US3610979A

US3610979A - Alternator having stationary primary and secondary windings

Info

Publication number: US3610979A
Application number: US868527A
Authority: US
Inventors: Serge Thomas
Original assignee: S E V MOBROLA
Current assignee: S E V MOBROLA
Priority date: 1968-10-31
Filing date: 1969-10-22
Publication date: 1971-10-05
Anticipated expiration: 1988-10-05
Also published as: NL151580B; DE1953642A1; DE1953642C3; GB1246065A; JPS5420642B1; NL6915828A; SE373242B; BE741106A; DE1953642B2

Abstract

An alternator comprises stationary primary and secondary windings and a rotor of magnetic material. The rotor comprises two peripherally toothed cheek plates, the teeth on which project toward each other parallel to the axis of the rotor, with the teeth on one cheek plate opposite the spaces between the teeth on the other cheek plate. The windings for the rotor is supported by radial tabs extending through the gap between the teeth on the two cheek plates and the ends of the tabs extending into slots in the stator.

Description

United States Patent [72] Inventor Serge Thomas Paris, France [21] Appl. No. 868,527

[22] Filed Oct. 22, 1969 [45] Patented Oct. 5, 1971 [73] Assignee Societe Anonyme Pour LEquipment Electrique Des Vehicles S.E.V. Marchal and S.E.V. Mobrola S.A. Issy Les Mauleneaux, France [32] Priority Oct. 31, 1968, May 13, 1969, May 16,

1969, Aug. 14, 1969 [3 3] France [31] 172,096, 6,915,370, 6,915,850 and [54] ALTERNATOR HAVING STATIONARY PRIMARY AND SECONDARY WINDINGS 33 Claims, 40 Drawing Figs.

[52] U.S.Cl 310/168, 310/263 [51] Int. Cl ..1'102k 19/24 50 Field ofsearchm.

[56] References Cited UNITED STATES PATENTS 2,073,760 3/1937 Schov 310/168 FOREIGN PATENTS 172,903 7/1965 U.S.S.R. 310/168 Primary Examiner-D. X. Sliney I Attorney-Holcombe, Wetherill & Brisebois ABSTRACT: An alternator comprises stationary primary and secondary windings and a rotor of magnetic material. The rotor comprises two peripherally toothed cheek plates, the teeth on which project toward each other parallel to the axis of the rotor, with the teeth on one cheek plate opposite the spaces between the teeth on the other cheek plate. The windings for the rotor is supported by radial tabs extending through the gap between the teeth on the two cheek plates and the ends of the tabs extending into slots in the stator.

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SHEET 130$ 13 ALTERNATOR HAVING STATIONARY PRIMARY AND SECONDARY WINDINGS BACKGROUND OF THE INVENTION In a rotating electrical machine operating on alternating current the rotor and the stator each comprise a winding and the rotor winding is commonly connected to the external circuit through a collector or by means of slip rings which cooperate with brushes. In the case of alternators, and particularly in the case of low power altemators adapted to be used in automotive vehicles, the rotor carries the primary coil and the stator the secondary coil, and the rotor is supplied as indicated above. It is clear that the need to use a slip ring and brushes offers an important suggestion for the construction of altemators, both with respect to an increase in the cost and with respect to wear during the course of use and the maintenance required to keep the brush in satisfactory contact with the collector.

SUMMARY OF THE INVENTION It is the object of the present invention to provide a rotary machine comprising a stator of a conventional type and a rotor in which the winding is not supplied through a collector or through brushes cooperating with rings. The substantial advantage of such a machine resides in the fact that the only maintenance required is that of the rotor bearing and that the machine may operate without inconvenience in dusty or greasy environments.

The present invention relates to a new article of manufacture which consists of a rotating electrical machine and in particular to a low power alternator adapted to supply automotive vehicles. This machine comprises a stator having conventional slots equipped with a winding, and a rotor comprising two cheek plates mounted on the same axis and a coaxial magnetic core positioned between the two cheek plates made of a magnetic material, each of which carries peripheral spaced teeth which are substantially parallel to the axis of the rotor. The teeth on one of the cheek plates are positioned opposite the spaces between the teeth of the other cheek plate. This machine is essentially characterized by the fact that, in the first place, there is a space between the plane in which all the ends of the teeth of one of the cheek plates and the plane in which all of the ends of the teeth of the other end member are located. In the second place, the rotor winding which is positioned between these two cheek plates and surrounds the magnetic core is supported by a cover which is fastened to the stator by means of members having a thickness less than the space between the planes in which the ends of the teeth of the cheek plates of the rotor are located.

In a preferred embodiment of the invention, the two cheek plates are identical and their teeth are trapezoidal in shape, as are the spaces which separate two consecutive teeth.

The cover of the rotor winding comprises tabs which are preferably radially positioned and regularly spaced about the periphery of the winding.

It will be appreciated that the material used to make the cover for the rotor coil is sufficiently rigid at the temperatures reached during the operation of the machine to avoid vibration of the rotor winding during the operation of the machine, which vibration might bring the cover of the winding into contact with some part of the cheek plates of the rotor. In order to reduce the vibrations of the rotor winding, the fastening tabs are provided with ribs which make it possible to increase the crosssectional area of the connectionbetween the tabs and the cover of the winding itself.

For the same purpose, to the extent possible, the mass of the rotor winding suspended from the stator is limited. In order to do this ribbons of anodizedaluminum may be used in place of copper wires. 4

It is obvious that, in such a machine, a compromise mustbe made between the minimum thickness required to adequately attach the rotor winding to the stator, and the maximum allowable space between the planes of the ends of the teeth on the end members of the rotor, if the rotating machine is to have an adequate output. In effect, the efficiency of this machine is dependent on the shape of its teeth and the fact that there are no overlapping teeth as is the case in a machine of a conventional type is a disadvantage. However, the advantages of strength and endurance which result from the arrangement according to the invention compensate for the slight decrease in its other desirable characteristics. The shapes of the teeth on each of the two cheek plates may also be suitably varied, and particularly the angle formed by the two nonparallel sides of these teeth, so as to obtain, in the case of an alternator, a current having a sufficiently high voltage without undesirable harmonics.

In a first type of construction, the tabs on the cover may terminate made in prongs or hooks which fit slidably into certain of the slots in the stator.

