FR2842361A1 - High efficiency alternators having magnetic body with winding and shock absorbers carrying electrical conductor through holes perpendicular rotation axis. - Google Patents

Abstract

The alternator has a rotor with a rotation axis (X). there is a magnetic body with windings. Shock absorbers carry electrical conductors through holes. The holes are in a perpendicular plane to the rotation axis.

Description

The present invention relates to electric rotating machines, and

  more particularly, but not exclusively, alternators intended for generator sets and of a power ranging for example from a few kilowatts to a few tens of

  kilowatts, for example less than 30 kW.

  Magnetic rotor sheets each having two notches for

  receiving the inductor windings are known, in particular from application JP 61 214640.

  These sheets also include passages for shock absorbers which are intended for

attenuate the harmonics.

  There is a need to further improve the attenuation of harmonics and / or to promote the circulation of magnetic flux in the rotor, without however increasing

  measures the manufacturing cost of the rotor.

  The invention thus relates to an electric rotary machine comprising: - a rotor capable of rotating around a geometric axis of rotation, this rotor comprising: - a magnetic carcass comprising notches receiving windings, and - dampers comprising electric conductors passing through corresponding passages of the magnetic carcass, this machine being able to be characterized by the fact that said passages are arranged, when the rotor is observed in a plane perpendicular to the axis of rotation, in a manner not

  symmetrical with respect to any plane containing the geometric axis of rotation.

  Thanks to this arrangement of the passages, the attenuation of the harmonics and / or the

  circulation of magnetic flux can be improved.

  The spacing between two consecutive passages, when one moves circumferentially around the geometric axis of rotation of the rotor on one side of a median plane, may be non-constant. In particular, this spacing can vary, for example, monotonically, and increase when one moves circumferentially in the direction of rotation of the rotor. This can improve the operation of the machine, by

charge in particular.

  According to another aspect of the invention, at least one passage may have a non-circular cross section. In particular, at least one passage may have an oblong cross section, having an axis of larger dimension oriented substantially radially. The carcass may include a packet of magnetic sheets each having

axial symmetry.

  The shock absorbers may include bars, for example ten in number, produced by injecting a conductive metal into the passages of the carcass. The number of notches can be equal to two, which facilitates the setting operation

in place of the rotor windings.

  The magnetic carcass can be laminated or not.

  The machine can constitute an alternator, in particular for a generator.

  The invention will be better understood on reading the description which will

  follow, from an example of non-limiting implementation, and on examining the appended drawing, in which: - Figure 1 shows, schematically and in perspective, an example of an alternator casing produced in accordance with invention, - Figure 2 is an axial section, partial and schematic, of an alternator comprising the housing of Figure 1, - Figure 3 shows in isolation, in side view, the housing of Figure 1, Figure 4 is a top view, schematic and partial, according to arrow IV in FIG. 3, - FIG. 5 is a front view, schematic and partial, with cutaway, according to arrow V in FIG. 4, - FIG. 6 is a front view, diagrammatic and partial, according to arrow VI in FIG. 4, - FIG. 7 represents in isolation, in section in a median plane, a brush holder, - FIG. 8 is a plan view, schematic and partial, according to arrow VIII of Figure 7, - Figures 9 to 11 show, in front view, d various examples of rotor sheets of the prior art, - FIG. 12 represents, in front view, a rotor sheet provided with shims, - FIG. 13 represents in isolation, in perspective, a shim, - Figures 14 and 15 represent of partially and schematically, in front view respectively at each end, the rotor with the "rings" of short-circuit, - Figure 16 represents in isolation, in front view, the connecting piece, and

  - Figure 17 is a section along XVII-XVII of Figure 16.

  FIG. 1 shows an alternator 1 comprising a metal casing 2 and a cover 3 attached to the casing 2. The alternator 1 is intended, in the example considered, to be fixed to a heat engine, not shown, for form a generator. The cover 3 which can be made of metal or plastic shelters, for example, a conventional electrical circuit not visible in the figures, for regulating and connecting the alternator. The alternator 1 comprises, as can be seen in FIG. 2, inside the casing 3, a stator 4 and a rotor 5 which can rotate inside the stator 4 around a geometric axis of rotation X. The rotor 5 comprises a shaft 6 on which is fixed a magnetic carcass 7

  receiving inductor windings 8.

  The rotor 5 rotates a fan 9 intended to generate a current

cooling air.

  Casing The casing 2 comprises a cylindrical body of revolution 12, which is connected at a first longitudinal end, by an enlarged part 20, to a flange 13 used for fixing the alternator to the heat engine, via a connecting member, as it will

clarified below.

  The flange 13 has holes 40 each of axis Y, which are located

  radially outside the envelope of the cylindrical body 12.

