance of said winding, and a spring being under tension at the starting period, said spring being adapted to enlarge the distance between said short-circuit ring and said niagnetizable ring with increasing speed of said motorl in witness whereof I have hereunto set my signature in the presence of two subscribing Witnesses.

FERDINr N D BLANC.

Yr itnesses: I

t foLnnMAn HaUr'r, Hnsnr Slasrnn.

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