An electrical machine according to the invention utilizing this type of construction may be advantageously assembled in the following manner. Taking first the stator winding and the rotor winding with its tab-carrying cover, the prongs at the ends of the tabs on the rotor cover are slid into certain of the notches in the stator until they reach a predetermined position with respect to one of the lateral faces of the stator which is indicated by one or more axial positioning stops or wedges. The stator winding is then impregnated with a synthetic resin so as to attach the different wires of this winding and the prongs which have already been mentioned firmly together. The two cheek plates of the rotor which carries the central magnetic core are then put in place around the rotor winding which has been thus attached to the stator.

The axial shaft of the rotor is then inserted in the central bore in the cheek plates and the magnetic core and the rotor is positioned on the stator by means of an external frame carrying two rotary bearings which cooperate with the shaft of the rotor.

In order to facilitate the positioning of the prongs in the slots in the stator, these prongs may have a slightly trapezoidal section in an axial plane.

The first method of making this cover consists in making a molding about the winding, which molding may be provided with the tabs and prongs which are required. The molded rotor winding may be made of a plastic material such as NYLON and RILSAN, but may also be made of any other nonmagnetic material including a metallic material.

In a second method of manufacture the cover for the rotor winding is made of two identical circular halves which are attached to each other by engaging each tab on one half of the cover with a mating zone on a tab on the other half of the cover. The two parts of the cover according to this second method of manufacture may be made of a nonmagnetic metal, such as aluminum or an aluminum alloy.

In a first variation of this second method of manufacture the substantially radial tabs of each part of the cover are positioned at a slight angle with respect to a plane which is perpendicular to the axis of the box and which passes through the base of the tab in question. In this case the two parts of the cover are attached to each other, after engagement of the contact zone of each pair of associated tabs, by straightening these tabs so as to render them perpendicular to the axis of the cover. In this variation short connecting prongs are perpendicular to the tabs on the cover halves and become parallel to the axis of the box when the tabs are straightened.

In a second variation of this second embodiment of the invention the tabs are radial and perpendicular to the axis of the cover but comprise two contact zones at a slight angle to the median plane of the box. In this variation the two contact zones of the tabs of the two halves of the cover are brought into contact by a slight rotation of one of the tabs of the box with respect to the other, which rotation makes it possible to bring the prongs on each of the tabs into alignment with the prongs on the other half of. the box.

A third embodiment of the invention is essentially characterizedlby the fact that the cover for the rotor winding is made with the rotor. This ring carries a radial flange perpendicular to the axis of the rotor, which flange is radially notched to permit the passage of the wires for connecting the rotor winding. The radial tabs on the cover are attached to the cylindrical ring and carry prongs at their ends which are parallel to the axis of the cover.

The cover according to this third embodiment of the invention may advantageously be made of a nonmagnetic metal such as aluminum or an aluminum alloy. The radial tabs of the cover are connected to each other by rigid webs. The cylindrical ring is slotted in alignment with the radial notches in the flange of the cover and the web between the adjacent tabs encircling this area is grooved to admit the wires connecting the winding of the rotor. The tabs of the cover are provided with reinforcing webs which are parallel to the axis of the box.

In a fourth embodiment of the invention the rotary electrical machine is essentially characterized by the fact that the cover for the rotor winding is made in two parts, which are preferably identical, each part comprising radial tabs and each tab terminating in a prong parallel to the axis of the cover, the middle part of said prong being attached to the corresponding tab. These prongs may he slid into certain slots in the stator, the tabs on one half of the cover being angularly spaced with respect to the tabs of the other half of the cover.

In a fifth embodiment of the invention the rotary electrical machine is essentially characterized by the fact that the cover for the rotor winding is made from several discrete arcuate sectors, each having a U-shaped section, the depth of which is substantially equal to the thickness of the winding. These sectors are preferably identical and are mounted alternately on opposite sides of the winding and each is provided with at least one radial tab on its outer circumference in approximately its median plane. Each tab is provided with a prong parallel to the axis of the corresponding sector and preferably connected at its midpoint to the tab which carries it. The prongs may be slid into certain of the slots in the stator so that the tabs become positioned in the median plane of the stator.

In a sixth embodiment of the invention the machine is essentially characterized by the fact that the cover for the rotor winding is made of a circular casing having a U-shaped section substantially equal in depth to the axial thickness of the winding. The rotor winding is positioned inside the annular opening defined by this cover and the cover carries radial tabs on its outer wall, each of which tabs is provided with a prong parallel to the axis of the cover. These prongs may be slid into certain of the slots in the stator so that the tabs become positioned substantially in the median plane of the stator.

In a seventh embodiment of the invention the machine is essentially characterized by the fact that the cover for the rotor winding is made of several strips which encircle the ring constituting the winding in planes which are axial to said winding. The ends of these strips are folded perpendicularly to the outer surface of the ring formed by the winding near the median plane thereof so as to form a radial tab. These tabs are bent at right angles to produce at each end of the strip a hook or prong parallel to the axis of the winding which may be slid into certain slots in the stator.

These strips are preferably made from a sheet of nonmagnetic metal. The bent ends of the tabs may, in a first variation, be situated on opposite sides of the median plane of the winding, each strip being independent on the adjacent strip. In a second variation the tabs may pass through the median plane of the winding and form the fastening by crossing the ends of each strip. Each strip is also independent of the others. In a third variation the strips may be connected to each other by circumferential connecting means. The fastening tips may correspond to those of either of the two previous variations just mentioned. In a fourth variation the strips may be directly molded around the section of the ring which forms the windi g. this molding being carried out by using a readily fusible material having good heat conducting properties.

In an eighth embodiment of the invention the machine is essentially characterized by the fact that the rotor winding is made in two halves wound in the same direction. The cover for these two halvescomprises, on the one hand, a central sheet carrying peripheral fastening tabs which cooperate with the stator, and on the other hand, on each side of said sheet, a hollow annular seat containing one of the aforesaid winding halves.

The central sheet of the cover for the two winding halves may advantageously be made by cutting out and stamping a sheet of a preferably nonmagnetic metal. It may be also made by molding a preferably nonmagnetic material which is a good conductor of heat. In a first variation the fasteners at the periphery of the central sheet consist of radially projecting tabs, each carrying at its end a prong parallel to the axis of the winding cover. In a second variation the radial tab carries at each end a prong formed by bending it at right angles to the main tab, the successive tabs carrying prongs being positioned on opposite sides of the central web.