  The casing 2 also comprises, at a second longitudinal end opposite the first, a perforated transverse wall 14 and a bearing 15 for supporting the

the rotor shaft.

  Reinforcement ribs 16 extend radially between the bearing 15 and the

cylindrical body 12.

  The flange 13 and the bearing 15 are made in one piece with the rest of the housing,

  by aluminum foundry in the example considered.

  It can be seen in FIGS. 1 and 3 in particular that the casing 2 comprises in the upper part two lateral extensions 18, extending over the major part of the cylindrical body 12, on which the cover 3 rests, these extensions 18 being each provided with a plurality of openings 19 allowing air to enter under the hood, as will be

specified later.

  The enlarged part 20 which is made in one piece with the rest of the casing defines a housing for the fan 9. Two lateral openings 21 are made in the enlarged part 20 to allow the exit of the cooling air. Only one of these openings is visible in Figures 1 and 3. Protective bars 22 are present in each opening 21 to protect personnel from contact with the fan in operation. The bars 22 are made in one piece with the casing 2, by foundry. Before machining, the bars 22 are linked on the inside by a web of material

come from foundry.

  The casing 2 undergoes, after its molding and fixing of the stator, a machining intended in particular to produce a cylindrical surface of revolution around the axis X inside the bearing 15 to receive a cage 11 containing the support bearings of the rotor shaft. The radially inner side of the bars 22 is machined to remove the above veil. This machining takes place in a single pass, in order to avoid a second pass which would be

  likely to damage the bars 22.

  It can be seen in FIG. S that ribs 41 form a projection on the radially inner surface of the cylindrical body 12, for fixing the stator. The ribs 41 are produced by molding with sufficient precision so as not to have to undergo machining. The transverse wall 14 has openings 43 to allow air to enter

in the crankcase.

  Air outlet grids The bars 22 each have a longitudinal axis Z which extends, as can be seen in particular in FIG. 3, parallel to a plane perpendicular to the geometric axis X of rotation of the rotor, ie substantially vertically in the example considered. The axis Z is not straight, the bars 22 each comprising a central curved portion 22a having a concave inner side towards the axis X. It may also be noted, on examining FIG. 3, that the bars 22 are connected to their longitudinal ends to the rest of the casing 2 and are devoid, over their length, between their longitudinal ends, of connections between them. The grids formed by the bars 22 are therefore devoid, in the example considered, of horizontal bars. This arrangement reduces the pressure drop across the openings 21 and improves the efficiency of ventilation. We see in Figure 5 that the enlarged portion 20 defines two passages 91 in the form of a scroll. These two passages 91 are, in the example considered, substantially the image of one another by an axial symmetry of axis X. Each passage 91 has a section offered to the passage of air which

  increases as you approach the exit.

  In Figure 5, the fan rotates clockwise.

  Each passage 91 has an enlarged portion 91a adjacent to a portion 22b of the bars 22. This portion 22b is connected at one end to the casing 2 and at the other end to the corresponding central portion 22a and forms with this latter a concavity turned towards the 'outside. This allows to have the connection portion 22b

  directed substantially perpendicular to the direction of air flow.

  The bars 22 are two in number by lateral opening 21, in

  the example considered, but this number could, of course, be different.

  The casing 2 comprises, in the upper part, as can be seen in FIG. 4, a first opening 24 intended to allow the fixing, inside the casing, of a

  brush holder 30, shown diagrammatically in FIGS. 7 and 8.

  The casing 2 also comprises, in the upper part, a second opening intended to allow, with the opening 24, a circulation of cooling air and the

  passage of the stator electrical conductors.

  Brush holder We see in Figures 7 and 8 that the brush holder 30 comprises on the one hand a support portion 31, on which are fixed conventional brushes 32, also called "brushes", intended to come into contact, by one end 3 2a, with rings 110 of the rotor collector, also called "slip rings", and on the other hand a fixing part 33, intended to engage in a slide 35 produced on the inner face of the transverse wall 14 of the casing 2 and with the latter, this slide 35 being vertical in the example considered. The brushes 32 are connected to lugs 32b for connecting the conductors

  rotor power supply, not shown.

  A groove 39 is formed between the support 31 and fixing 33 parts for

  cooperate with returns 36 of the slide 35.

  The fixing part 33 has an extension 37 provided with a hole 38 for the passage of an immobilizing screw intended to engage in the transverse wall 14. The brush holder comprises stiffening webs 31a and 33a associated respectively to the support 31 and fixing 33 parts and which extend substantially parallel to a plane containing the geometric axis of rotation X and coincides with the plane

section of Figure 2.

  The support 31 and fixing 33 parts are produced in the example described

  in one piece by molding insulating plastic.

