US1269152A - Single-phase motor. - Google Patents

Description

' J. BECKER.

SINGLE PHASE MOTOR.

APPLICATION FILED AUG.24. 1914. v 1,269,152. Patented Jun@ 11, 1918r 4 SHEETSf-SHEET l.

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SINGLE PHASE MOTOR.

APPLflcATloN FILED AuG.24, 19:4.

Patented June 11, 1,918`

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I. BECKER.

SINGLE PHASE MOTOR. APPLICATION HLD Aus.24. 1914;

Patented J une 11, 1918.

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SINGLE PHASE MOTOR.

APPLICATION FILED Aus.24, 1914.

1,269,1 52. Patented June 11, 19m

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JULIUS BECKER, OF RACINE, WISCONSIN.

SINGLE-PHASE MOTOR.

Specication of Letters Intent.

Patented June 11, 1918.

Application filed August 24, 1914. Serial No. 858,228.

To all whom t may concern:

Be it known that I, J'ULiUs BECKER, a subject of the Confederation of Switzerland, and a resident of Racine, Racine county, "Wisconsin, have invented certain new and useful Improvements in Single-Phase M0- tors, of which the following is a specification.

The resent invention relates to improvements 1n single-phase motors, and has for its main object the provision of a construction such that the motor will be self-starting-that is, will commence to operate upon the application of the single-phase currentand suchthat in the starting operation the motor will not draw an undesirably large current from the line. That is, one of the objects is to so construct the motor that in the starting operation the motor will not draw an excessively large current, or a current of volume approximating twice the normal full load. At the same time it is an object to so construct the motor that it will develop a large torque or turning effort at the start. This featureis of peculiar desirability in a motor intended for use under conditions where the load is connected to the motor at the time the 'start is made, as, for example, in railway work.

Another object of the invention is to sd construct the motor that it will have a better regulation than the single-phase motor of usual construction-that is, will not fall ofi' excessively in speed between normal noload running speed and normal full-load running speed. One objection to sin lephase motors of usual construction is t at they fall off seriously in speed as the load comes on, and one of the objects of the pres- 40 ent invention is to overcome this diiiiculty. In connection with the foregoin objects it is also an object to so construct tle motor that it will have a high power factor, so that the wattless current will not reach an abnormal igure. This has been a diiiiculty met with 1n most forms of single-phase motor heretofore developed andl at times has been a veryserious difiiculty. i

Still another object is to so construct the motor that the iron will be worked up to a high degree of usefulness, thereby increasing the weight eiciency, and ermitting the `notor to e made of comparatively small size and weight for a given output. One of the difficulties heretofore experienced in the design and construction of single-phase motors has been that the iron could not be used to its full limit, and that therefore it has been necessary to make the field of greater size than is the case with polyphase motors. This difficulty I have largely overcome in the present case in the manner to be presently described. Y

Still another object is to so construct the motor that it may be reversed at will, thereby permitting the operator to determine the direction of -rotation at the start and to reverse the direction at will.

Other objects will appear from a detailed description of the invention, which consists in the features of construction, and the combinations of parts hereinafter described and claimed.

Referring tothe drawings:

Figure l shows diagrammatically a four pole single-phase motor having applied thereto three short-circuited windings at various phase relationships or positions, each of said short-circuited or auxiliary windings being provided with a sin le turn, and the stator being further provi ed with two sets of such auxiliary windings so that the dixction of rotation can be controlled at w1 Fig. 2 shows an arrangement similar to that of Fig. 1, with the exception that each coil of the auxiliary windings is provided with a plurality of turns, as might be the case, for example, when the construction were to be used in a motor of comparatively large size;

Fig. 3 shows a section through one form of stator embodying the features of my 1nvention, the auxiliary windings placed in tunnels between the usual slots which accommodate the power windings;

Fig. 4 shows a section similar to -that of Fig. 3, with the exception that the tunnels for the accommodation of the auxiliary windings are elongated instead of being cir- 100 Fig. 7 shows a'view similar to that of being Figs. 3 and 4, the auxiliary windings in the present case being placedv in the same slots or tunnels which accommodate the power windings;