In the second type of construction, the means by which the cover for the rotor winding is attached to the stator may not comprise any prongs, but may consist simply of tabs which are inserted into the slots of the stator. The following embodiments represent this type ofattachment:

In a ninth embodiment of the invention the machine is essentially characterized by the fact that the rotor winding consists of a box made of one piece, or in two halves, which box carries on its external circumference near its median plane projections the width of which at their outer end is slightly greater than the distance which separates two successive pole shoes on the stator. These projections are arcuate at their central parts and are angularly spaced by a distance which is a multiple of the distance between the slots of the stator.

It should be noted that, in this ninth embodiment of the invention, the projections serve the purpose of the fastening tabs and are not equipped with any prong or hook means. They are inserted in place by simply flattening the arcuate parts of the projections between the jaws of a press. This operation forces the ends of the projections to enter between the laminations of the stator adjacent the spaces which separate two successive pole shoes of the stator.

It should be further noted that a combination of the eighth and ninth embodiments may be made. In this case the fasteners on the central web of the cover of the eighth embodiment are projections which are arcuate at their central parts, the ends of said projections having a width slightly greater than the space between two successive pole shoes on the stator. These projections may be spaced one from the other by a distance which is a multiple of the space of the slots in the stator.

In a tenth embodiment of the invention the machine is essentially characterized by the fact that the cover of the rotor winding consists of two substantially identical halves which cooperate with a winding consisting of a single coil or of two coils, each cover half comprising in the zone at which it comes in contact with the other half a flat annular flange which is perpendicular to the axis of the cover and carries on its periphery, preferably regularly spaced, fastening tabs having a curved section. These curved tabs are so disposed that when the two box halves are assembled their concavities are opposite each other.

It should be noted that in this tenth embodiment the rotor winding is mounted in the stator by positioning that winding which, may consist of a single coil or two coils, in the seat which has been provided for its reception, by bringing together the flat annular parts of the two cover halves support ing said coil by sliding the curved tabs of the two halves placed one opposite the other inside certain of the slots in the stator and then squeezing the attaching tabs between the opposed jaws of a press to decrease or even eliminate by crushing the concavity of the attaching tabs. In the course of this action of the press the edges of the fastening tabs become anchored between the laminations which form the stator thus assuring a firm attachment of the half covers to the stator. It is clear that the width of the ends of the tabs, while curved, is slightly less than the width of the slots in the stator in order to permit the two half covers to be easily positioned in the stator by sliding the tabs into the slots. It is also clear that the angular distribution of the tabs of the two cover halves is identical and that the angular space between two successive tabs is a multiple of the polar pitch of the stator.

In an eleventh embodiment of the invention the machine is essentially characterized by the fact that the cover for the rotor winding is provided at its periphery with radially projecting fastening tabs which are spacedfrom each other by an angular distance which is a multiple of the polar pitch of the stator and have a width less than the width of the slots in said stator. These radial tabs come into abutment with an element which is fixed to the stator, which element has a base near the median plane of the stator, the radial tabs being retained in position against this abutment by a suitable wedge.

In a first variation of this eleventh embodiment of the invention the radial tabs on the cover for the rotor winding abut against a first series of wedges, which are preferably nonmagnetic, which have been seated in the stator slots by any appropriate means, and the radial tabs are held in position against these stops or wedges by means of a second series of wedges which block the zone of the slots through which the radial tab was slid to bring it up against the first series of stops. The stops or wedges may be held in position either by gluing them, or welding them, or by force fitting.

In a second variation of this eleventh embodiment of the invention the stator comprises among its stack of laminations one in which the slots have been less deeply cut. This lamination is near the middle of the stator. There is therefore inside at least some of the slots of the stator, a protuberance or ledge which is situated substantially in a median plane and may serve as a stop for the radial tabs of the cover for the rotor winding. The radial tabs may be held in position against this stop by means of wedges which may be force fitted or adhesively secured or soldered in place. Preferably the wedges are made of a nonmagnetic material. In a third variant of the eleventh embodiment the stator comprises in its stack of laminations, at least one in which the slots are so formed as to provide at one edge of the slots, in the zone forming a pole shoe, a recess having a depth less than the width of the pole shoe. This lamination is mounted near the median plane of the stator. The thickness of the lamination or laminations cut out in this manner is substantially equal to the thickness of the radial tabs of the cover for the rotor winding. Preferably the depth of the recesses in the median sheets of the stator is slightly greater than the width of the radial tabs of the cover for the rotor winding. In this variation the radial tabs are slid into certain of the slots in the stator until they come into alignment with the supplementary recesses in the median laminations of the stator. By rotary movement all the radial tabs are then introduced into these recesses so that the tabs are locked against axial movement. In order to hold the tabs in place wedges are then introduced into the slots and held in position by any suitable means, and in particular by force fitting, gluing or soldering. The wedges are preferably made of a nonmagnetic material.

It will be appreciated that all the embodiments which have thus far been described are particularly economical and that the covers enclosing the rotor windings are sufficiently rigid to prevent any vibration of the rotor winding during the operation of the rotating electrical machine.

It has also been noted that during the electromagnetic operation of the machine the inductive flux from one of the rotor teeth passes through the gap and enters the stator pole opposite thereto. It passes through the shoe of this pole toward the base of the pole, and then travels about the stator ring until it reaches the adjacent pole which it traverses from base to shoe, after which it crosses over the airgap and returns to the rotor through a rotor tooth adjacent to the original tooth but belonging to the'cheek plate of the rotor which does not carry the tooth from which it left.-

It follows that the path of the flux through the stator is oblique with respect to the radial plane and that this flux enters on the side of one of the lateral faces of the stator and leaves from the opposite lateral faces of the stator.

An advantageous embodiment of the invention utilizes the foregoing peculiarities with respect to the path of travel of the magnetic flux. It is accordingly the object of the present invention to provide as a new article of manufacture a rotary electrical machine of the above-described type which is essentially characterized by the fact that the stator poles have, in a plane perpendicular to the axis of the stator, a very decidedly trapezoidal shape, their shoe in the zone of the air cap being enlarged in a conventional manner but their base having a width between 40 percent and 70 percent of the width of the corresponding poles of a conventional type in a plane laterally limited by radial planes passing through the axis of the stator.

It is obvious that the reduction in thickness of the bases of the stator poles is limited in the first place by the magnetic properties of the material of which the stator is made and by those inherent in the general operation of the particular rotating electrical machine envisaged, and in the second place, by the mechanical strength which is necessary to ensure that the stator poles are not too fragile and will not be subject in operation to undesirable vibrations.

