Flux-switching electrical machine

Abstract

A singly-excited flux-switching electrical machine, that includes field coils and phase windings, is provided. The field coils and the phase windings are accommodated respectively in the unevenly shaped notches of a stator, such that the field coils and phase windings are radially offset.

Claims

1. A single excitation flux-switching electrical machine, comprising excitation windings and phase windings, the excitation windings and the phase windings being housed in respective grooves in a stator, of unequal shape, such that the excitation windings and the phase windings are offset radially.

2. The machine as claimed in claim 1, wherein the excitation windings are closer to an air gap than the phase windings.

3. The machine as claimed in claim 1, wherein 0.65a/b0.85, where a is the angular width of a tooth at the air gap and b is the angular width of a groove at the air gap.

4. The machine as claimed in claim 3, wherein 0.7a/b0.8.

5. The machine as claimed in claim 1, the phase windings and the excitation windings overlapping one another radially.

6. The machine as claimed in claim 1, the grooves housing the windings radially further from a rotor having a greater circumferential dimension larger than the greatest circumferential dimension of the grooves housing the windings distanced less far radially from the rotor.

7. The machine as claimed in claim 1, the windings housed in the grooves radially further from the rotor occupying a section S1 and the windings housed in the grooves distanced less far radially from the rotor occupying a section S2, where S2S1.

8. The machine as claimed in claim 1, the base of the grooves radially further from the axis of rotation of the rotor being arranged at a distance R2 and the base of the grooves arranged less far from the axis of rotation being arranged at a distance R1 therefrom, where 0.8R1/R21.0.

9. The machine as claimed in claim 1, the grooves radially further from the axis of rotation of the rotor having, between the winding received by the groove and the air gap, opposed edges diverging in the direction of the rotor, then opposed edges converging in the direction of the rotor.

10. The machine as claimed in claim 9, the angle of divergence being between 50 and 60.

11. The machine as claimed in claim 9, the divergent edges being connected at their radially outermost end to convergent edge.

12. The machine as claimed in claim 11, the convergent edges being connected to a shoulder.

13. The machine as claimed in claim 1, the grooves housing the windings distanced less far radially from the rotor comprising reliefs for fixing chocks for retaining the windings.

14. The machine as claimed in claim 1, comprising a single phase winding per groove.

15. The machine as claimed in claim 1, comprising two phase windings per groove.

16. The machine as claimed in claim 1, with a number of stator teeth n.sub.ds equal to 24 and a number of rotor teeth n.sub.dr equal to 14.

17. The machine as claimed in claim 1, the phase windings housed in the grooves being arranged in two superimposed layers, the conductors associated with each layer occupying the same regions of the two layers, the conductors of the excitation windings arranged in the grooves being arranged in two nested layers, the conductors of the same winding being arranged in different regions of the grooves.

18. The machine as claimed in claim 1, the phase windings housed in the grooves being arranged without superimposing one another radially in these grooves, and the excitation windings housed in the grooves being disposed without superimposing one another radially in these grooves.

Description

(1) The invention will be better understood upon reading the detailed description hereinafter of non-limiting embodiments of the invention and upon examining the accompanying drawing, in which:

(2) FIG. 1 shows part of an example of a stator formed in accordance with the invention,

(3) FIGS. 2 and 3 illustrate two possibilities for arranging windings of the stator in the grooves, and

(4) FIGS. 4 and 5 show two exemplary embodiments of a stator winding.

(5) FIG. 1 schematically shows a stator 1 of a single flux-switching machine, said stator being designed to cooperate magnetically with a rotor which is devoid of permanent magnets and comprises, for example, n.sub.dr teeth arranged equidistantly on the periphery of the rotor.

(6) The stator 1 comprises two sets of grooves, that is to say a first set of grooves 3 receiving the excitation windings E and a second set of grooves 5 receiving the phase windings A, B and C in the case of a three-phase machine.

(7) In accordance with the invention, the grooves 3 and 5 are offset radially, the base 6 of the grooves 5 being arranged at a greater distance from the axis of rotation than the base 7 of the grooves 3.

(8) In FIG. 1 some grooves 3 or 5 have been shown without the windings so as to show the contour more clearly.

(9) As illustrated, the grooves 3 may comprise, close to the air gap, reliefs 10 in the form of small necks for receiving chocks 11 for retaining the windings, said chocks being mounted slidingly in the necks 10 (not illustrated).