Fig. 8 shows a view similar to that of Fig. 7, with the exception that in the present case the slots or tunnels which carry the auxiliary windings are placed closer together than those which do not carry such windings;

Fig. 9 shows an enlarged view of one of the slots or tunnels of the arrangements shown in Figs. 7 and 8;

Fig. 10 shows an enlarged detail View of a desirable form of connection between the short-circuiting bar of the squirrel-cage rotor winding and the bar conductors of the same being taken on the line lil-l0 of Fig. 7, looking in the direction of the arrows; and

Fig. 11 shows diagrammatically the general relationships existing between the currents in the power and in the auxiliary.

windings, and shows how currents out of phase from the currents in the power coils are induced in the auxiliary windings, and how these currents which are out of phase from the main power current may beso related as to generate or produce a rotating field, even during the starting operation.

In carrying into edect the features of the present invention, I prefer to mount or build windings on the stator or stationary element intermediate the power windings prope which intermediate windings are so relate to the power windings proper and to the rotating element or rotor, that they will have induced in them currents of phase relationship diii'ering from, but bearing a desired relationship to, the currents in the power windings' proper. By so relating these auxiliary windings to the' power windings, they will have generated in them currents of such phase relationshipto those in the power windings proper that a rotating magnetic field will be produced. Where in the speciication and claims I use the term power windings or po'wer windings proper, it will be understood that I contemplate windings on the stator which carry the main current delivered from the line. Also where in the specification and claims I use the terms auxiliary windings or short- Vcircuited windings, it will be understood that I contemplate the auxiliary windings` to be presently described in detail, inasmuch as these auxiliary windings serve not only to provide the rotating field for starting purposes, but also serve to improve the normal operations or running of the machine.

Referring now to the diagram shown in Fig. l, the numeral 15 designates the power winding. In each of the several gures I have illustrated the features of my invention as applied to a :tour-pole construction, but

it is manifest that they may also be applied .to a construction including any number of poles. These four poles are designated by the numerals 16, 17, 18, and 19. Furthermore, I have illustrated the features of my invention as applied to a motor, the statorl side of` each of these poles I provide one or constitutes a closed circuit, electrically dis-` tinct from the power winding and from the other auxiliary windings, so that the currents existing in the several auxiliary windings will be distinct and separate from each other, although related magnetically.

In the arrangement shown in Fig. 2, the auxiliary windings are designated by the numerals 23, 24, and 25. In this case each auxiliary winding isprovided with two turns or conductors adjacent to each magnetic pole so that a greater magnetizing and inductive eiect is secured than in the arrangement shown in big. l.

In Figs. 3 to 9 inclusive, I have illustrated a number of constructions of stator' embodying the features of invention herein disclosed, which figures will be presently' described in detail. However, it will be understood at the present time that within the stator is mounted a rotor of suitable type of construction, as, for example, the squirrel cage type. In this type of rotor the conductor is short circuited and the alternating magnetic lield from the stator induces currents within the rotor windings, which cur rents are a function of the slip of the rotor and the frequency and yoltage of the stator.

The currents existing in the rotor winding or conductors will lag somewhat more than 90 degrees behind the current existing in the stator power winding, depending, among other things, upon the reactance of the rotor squirrel-cage circuit.

The currents existing in the rotor conductors will, in turn, react upon the auxiliary windings and generate electromotive forces in the same. These electroniotive windin forces will be approximately 90 degrees behind the currents existing in the rotor conductors. However, there will also be a direct induction from the main or power winding into the auxiliary windings, the electromotive force of which will lag behind the current existing in the main power winding an amount depending upon the several reactances of the circuits, and the amount of mechanical displacement of each auxiliary with respect to the power winding. is direct component of electromotive force will act with the component generated by the currents in the rotor, so that the net electromotive force in each auxiliary winding will be resultant of two components.