It has been found that by adopting a stator having poles of the above-described type the improvement in the electrical characteristics of the machine envisaged may be as great as about 15 percent. It should be noted that the arrangement according to the invention considerably increases the volume of the slots in the stator, and consequently the space available for the inductive winding. It follows from this arrangement that the machine may be made lighter than prior art machines having the same electrical characteristics.

The improvements obtained by adopting the arrangements according to the invention result from the fact that the magnetic flux, as has been indicated above, passes from a stator pole to an adjacent pole through a path which is oblique with respect to the median radial plane of the slot which separates the two stator poles in question. In effect, the flux enters a stator pole through a small zone at the surface of the shoe of the pole which zone is opposite the rotor tooth from which the inductive flux is received and consequently is positioned on one side of the median plane of the alternator, so that the tooth of the cheek plate of the rotor is necessarily situated on a single side of this plane, and provides between the two end members the space required for the members needed to attach the rotor winding. The flux which has thus entered the stator pole through one of the side faces of the stator must then leave the stator through an adjacent pole but in a zone of the pole which is placed on the other side of the median plane of the alternator so that the flux must return through a rotor tooth which belongs to the other end member of the rotor. It follows that, in the zones of the pole shoes of the rotor, the flux passes through only relatively small surfaces positioned near the lateral faces of the rotor. On the other hand, the passage of flux into the stator between two adjacent poles takes place in such a way as to spread the lines of flux inside of the annular stator ring which serves as a yoke. This spreading, which takes place in an axial direction with respect to the alternator, increases the zone through which the flux passes in the axial direction and thus makes it possible to narrow this passage perpendicularly of the axis without thereby limiting the flux by saturating the material.

In order that the invention may be better understood, several embodiments thereof will now be described purely by way of illustration and example, with reference to the accompanying drawings in which:

FIG. 1 is an axial sectional view through a first embodiment of the alternator according to the invention;

FIG. 2 is a detail view, also in axial section, showing how the rotor coil is attached to the stator in the machine according to FIG. 1;

FIG. 3 is a perspective exploded view showing the different components making up the alternator of FIG. 1;

FIG. 4 is a side view, partially in axial section, showing a cover made of two parts in accordance with the second embodiment of the invention;

FIG. 5 is a perspective exploded view showing the two components of the cover of FIG. 4 and the rotor winding which is to be mounted therebetween;

FIG. 6 shows schematically in section the first embodiment of the cover of FIG. 5, with the two parts thereof brought together;

FIG. 7 shows the cover of FIG. 6 after the two components have been fastened together;

FIG. 8 is a view taken perpendicularly with respect to the rotor axis of a second variation of the second embodiment of the rotor winding cover;

FIG. Q shows the cover of FIG. 8 after the two components of the cover have been brought together;

FIG. 10 is an elevational view showing a third embodiment of the cover for the rotor winding which has been hereinbefore described;

FIG. 11 is a sectional view taken along the line XI-XI of FIG. 10;

FIG. 12 is a perspective view showing a detail of the recess in the end member of the cover of FIG. 10 and the corresponding recesses in the cylindrical ring of this cover member;

FIG. 13 is a perspective view showing the two halves of a cover for the rotor winding according to the fourth embodiment of the invention;

FIG. I4 is an axial sectional view through an alternator according to the invention comprising a cover such as the one shown in FIG. 13;

FIG. 15 shows the components of a rotor winding cover according to the fifth embodiment of the invention;

FIG. 16 is an axial section through a rotor winding cover according to the sixth embodiment of the invention;

FIG. E7 is a partial perspective view of a rotor winding cover according to the first variation of the seventh embodiment of the above invention;

FIG. 18 is a schematic view showing in partial axial section a rotor winding cover according to the second variation of the seventh embodiment of the invention;

FIG. 19 is a perspective view showing, before assembly, a component designed to constitute a cover for the rotor winding according to the third variation of the seventh embodiment of the invention;

FIG. 20 is a schematic axial sectional view showing a rotor winding cover produced from the components shown on FIG. I9;

FIG. 21 is a perspective view showing a rotor winding cover according to the second variation of the eighth embodiment of the invention;

FIG. 22 is an axial section taken along the line XXIIXXII of the rotor winding cover of FIG. 21;

FIG. 23 is a perspective view showing two cover halves according to the ninth embodiment of a rotor winding cover according to the invention;

FIG. 24 is a schematic partial axial sectional view showing a rotary machine according to the invention in which the rotor winding cover of FIG. 23 is being mounted inside the stator;

FIG. 25 is a partial end view of the rotating machine according to FIG. 2 after the rotor winding cover has been put in place;

FIG. 26 is a schematic partial axial sectional view of a rotor winding cover combining the eighth and ninth embodiments of the invention;

FIG. 27 is a perspective view showing in detail the radial mounting tabs having a curved section carried by a rotor winding cover according to the tenth embodiment of the invention;

FIG. 28 is an axial sectional view showing a rotor winding cover according to FIG. 27 being mounted in a stator;

FIG. 29 is a top plan view showing the elements seen in FIG. 28;

FIG. 30 shows the position of the components seen in FIG. 29 after the jaws of the press have acted thereon;

FIG. 31 is a sectional view taken along the line XXXI- XXXI of FIG. 32 showing part of a rotating machine according to the invention which is equipped with a rotor winding cover according to the first variation of the eleventh embodiment of the invention;

FIG. 32 is a partial axial section taken along the line XXXIIXXXII of FIG. 31;

FIG. 33 is a partial axial section through a machine according to the second variation of the eleventh embodiment of the invention;

FIG. 34 is an end view showing part of a rotating machine according to the third variation of the eleventh embodiment of the invention;

FIG. 35 is a sectional view taken along the line XXXV- XXXV of FIG. 34;

FIG. 36 shows the components of FIG. 34 after the rotor winding cover has been mounted inside the stator;

FIG. 37 is an elevational view, with part of the casing broken away, showing an alternator having stator poles which have been modified in accordance with the invention;

FIG. 38 is a perspective view illustrating the path of travel of the inductive flux from one stator pole of the alternator of FIG. 37 to the adjacent stator pole;

FIG. 39 is a perspective view showing an alternator having stator poles in accordance with the invention; and

FIG. 40 is a perspective view showing a conventional alternator stator, for purposes of comparison.

Referring now to the drawings, and particularly to FIGS. 1 to 3, it will be seen that reference numeral 1 indicates the casing of an alternator comprising a stator 2 and a rotor 3. The rotor turns about the axis 4 which is supported in bearings 5 in the casing l.