(10) The grooves 5 have a shoulder 13, which can serve to rest against the conductors housed inside. The shoulder 13 borders a passage 15 formed between the convergent edges 16, which are connected in the direction of the air gap to edges 17 which diverge as they near the rotor and in turn are connected to edges 18 which converge as they near the rotor.

(11) The edges 18 are preferably as radial as possible so as to produce a passage of excitation flux of substantially constant density in the direction of the air gap.

(12) If a and b denote the respective angular widths of a tooth and a groove at the air gap, then the following is preferably true: a/b0.75.

(13) The angular width b of the grooves 3 at the air gap is preferably equal to that of the grooves 5.

(14) In the drawing, R.sub.2 denotes the distance from the base 6 of the groove 5 to the axis of rotation of the rotor, R.sub.1 denotes the distance from the base 7 of the groove 3 to the same ads, and R.sub.3 denotes the distance from the winding received in the groove 5 to the axis of rotation, that is to say the distance from the shoulder 13 to this axis. The coils received in the grooves 3 are arranged at a distance R.sub.4 from the axis of rotation. Preferably, 0.8R.sub.1/R.sub.21.0, which facilitates the mounting of the windings in accordance with a nested configuration, as described further below with reference to FIG. 5.

(15) In addition, the angle of divergence of the edges 17 is between 50 and 60, for example.

(16) As can be seen in FIG. 1, the grooves 5 which are further from the axis of rotation than the grooves 3 may have at greater circumferential dimension l.sub.1 larger than the greatest circumferential dimension l.sub.2 of the grooves 3.

(17) The machine comprises a sequence of basic cells each formed by at groove containing the conductors or E+ or E of an excitation winding E and by two adjacent grooves receiving the conductors of the phase coils A+, A, B+, B, C+ or C, the machine being multi-phased, in particular three-phased, A, B and C denoting the phases.

(18) By convention, the signs + and are attributed to the conductors depending on whether they have one direction or another within the groove. The same excitation coil thus comprises conductors E+ and E.

(19) The excitation windings E are connected conventionally to a direct current source.

(20) The axis of each coil is oriented substantially radially, the machine being what is known as a radial machine.

(21) FIGS. 2 and 3 illustrate exemplary configurations for filling the grooves. In this figure, the suitor is represented linearly with equal grooves 3 and 5 for clarity and simplification of the drawing.

(22) The grooves which receive the phase windings may each receive a single phase winding, as illustrated in FIG. 2, for example with, as illustrated, an alternation in the circumferential direction between the conductors E+ et E of the excitation windings and those of the phase windings, for example with, as illustrated, the sequence of phase conductor A+, excitation conductor E+, phase conductor A, excitation conductor E, phase conductor excitation conductor phase conductor B.

(23) In a variant, as illustrated in FIG. 3, the winding is said to be double-layered, that is to say a groove receiving, the phase windings receives the windings of two phases, for example A+ and C, B+ and A, C+ and B, A+ and C, as illustrated.

(24) The phase windings A, B or C can each be arranged, as illustrated in FIG. 4, in a layer 67, the electric conductors of the same phase winding, occupying groove portions arranged at the same distance from the axis of rotation. Two phase windings having conductors received in the same groove 5 are not superimposed radially. The same may be true of the excitation windings E. It can be seen in FIG. 4 that the coil heads are not nested.

(25) In FIG. 5 a configuration in which the phase windings A, B or C are arranged in two layers 60, 61 in a manner radially superimposed in the grooves 3 is shown. The electric conductors in the same layer 60 or 61 occupy groove portions arranged at the same distance from the axis of rotation.

(26) The excitation windings E are arranged in two nested layers 63, 64, that is to say the conductors in the same layer 63 or 64 are arranged in portions 3a, 3b of two consecutive grooves 3, arranged at different distances from the axis of rotation. Thus, the same excitation winding comprises, on the one hand, conductors arranged in the portion 3b of the groove 3 closest to the air gap, and, on the other hand, in the adjacent groove 3, conductors arranged in the portion 3a of the groove furthest from the air gap.

(27) The invention is not limited to these specific configurations of grooves and windings, and, for example, basic cells may be provided of which the grooves receiving the excitation conductors E+ and E respectively of the same excitation coil are separated by a different number of teeth.

(28) The expression comprising a is to be understood as a synonym of comprising at least one.