  The brush holder 30 is fixed on the casing 2 by being first introduced by the first opening 24 inside the casing 11, then sliding the fixing part 33 in the slide 35, then the brush holder 30 is immobilized axially in the slide 35 by means of a screw inserted in the hole 38 and cooperating with the wall

transverse 14.

  Rotor The carcass 7 of the rotor 5 is laminated in the example considered and comprises a stack of magnetic sheets 60 each comprising notches 61 in which

  are engaged the son of the windings 8. The carcass 7 may still not be laminated.

  In the example considered, the rotor 5 is of the salient pole type.

  FIGS. 9 to 11 show different examples of forms of rotor sheets encountered in known alternators, the rotor of which has two polar parts. In these examples, each sheet has notches 50 for receiving the inductor windings and passages 51 for the shock absorbers intended to attenuate the

  generation of harmonics, these dampers being also called "damper windings".

  We see that the notches 50 are arranged symmetrically on either side of a median plane M containing the geometric axis of rotation, and that each sheet can comprise for example eight notches, as shown in FIG. 9, or four notches

  as shown in Figures 10 and 11.

  We also note that the passages 51 for the shock absorbers are in known circular alternators and arranged near the radially outer edge of the pole parts, symmetrically with respect to the median plane M. In the embodiment considered, each magnetic sheet 60 has the shape shown in Figure 12 and has an axial symmetry with respect to the axis X. The notches 61 are arranged symmetrically on either side of a median plane M containing the axis X, to receive the windings d inductor 8, not shown in FIG. 12, which can be, as in the example illustrated, electrically connected to the rings 110 of the collector, on which the brushes come to apply

32 described above.

  Each sheet 60 defines two opposite polar parts 75 which are provided

each of two polar horns 68.

  Inductor winding shims The windings are held in the notches 61 by shims 63, one of which

  of them is shown in isolation, in perspective, in FIG. 13.

  Each wedge 63 is made, in the example considered, from an insulating plastic material and has, in section in a plane perpendicular to the axis X, a general V shape with two wings 64. Each wing 64 comes to bear, by its free end 65, against the inner edge 67a of a pole horn 68 near its free end. It can be seen in the figures that the wedges 63 each have two beads of material 100 which protrude from the outer faces 69c of the wings 64, near

their free ends.

  Each wing 64 has an inner face 69a, facing the pole portion

  corresponding, which is generally concave.

  Each wedge 63 comes by its base in abutment or almost against the metal sheet package 60 of the rotor, possibly by means of an insulating sheet placed in the notch 61 before the windings. A wedge 63 therefore delimits two regions in the notch 61, the latter receiving the coils associated respectively with the two pole parts 75. The base of the wedge 63 has a generally flattened face 69b which is positioned opposite an edge 67b of the notch 61, this edge 67b being generally convex towards the outside. It can be seen in FIG. 12 that, taking into account the shape of the edge 67b, the section offered for the passage of the magnetic flux does not pass through a minimum at the level of the plane P containing the axis X and perpendicular to the median plane M. of their shape, the two wings 64 of each shim 63 provide between them and with the stator a space 70 of non-negligible section which allows circulation

  increased air between the rotor and the stator. The cooling of the rotor is thereby facilitated.

  In the example considered, the section Se delimited by the cylindrical envelope of revolution E of the rotor resting on the polar horns 68 and the shim 63 is greater than about a quarter of the section Si of the notch on the inner side of wedge 63. Several wedges

  63 succeeding each other along the X axis can be associated with each notch 61.

Arrangement of shock absorbers

  Each sheet 60 has passages 71 for shock absorbers.

  These passages 71 have, in the example illustrated, a non-circular shape.

  More specifically, in the example considered, each passage 71 has in cross section, as can be seen in FIG. 12, an oblong shape, of large dimension oriented radially, with two large sides 72 diverging radially outwards, these sides 72 being joined at their axial ends by semicircular edges 73 and 74. The semicircular edge 74 has a vertex close to the radially outer edge of the associated pole part 75. If we compare to a passage of circular section, the shape of the passages 71 and the radial orientation of the latter facilitates

  the circulation of the magnetic flux from one pole part 75 to the other.

  It can be seen in FIG. 12 that, on each side of the plane P, the spacing between the passages 71 is irregular. More particularly, in the example considered, the spacing between the passages 71 increases as one moves circumferentially in the direction of movement of the needles of a watch around the axis X. In FIG. 12, the direction of rotation R of the rotor is clockwise, the rotor being seen from the side opposite the end of attachment to the heat engine. This arrangement of the passages 71 makes it possible to attenuate the harmonics more effectively. The spacing between the passages 71 is in particular different from the dental pitch of the stator and facilitates the passage of the flux where the spacing is greatest. The operation of the alternator under load is

finds improved.

  The spacing between the passages 71 can be determined by a finite element calculation, for example so that the flow circulating between the passages 71 does not

  not exceed a predetermined value.