The rotor consists of two identical cheek plates 6 centered on the shaft 4 and comprising rotor teeth 7 separated from each other by spaces 8. The teeth 7 of the two cheek plates 6 lie within a cylindrical locus encircling the shaft 4 of the rotor. The teeth on one of the cheek plates are positioned opposite the spaces between the teeth on the other cheek plate. The ends of the teeth 7 of the two cheek plates 6 lie in two parallel planes about 4 mm. apart. Between these cheek plates is a cylindrical magnetic core 9 which is coaxial with the rotor.

The winding 10 of the rotor in the annular volume defined by the cheek plates 6 and the core 9 is mounted. A thin layer of a synthetic resin such as RILSAN is molded onto this winding and reference numeral I1 indicates this layer. The thickness of this covering layer is about I to 2 mm. and it is provided with openings 12 on the two lateral surfaces of the winding, that is to say on those surfaces which face the cheek plates 6. The cover 11 carries tabs 13 which are about 2 mm. thick and project toward the stator in a plane perpendicular to the shaft of the rotor. There are six of these tabs regularly spaced around the winding 10. At the end of the tabs 13 are the prongs 14 which are substantially parallel to the shaft of the rotor. The prongs 14 have a transverse section which permits them to be inserted in the slots of the stator 2. Their longitudinal profile is trapezoidal in order to facilitate their insertion into these slots, as will be hereinafter described.

In the embodiment which has just been described the rotor has an external diameter of 89 mm., and each cheek plate 6 comprises six teeth regularly spaced about its periphery. The winding 10 of the rotor is made of copper wire 0.67 mm., in diameter and comprises 1,100 ampere turns. The alternator is designed to furnish three phase current. The stator has 36 slots, that is to say 12 slots per phase, and in each slot are 22 copper wires having a diameter of 0.85 mm. The gap between the rotor and stator is 0.3 mm., and the external diameter of the stator is I27 mm.

In order to assemble the various components of this alternator the winding I0 is first prepared and the cover II, together with the tabs I3 and the prongs I4, is molded onto the winding. It should be noted that the tabs 13 are connected to the prongs I4 on the one hand and to the cover of the winding 10 on the other hand by rigid reinforcing webs 15. The stator winding is then brought into position and the six prongs 14 are introduced into six slots in the stator which are spaced 60 from each other. The prongs are inserted between the pole shoes which partially close these notches and the stator winding which has already been put in place. This insertion is facilitated by the angular shape of the prongs 14. The tabs 13 are positioned at the proper point axially of the shaft of the alternator by bringing them up against a stop having a predetermined position with respect to one of the lateral surfaces of the stator. A synthetic resin is then spread over the stator winding and the prongs 14 to hold the wires of the winding and the prongs 14 together.

The magnetic core and the cheek plates 6 are then put in place with the cheek plates on opposite sides of the winding 10. The assembly is completed by centering the rotor in the stator by inserting the shaft 4 of the rotor, in the bearings in the casing 1.

Turning now to the electrical connections, it should be noted that the stator winding is connected to supply terminals or to a rectifier in a conventional manner and that the rotor winding is connected to two terminals mounted on the casing of the alternator through two wires which pass through the middle of one of the mounting tabs 13. This is done when the plastic material is molded onto the winding 10.

Such an alternator begins to supply current at about 1,000 rpm. and at about 5,000 rpm. will supply about 32 amperes at 14 volts after passage through a rectifier. In a conventional alternator having the same components, with a movable rotor winding positioned between the cheek plates with overlapping teeth, current generation will begin at about 1,000 rpm. and a rectified current of 42 amperes at 14 volts will be supplied at 5,000 rpm. it is obvious that the output of the machine according to the invention is slightly less than that of analogous altemators of a conventional type. However, the embodiment which has just been described has compensating advantages because of the fact that the rotor has neither a slip ring nor a commutator, with the rotor winding being supplied through the stator. This arrangement makes it possible to operate such an alternator in greasy or dusty atmospheres with much less attention to upkeep.

In the embodiments described and illustrated on FIGS. 4-40, the general characteristics of the alternator according to the invention are essentially the same. They will not, therefore, be redescribed in detail for each embodiment of the invention.

Referring now to FIG. 4, it will be seen that, in the second embodiment of the invention, the alternator comprises an outer casing 31 enclosing a stator 32 and a rotor 33. The rotor 33 turns about the shaft 34, and comprises two identical cheek plates 36 which are centered on the shaft 34. They are provided with peripheral teeth 37 separated by suitable spaces. The teeth 37 of the two cheek plates 36 are positioned in a substantially cylindrical locus coaxial with the axis 34 of the rotor. The teeth of one of these cheek plates are positioned opposite the spaces between the teeth of the other cheek plate. The ends of the teeth 37 of the cheek plates 36 are positioned in two parallel planes spaced about 4 mm. apart. Between the two cheek plates is a cylindrical magnetic core 39 which is coaxial with the rotor. The rotor winding 40 is positioned in the annular space defined by the cheek plates 36 and the core 39.

In this second embodiment, the Winding 40 is enclosed within a cover consisting of two identical parts 41. Each part 41 comprises a cylindrical ring 42 which is coaxial with the rotor.- At one side of this ring is an annular flange 43 perpendicular to the shaft of the rotor and attached to the ring 42. The ring 42 and the flange 43 are integral. At the side of the ring 42 remote from the flange 43 are the radial tabs 44 carrying prongs 45 at their free ends. The central portions of the tabs 44 are wider than the bases of these tabs. The prongs 45 are perpendicular to the tabs 44. In a first variation of this second embodiment, which is more particularly illustrated on FIGS. 5, 6 and 7, the enlarged portions of the tabs are at a slight angle to a plane perpendicular to the axis of the components of the cover 41 and passing through the base of the radial tab in question. When the winding 40 is mounted in the cover formed by the two parts 41 the winding is introduced between the two halves of the casing by inserting the tabs 44 on one half of the cover into the spaces which separate the tabs 44 on the other half of the cover. The two halves of the cover are then relatively rotated so as to bring the enlarged parts of the tabs 44 on one half into registration with those on the other half. The two halves of the cover 41 are then finally attached together by squeezing them together between the jaws of multiple pliers which act on opposite sides of the tabs 44. This operation is illustrated in FIG. 7. The action of the jaws 46a, 46b of the pliers make it possible to straighten the tabs 44 and render them exactly perpendicular to the common axis of the two halves of the cover. At this moment the prongs 45 are positioned in alignment with each other.