Referring to Fig'. l1, I have plotted diagraininatically curves showing in a general way the currents and electromotive forces existing in the main power winding, the rotor conductors, and one of the auxiliary windings. In thisease the current in the main power winding is designated by the numeral 25A. This current induces an electromotive force in the rotor conductors, which electromotive force lags approximately 90 degrees behind the 'current in the main ower winding. This electroinotive force is indicated by the curve 26. Owing to the reactance of the rotor electric circuit the current in the rotor conductors will lag behind the electromotive force in said conductors and may be indicated by the curve 27. Considering one of the auxiliary windings, and preferably considering the more simple arrangement illustrated in Fig. l, in which each coil of said winding is provided with a single turn, there will be induced in said winding a component of electromotive force by the current in the rotor conductors and which is indicated by the curve 27. This component of electromotive force will lag behind the current in the rotor and may be indicated by the curve 28. Owing to the self-induction of the rotor conductors which produces the lag between curves 26 and 27, the component of electro motive force 28 will be considerably more than 180 degrees behind the current in the main power winding.

The component of lectroniotive force generated in the auxiliary winding by direct inluence from the main power winding will lag behind the current existing in the power winding an amount dependent, among other things, upon the mechanical displacement .of the auxiliary winding under consideration, from the power winding, and may be designated by the curve 29 of Fig. 11. Obviously the net electromotive force existing in the auxiliary Winding which is available for the eneration yof current therein will be the resutant of electromotive forces represented by tlie curves 28 and 29 and which may be designed by the curve 30 of Fig. 11. The position of this curve with respect to the curve 25^ which indicates the current in the main power winding will depend upon the relative positions of the two curves 28 and 29, as well as their proportionate niagnitudes. The current in the auxiliary winding, of course, will lag behind the resultant electromotive force existing in it and may be designated by the curve 31.

The foregoing'analysis does not take dei nite account of the displacement of the auxiliary winding with respect to the main power winding along the face of the field magnet of the stator, and does not take into account the relative reactions between a plurality of separate sets of auxiliary windings, such as are shown in each of the several figures. These relative inter reactions are such that the phase relationships of the various auxiliary currents differ with respect to the current in the main power winding; thus auxiliary windings which lie with their turns closest to the centers of the power coils differ in phase relationship from the cui'- rent 4in the main power coils by an amount different from those currents in the remaining auxiliary windings. It is, therefore found by actual experience that a true rotating field is produced in the stator so that the turning effort exerted on the rotor is substantially the saine as that which is exerted on the rotor of a polyphase machine. The direction of thisl turning effort depends upon the relative positions of the auxiliary coils to one side or the other of the main power winding. It, therefore, follows that the direction or rotation both at the start and under normal running conditions can be controlled or determined by the location of the auxiliary windings. For example, in Fig. l, I have illustrated by means of the lines 31A, 32 and 33 a second set of auxiliary coils or windings which may be brought into action, if desired, by suitably connecting them and disconnecting the remaining coils. so doing the motor may be made reversible at will.

In the arrangement shown in Fig. 3 the auxilary turns are accommodated in tunnels 115 34 formed in the teeth between the power slots, the teeth being of uniform width throughout the entire periphery of the stator. This construction is suitable for use where each coil of the auxiliary winding constitutes a single turn. In the arrangements shown in Fig. 4, the auxiliary turns are accommodated in tunnels 35 also formed in the teeth between the adjacent power windings. This construction is. s uitable for use where each coil of the auxiliary winding consists of a plurality of turns either in the form of circular wires or bars 36, as shown in Fig. 5, or in the form of flat strips 37, as shown in Fig. 6. 130

ln some cases, it would be desirable to place the turns of the auxiliary windings in the same slots as those which accommodate the main power windings, and such arrangements are shown in Figs. 7, 8 and 9. Tn the arrangement shown in Fig. 7, all of the slots are of uniform width and the teeth between them are also of uniform width. The turns of the power winding are laid in the bottom portions of the slots, whereas the turns 38 of the auxiliary windings are laid in the top portions of the slots.