  The passages 71 are, in the example considered, five in number on each side of the plane P. The passages 71 arranged on one side of the plane P are for each sheet 60 the image of the passages located on the other side of the plane P, by an axial symmetry of axis X. The dampers can be produced by injecting under pressure a conductive metal in the fluid state, for example aluminum, in the passages 71 of the sheet pack 60, so as to form 140 conductive bars of electricity. The sheets 60 are superimposed with a slight angular offset between them, so that the bars 140

  each follow a path in the form of a propeller portion, in a conventional manner.

  The bars 140 associated with each pole portion 75 are electrically connected to each other, at each axial end of the rotor, by connection strips 190 and 195

  also called short-circuit "rings".

  FIG. 14 shows the connecting strips 190 on the side of the bearing 15 and

  in FIG. 15, the connecting strips 195 on the side of the fan 9.

  We see in these figures that each strip 190 or 195 electrically connects two bars 140 located on one side of the median plane P to three bars 140 located on the opposite side of

ceplanP.

  For each end face, the two strips 190 or 195 are thus not

  contiguous and have a shape that allows them to bypass the rotor shaft.

  Attaching the alternator to the heat engine In the example considered, the alternator is attached to the engine by means of a connecting member 120 which has been shown in isolation in FIGS. 16 and 17. This connecting member 120 comprises a plate 130 traversed by a central opening 121 to allow passage of the end of the rotor shaft to be coupled with

the engine shaft.

  The plate 130 comprises a first set of holes 122 intended to allow its fixing to the heat engine and a second set of holes 123 intended to allow the fixing of the flange 13 of the alternator. In the example illustrated, nuts 125 are welded to the plate 120 opposite each hole 123, on the side intended to face the

thermal motor.

  It can be seen in FIG. 17 that the plate 120 is non-planar, and that it can include stiffening ribs 131. The plate 120 has a first planar surface 126 in the vicinity of its outer periphery, intended to come into abutment against the flange 13 of the casing 2, and a second flat surface 127 bordering the opening 121 and intended to come into abutment against the heat engine. The two surfaces 126 and 127 are offset

  axially from a distance greater than the thickness of the nuts 125.

  Projecting parts 128 are intended to cooperate with the casing, being for example welded to the plate 130, in order to contribute to the centering of the connecting member

on the alternator.

  To fix the alternator on the engine, we first fix the plate 130 on the latter, by introducing fastening elements such as screws in the holes 122, then the alternator can be fixed on the plate 130 by introducing elements of

  fixing such as screws in the passages 40 and the holes 123.

  It will be noted that by the arrangement of the passages 40 outside the envelope of the cylindrical body 12, it is very easy to install the fastening elements of the alternator casing on the connecting member 120. The fasteners can be screwed for example by means of a key without having to engage the latter through a cooling air outlet opening, unlike known alternators. Of course, the invention is not limited to the embodiment which comes

to be described.

  In particular, without departing from the scope of the present invention, the

casing otherwise.

  Throughout the description, including the claims, the expression

  "comprising a" should be understood as being synonymous with "comprising at least

  a ", unless otherwise specified.

he

Claims (10)

  1. Electric rotary machine (1), comprising: - a rotor (4) which can rotate about a geometric axis of rotation (X), this rotor comprising: - a magnetic carcass (7) comprising notches (61) receiving windings (8), and - dampers comprising electrical conductors (140) passing through corresponding passages (71) of the magnetic carcass, machine characterized in that said passages (71) are arranged, when the rotor is observed in a plane perpendicular to the axis of rotation, asymmetrically by   relation to any plane containing the geometric axis of rotation (X).   2. Machine according to the preceding claim, characterized in that at   at least one passage (71) has a non-circular cross section.   3. Machine according to the preceding claim, characterized in that at least one passage (71) has an oblong cross section, having one more axis   large dimension oriented substantially radially.   4. Machine according to any one of the preceding claims,   characterized in that the spacing between two consecutive passages (71), when one moves circumferentially around the geometric axis of rotation of the rotor on one side   of a median plane (P), is not constant.   5. Machine according to the preceding claim, characterized in that said spacing increases when one moves circumferentially in the direction of rotation (R) of the rotor.   6. Machine according to any one of the preceding claims,   characterized in that the carcass (7) comprises a pack of magnetic sheets (60)   each with axial symmetry.   7. Machine according to any one of the preceding claims,   characterized in that the shock absorbers comprise bars (140) produced by   injection of a conductive metal into the passages (71) of the carcass.   8. Machine according to claim 7, characterized in that the number of bars equals ten.   9. Machine according to any one of the preceding claims,   characterized in that the number of notches (61) is equal to two.   10. Machine according to any one of the preceding claims,   characterized by the fact that it constitutes an alternator.