A second variation of this second embodiment of the invention is illustrated in FIGS. 8 and 9. In this second variation the enlarged areas on the tabs 44 are at an angle to the median plane of the cover perpendicular to the axis of the rotor, and the prongs 45, before mounting, are parallel to the axis of the two parts of the cover 41. At the moment at which these two cover halves are brought together the tabs of one half enter into the spaces between the tabs of the other half and one of the halves is then rotated so as to bring the enlarged portions of the tabs 44, which are designed to cooperate with each other, into contact. This rotation is continued until the prongs of the two tabs of each cooperating pair are brought into alignment. Because of the inclination of the enlarged portions relative to the median plane of the cover this rotation brings the two cover halves together so as to enclose the rotor winding therebetween.

It will be noted that, in the two variations which have just been described, the last step of mounting the winding 40 in its cover involves the tightening of the two halves 41 of the cover around the winding 40 so as to prevent this winding from moving relative to the cover.

When the winding 40 has been enclosed in the cover formed by its two halves 41, the cover is inserted into the stator by sliding the two prongs 45 into the slots of the stator which are adapted to receive them. It is obvious that the angular separation between the two successive radial tabs is a multiple of the angular separation between two successive stator poles.

When the winding 40 has been mounted in the stator by introducing the prongs 45 into the stator slots, the shaft 34 of the rotor is inserted into the center of the winding 40, the cheek plates 36 on opposite sides of this winding, and the core 39. Details of this mounting process have already been described.

FIGS. 10 to 12 illustrate a third embodiment of the invention. The cover shown is adapted for use in an alternator of the type which has already been generally described. Only the construction of the cover is different.

Referring now to FIGS. 10 to 12, it will be seen that, in this variation, the cover holding the winding 40 consists of an annular cylindrical ring 47 having the same axis as the winding 40. At one side of the ring 47 is a flange 48 which lies in a plane perpendicular to the axis of the winding 40 and of the rotor 33. The flange is in the form of a series of radial tabs 49 connected at one end by the ring 47 and at the other end by a connecting ring 50. The spaces 51 which separate two successive tabs 49 permit the ventilation and cooling of the winding 40 and reduce the weight of the cover.

In the axial planes containing the inwardly projecting tabs 49 are outwardly projecting tabs 52 fixed to the ring 47, and positioned in the median plane thereof. The tabs 52 are connected to each other by reinforcing webs 53. The free ends of the tabs 52 carry prongs 54 parallel to the axis of the cover. The prongs 54 are connected to the tabs 52 by reinforcing webs 55. The tabs 52 are connected to the ring 47 by reinforcing webs 56. The assembly formed by the tabs 52 and their associated prongs 54 and by the various webs connected thereto has a zone of minimum thickness between the points at which the

webs

55 and 56 are connected, the teeth 37 of the cheek plates 36 of the rotor are positioned in this zone. These cheek plates embrace the cover shown on FIGS. to 12 in the general manner illustrated in FIG. 4. The flange 58 of the cover is provided with a slot 57 in an axial plane equidistant from the two connecting tabs 49, which cuts all the way through the connecting ring 50. The two outwardly projecting tabs 52 which are adjacent this slot are connected by a web 53 which comprises thickened portions 58 at the side of the web 53 connected to the flange 48. In the thickened portions 58 are two radial grooves 59. Between the slot 57 and each of the grooves 59 are two recesses 60 in the ring 47. The wire forming the winding 64) has two ends, one located near the center of the winding and the other in the peripheral part of this winding. The winding 40 is supplied through

wires

60a and 60b connecting the winding ends to a source of electric current in the direction of the stator of the machine, which is possible because in the electrical machine according to the invention the winding 40 is stationary. The wire 60a passes through the opening 57 one of the recesses 60 and the corresponding groove 59. The wire 60b passes through the other recess 60 and the corresponding groove 59.

When the winding 40 is mounted in the cover which has just been described, and the ends of this winding have been connected as hereinbefore indicated, the prongs 54 are inserted in the slots of the stator which are adapted to receive them as has been hereinbefore described in detail. It is obvious that the annular spacing between two successive prongs is a multiple of the angular spacing between two successive stator poles. At this stage the assembly comprising the stator, the secondary winding, the winding support and the inductive winding of the rotor is impregnated with a resin of the epoxy type. Assembly of the machine is then completed by mounting the two cheek plates 36 on opposite sides of the winding 40 on the shaft 34. In a fourth embodiment, illustrated on FIGS. 13 and 14, it will be seen that the rotary machine according to the invention is an alternator having a general construction analogous to those hereinbefore described. The cover for the rotor winding is in this case made in two identical halves 61a and 6M), each defining an annular seat 62. The cover halves 61a and 61b each comprise a bottom and are adapted to be assembled with the areas opposite their bottoms adjacent each other. The free edges of each cover half are provided with three radial mounting tabs 63. At the ends of these tabs 63 which are not attached to the cover halves is a prong 64 parallel to the axis of the cover halves. The middle of this prong is connected to the tab M. The cover halves Ma and 61b are adapted to be positioned relative to each other in such manner that each tab 63 on one half is positioned halfway between two tabs 63 on the other half, the angular distance which separates two successive tabs of the assembly formed by the two cover halves 611a, 61b being a multiple of the distance between the poles of the stator 2. The winding 10 of the rotor is mounted inside the an nular space formed by assembling the two cover halves together. The prongs 64 are mounted in certain of the slots of the stator, and the assembly formed by the two cover halves 61a and 6ib and the winding 10 is thereby firmly attached to the stator.

FIG. shows a fifth embodiment of the cover for the rotor winding. It will be seen that reference numeral 10 indicates the rotor winding and that this winding is positioned inside a ring of channel-shaped sectors 65 which define a seat 66 having a section substantially equal to the section of the winding 10. The sectors 65 are each provided with a mounting tab 67 and a prong 68. The latter is positioned at the end of the tab 67 which is not connected to the sector 65. The sectors 65 are angularly and regularly spaced about the winding 10. They are of an even number and the bottoms of alternate sectors may be mounted on opposite sides of the winding 10 of the rotor. When the various sectors 65 have been mounted on the winding 10, the prongs 68 may be slid into certain of the slots in the stator and the winding i0 is then firmly attached to the stator. It is held radially by the sidewalls of the sectors and axially by the bottoms of the sectors which are positioned alternately on opposite sides of the winding.