ln the arrangement shown in Fig. 8, the teeth 39 between those slots which accommodate the auxiliary windings are made of less width than theteeth 40 between those slots which do not accommodate the power windings. This arrangement is in general preferable to that in which' all' of the teeth are of uniform width for the reason1 that the existence of the currents into the auxiliary windings will modify or change the magnetic distribution so that a better operation and performance of the motor will be secured than where the teeth are all of uniform width. Tt will be noted in this connection that, in the arrangement shown in Figs. 3 and fi, the provision of individual tunnels for the accommodation vof the auxiliary windings will, in itself, cut down the amount of metal in the teeth in which these tunnels are formed, so that the net result in this case is similar to that of the arrangement shown in Fig'. 8.y

llt was previously shown that the resultant electromotive forces existing in the several auxiliary windings are functions of electromotive forces induced directly from the main power winding and from' the currents existing in the rotor.. ln some forms of construction it may be desirable to eliminate to a greater or less extent the one or the other of these influences, and, therefore, in Fig. 9 l have illustrated a magnetic'shield or the like 41 interposed. betwen the turns of the main power winding and those of the auxiliary winding. 'This arrangement may be particularly desirable for use in those constructions wherein the turns of the auxiliary winding are laid in the same slots with the turns of the main power winding. Ordinarily such a magnetic shield may take the form of a layerof magnetic steel laid between the windings, or it might take the form of an iron bridgeseparating two individual tunnels or slots in which the turns of the two windings are laid. a

ln Fig. 10, I have shown a suitable form of connection between the ends 42 of the bars of the squirrel cage and the encircling bar 43 which' joins together all of said bars and short circuits them. In this case, the bars .42 are flat and lie radially in the rotor, so that the rotation of the same will generate air currents for the purpose of cooling the machine to a greater extent than would otherwise be secured.A

\ It will frequently be found necessary to limit the volume of current owing in the auxiliary windings. This can be done by making said windings from a comparatively high resistance material, `such as iron or steel, or a suitable alloy, or the conductors lying in the tunnels or slots may be of copper with one or more sections of resistance material inserted in the circuit at a suitable point. lt may, however, be desirable to form the auxiliary windings of iron or steel, or other magnetic material, so as to make the magnetic conductivity as high as possible.

Experience has shown that it is preferable to use a plurality of sets of auxiliary windings, and ordinarily three sets of such windings will be found to give the best results. However, the exact number to be Iused in any given case will depend upon the various other factors entering into the motor construction, its size, frequency of the current on which itis to'be used, etc.

Machines embodying the features of invention herein disclosed will be found to have an unusually large torque at starting closely resembling a polyphase motor in this regard. Furthermore, the starting current, while generally larger than the corresponding running current, will not exceed the same by an undesirable large amount. Another feature which is disclosed in machines of this type is that they have an unusually good regulation; that is to say the change of speed between no load and full load is relatively small.

l claim:

l. ln a single-phase motor, the combination with a stator eld core, of conductors of a power winding embedded therein, con nections between said conductors for providing turns of power winding in the iield core suitably positioned therein for the generation ,of alternate north and south magnetic poles along the `face of the field core when the power winding is energized, groups of auxiliary. turns in the core intermediate 'turns of the power winding, each of said groups of auxiliary turns being suitably connected up to provide auxiliary sets of coils in the core displaced along the body thereof with respect to the coils of the power winding, land each of said sets of auxiliary coils having a different amount of displacement with respect to the power winding from the other sets of auxiliary coils, and e. rotor mounted within the stator core.

2. In' a single-phase motor, the combina- 4 tion with a stator field core, of a plurality of power coils embedded in the same and adapted to generate alternate north and south poles in the core, and agroup of auxiliary coils corresponding to each of the power recense coils, the auxiliary coils of each group being I angularly dis laced from correspondn power coils di erent an lar amounts, an

the auxiliary coils of t e various groups being connected u in sets, the auxiliary coils of each set being displaced from their respective power coils by equal angular amounts, for the purpose specified.

3. In a single hase motor, the combination of a stator eld core of a plurality of power coils embedded in the same and adapted to generate alternate north and south poles in the core, and a group of auxiliary turns on each side of each power coil, the auxiliary turns of each group being angufor connecting in series corresponding auxiliary turns o the several groups, for the purpose specified. A

JULIUS BECKER.

Witnesses:

THOMAS A. BANNING, G. E. DoWLE.

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