FIG. 16 represents a sixthembodiment of the machine according to the invention. It will be seen that reference numeral 10 indicates the rotor winding and this winding is positioned inside an annular cover having a U-shaped section comprising a bottom I01 and flanges 102a and l02b. The flange 102a forms the inner cylindrical wall of the cover 100. The flange 102b forms the outer cylindrical wall of the cover 100. Radial tabs 103 are mounted on the external cylindrical wall and carry at their ends the prongs 104 which are parallel to the axis of the cover. The angular spacing between two successive tabs 103 is a multiple of the polar pitch off the stator. When the winding has been mounted inside the cover 100 the prongs 104 are slid into certain of the slots in the stator to position the tabs 103 substantially in the median plane of the stator. The winding 10 is then firmly held with respect to the stator and may be secured inside the cover 100 by a suitable adhesive coating.

FIG. 17 represents a first variation of a seventh embodiment. In this variation the cover of the winding 10 is made from strips 69. The strips 69 are substantially rectangular and comprise at their two ends tabs 70 the width of which is less than the width of the strip 69. The strips 69 are mounted along the inner periphery of the winding 10 symmetrically with respect to the median plane of this winding and are bent to encircle the winding.

Tabs 70 are bent at right angles to the strip 69 so as to form prongs 71 the ends of which are also bent at right angles to form hooks 72. When a strip has been bent to completely encircle a section of the winding 10 it constitutes means permitting the attachment of the winding 10 at one point. The winding 10 is provided with strips 69 bent in this manner which are regularly distributed all around the winding with an angular spacing which is a multiple of the polar pitch of the stator. It should be noted that, in this embodiment, the hooks 72 do not pass through the median plane of the winding 10.

FIG. 18 shows a second variation of the seventh embodiment of the invention which has just been described. In this second variation the tabs 70 at the ends of the strips 69 are so folded that the prongs 71a pass through the median plane of the winding 10 and the hooks 72a are thus situated on the opposite side of the median plane of the winding 10 from the end zone of the strip 69 to which they are hooked.

FIGS. 19 and 20 represent a third variation of the seventh embodiment of the invention. In this variation the strips 690 which encircle a section of the winding 10 are connected to each other by circumferential rings 73. The cover for the winding 10 is then made from a cylindrical cage fonned by the strips 6% parallel to the axis of the cylinder and two circumferential rings 73 which connect these strips in a plane perpendicular to the axis of the cylinder. Such a cage is shown in perspective 0n FIG. 19. The winding 10 is then slid onto the cage, the inner diameter of the winding being substantially equal to the outer diameter of the cage. The ends of each of the strips 69a are then bent around the winding 10 which is positioned between the two circumferential rings 73. The ends of the strips 69a are then bent at right angles to form radial prongs 71a and then bent again at right angles to form the hooks 72b. It should be noted that because of the presence of the rings 73 it is not necessary for the strips 690 to be very wide, so that the ends of the strips 69a may be of the same width as the central portions thereof, whereas in the embodiments of FIGS. 17 and 18 these ends were made narrower to produce the tabs 70.

FIGS. 21 and 22 illustrate an eighth embodiment of the machine according to the invention. The cover for the rotor winding in this embodiment consists of a central plate 81 carrying back to back two

identical rings

82a, 82b each having a U-shaped section. The two

halves

10a and 10b of the rotor winding are lodged in the annular seats defined by the rings 82a and 62b. These windings are wound in the same direction and connected in series. The

rings

82a, 82b are riveted to the central plate 81, which is circular and carries radial peripheral

Claims

1. In a rotary electric machine comprising a stator winding, a stator slotted to receive said winding and a rotor comprising two coaxial magnetic cheek plates spaced by a coaxial magnetic core, each cheek plate carrying peripheral teeth parallel to the rotor axis separated by individual spaces, with the spaces between the teeth on one cheek plate being opposite the teeth on the other cheek plate and the ends of the teeth on the two cheek plates lyiNg in parallel axially spaced planes, said machine also comprising a rotor winding mounted between the two cheek plates around the magnetic core and supported by a cover attached to the stator by means having a thickness less than the gap between the two planes in which the ends of the rotor teeth lie, the improvement according to which the means attaching the cover of the rotor to the stator are radial tabs regularly spaced about the periphery of the cover and the outer ends of the tabs extend into certain of the slots in the stator.

2. A machine as claimed in claim 1 essentially characterized by the fact that the two cheek plates are identical and their teeth are trapezoidal in form as are the spaces between consecutive teeth.

3. A machine as claimed in claim 1 essentially characterized by the fact that the tabs connecting the winding cover to the stator comprise ridges increasing their section.

4. A machine as claimed in claim 1 essentially characterized by the fact that the tabs of the rotor winding cover terminate in prongs seated in certain of the slots in the stator.

5. Method of assembling an electrical machine as claimed in claim 4 in which the stator and the cover of the rotor winding are equipped with attaching tabs, and prongs at the tip of said tabs, said method comprising the steps of mounting the rotor winding and its cover in the stator by sliding said prongs into slots in the stator until they reach a predetermined position abutting at least one stop in said stator, impregnating the stator winding with a synthetic resin in order to fasten the wires of this winding and the attaching tabs together, fastening the two cheek plates of the rotor to the magnetic core, positioning the resulting rotor around the rotor winding which has been attached to the stator, and introducing the rotor shaft into the central bore of the cheek plates, into the core and into two bearings in the stator housing.

6. Machine as claimed in claim 4 essentially characterized by the fact that the prongs have a slightly trapezoidal section in the axial plane.

7. Machine as claimed in claim 4 essentially characterized by the fact that the rotor winding cover is made from a molding of nonmagnetic material.

8. Machine as claimed in claim 4 essentially characterized by the fact that the rotor winding cover is a box composed of two identical circular parts, each of which carries half of said tabs, which parts are attached together by engaging a contact surface on each tab of one part with a corresponding contact surface on a tab of the other part.

9. A machine as claimed in claim 8 essentially characterized by the fact that the substantially radial tabs of each half of the cover form a slight angle to the perpendicular to the axis of the box which passes through the foot of the tab in question each tab being attached at its end to a half hooking tab which is perpendicular to it.

10. Machine as claimed in claim 8 in which the tabs of the rotor winding cover are radial and perpendicular to the axis of the cover and comprise contact zones at a slight angle to the median plane of the cover, each tab being attached at one end to a prong perpendicular to said tab.

11. Machine as claimed in claim 4 in which the rotor winding cover is made in one piece and comprises an annular ring coaxial with the rotor, which ring is fastened to a lateral flange perpendicular to the axis of the rotor, said flange being radially notched to permit the passage of wires for connection to the winding of the rotor, the radial tabs with which the cover is provided being fast to the annular ring and carrying at their end prongs which are parallel to the axis of the cover.

12. Machine as claimed in claim 11 in which the radial tabs of the cover are connected to each other by reinforcing webs and are provided with reinforcing webs parallel to the axis of the cover.

13. Machine as claimed in claim 11 in which the annular ring of the cover is slotted in alignment with the notch in the flange of the cover and the web between the adjacent tabs is recessed to admit wires for connection to the winding of the rotor.

14. Machine as claimed in claim 4 in which the rotor winding cover is made in two parts, each part being equipped with radial tabs and each tab terminating in a prong parallel to the axis of the cover and fastened at its midpoint to the corresponding tab, said prongs being seated in certain slots in the stator, and the tabs of one of the cover halves being angularly spaced with respect to the tabs of the other half.

15. Machine as claimed in claim 4 in which the cover of the rotor comprises several independent concave sectors having a U-shaped section of a depth substantially equal to the thickness of the winding, said sectors being mounted alternately on opposite sides of the winding and each being provided with at least one radial tab on its circumferential exterior lying substantially in its median plane, each tab terminating in a prong parallel to the axis of the corresponding sector and preferably attached to its center to the tab which supports it, the prongs being seated in certain of the slots in the stator so that the tabs are located in the median plane of the stator.

16. Machine as claimed in claim 4 in which the rotor winding cover consists of a circular box having a U-shaped section substantially equal in depth to the axial thickness of the winding, the rotor winding being positioned inside the annular space defined by said box, said box carrying on its external periphery a plurality of radial tabs, each of which carries a prong parallel to the axis of the cover, said prongs being seated in certain of the slots of the stator so that the tabs are positioned substantially in the median plane of the stator.

17. Machine as claimed in claim 4 in which the rotor winding cover is made of several strips which encircle the ring forming said winding, the ends of said strips being bent perpendicularly to the outer surface of the ring formed by the winding at a position near the median plane thereof so as to each form a radial tab, which tab is then folded at right angles to provide at each end of the strip a hook parallel to the axis of the winding, each hook being a slot in the stator.

18. Machine as claimed in claim 17 in which the bent back ends of the strip which form the cover for the rotor winding are situated on opposite sides of the median plane of the winding, each strip being independent of the adjacent strip.

19. Machine as claimed in claim 17 in which the tabs formed at the ends of the strips from which the rotor winding cover is made extend across the median plane of the winding and serves as hooks by crossing the tabs at ends of at least one adjacent strip, said strips being independent of each other.

20. Machine as claimed in claim 17 essentially characterized by the fact that the strips comprising the rotor cover are connected together by circumferential rings.

21. Machine as claimed in claim 17 in which the strips of which the rotor cover is made are molded around the rotor winding.

22. Machine as claimed in claim 4 in which the winding of the rotor comprises two parts wound in the same direction, and the cover for these two parts comprises a central plate carrying peripheral mounting means which cooperate with the stator and two hollow annular seats, each seat containing one of the winding halves.

23. Machine as claimed in claim 17 in which the mounting means at the periphery of the central plate consist of radial tabs carrying at their ends prongs which are parallel to the axis of the rotor winding cover.

24. Machine as claimed in claim 17 in which the mounting means at the periphery of the central plate consists of radial mounting tabs which carry at their ends a hook formed by bending the tab at right angles, two consecutive tabs carrying hooks which extend in opposite directions from the central plate.

25. Machine as claimed in claim 1 in which the means by which the rotor winding cover is attached to the stator comprises tabs which are held in slots in the stator by means of wedges.

26. Machine as claimed in claim 25 in which the rotor winding cover consists of a box carrying projections on its external circumference substantially in its median plane projections, the end width of said projections being slightly greater than the distance between two pole shoes of the stator, said projections having a central arcuate portion and being angularly spaced by a distance equal to the pitch between the slots of the stator.

27. Machine as claimed in claim 26 in which the attaching means carried by the central plate are projections provided with a central arcuate portion, the ends of said projections being slightly wider than the space between two consecutive stator pole shoes, and said projections being spaced one from the other by a distance equal to the pitch between the notches of the stator.

28. Machine as claimed in claim 25 in which the cover for the rotor winding is made of two halves which receive the rotor winding, each box half comprising in the zone in which it comes in contact with the other box half a flat annular plate perpendicular to the axis of the box and carrying on its periphery regularly spaced attaching tabs having a curved section, said curved sections being so positioned that their concavities face each other when the two box halves are assembled.

29. Machine as claimed in claim 25 in which the cover for the rotor winding is provided at its periphery with radial fastening tabs spaced one from the other by an angular distance which is a multiple of the polar pitch of the stator and which have a thickness less than the width of the notches of the stator, said radial tabs abutting an element fixed to the stator, which element has a face near the median plane of the stator, and said machine comprising radial tabs wedge means which retain said tabs in abutment with said element.

30. Machine as claimed in claim 29 in which the radial tabs of the rotor winding cover abut a first series of wedges which are preferably nonmagnetic and fixed within the notches of the stator and that the tabs are radially retained in position against said wedges by means of a second series of wedges which close the zone of the slots through which the radial tabs are introduced to bring them into abutment with the first series of wedges.

31. Machine as claimed in claim 29 in which the stator consists of a stack of laminations, and one lamination in said stack situated substantially in the median plane of the stator has smaller slots so that the radial tabs of the stator winding cover abut projections formed in the stator slots by the said one lamination and the radial tabs are retained in position against said lamination by means of wedges.

32. Machine as claimed in claim 29 essentially characterized by the fact that the stator consists of a stack of laminations, and one of these laminations lying substantially in the median plane of the stator is shaped to define a recess in one side of at least one notch, said recess having a depth less than the depth of the pole shoes, and the thickness of said one lamination being substantially equal to the thickness of the radial tabs of the rotor winding cover, and said tabs are seated in said recesses and retained in position by wedges.

33. Machine as claimed in claim 1 in which the poles of the stator have in a section perpendicular to the axis of said stator an accentuated trapezoidal shape and conventional pole shoes, but having a width at their bases between 40 percent and 70 percent of the width of the bases of the poles of a conventional type of stator pole.