WO1993010592A1

WO1993010592A1 - Ring armature core for dynamo-electric machines having an intrinsic heat exchanger

Info

Publication number: WO1993010592A1
Application number: PCT/FR1992/001011
Authority: WO
Inventors: Thierry Rahban
Original assignee: Thierry Rahban
Priority date: 1991-11-18
Filing date: 1992-10-29
Publication date: 1993-05-27
Also published as: FR2683959B1; FR2683959A1; AU3088492A

Abstract

An armature core (5) for a dynamo-electric machine, comprising a multiplicity of plates made of a magnetic material and juxtaposed to form a hollow cylinder. Said plates are parallel to the rotational axis of the machine and electrically insulated, and form at one end a heat exchanger. This principle allows both smooth cores and toothed/slotted cores to be produced with a very low hysteresis loss and improved heat transfer. Said core may particularly be used in ring armatures for dynamo-electric machines.

Description

ANNULAR ARMATURE CORE OF DYNAMOELECTRIC MACHINES WITH INTRINSIC HEAT EXCHANGER

The present invention relates to an annular armature of a dynamo-electric machine.

Dynamo-electric machines having one or more coaxial annular rotors and stators with radial air gaps are known to those skilled in the art to provide a significant gain in specific power compared to conventional machines. French patent 1211092 thus proposes to insert between two magnetic rings, one being a multipolar inductor, the other serving as magnetic looping, an annular armature formed of circular sheets stacked in the axial direction. In French patent 1339895, the structure is similar but the second magnetic ring is also a multipolar inductor, opposite the exact magnetic first, which reduces the dispersion fields. In these two patent examples, the armature is mobile (rotor) while the inductor is static (stator), this solution being preferable due to the presence of a mechanical switch. Nowadays, the use of an electronic switching device makes it possible to reverse the roles, the armature becoming static and the mobile inductor. The realization then becomes easier, eliminating even any sliding contact if the inductor is with permanent magnets. It is advantageous to increase the useful field and the linear load as much as possible, which reduces the size of the machine. However, the mechanical, electrical and thermal stresses applied to the armature are becoming more and more severe. Also, the armature conductors are most often divided to reduce the eddy currents, transpo¬ ed, compressed according for example to French patent 1429469, then fixed to a magnetic core of laminated sheets resistant to the intense forces applied. Until now, the manufacture of this magnetic core consisted of stacking in the axial direction a bundle of thin annular sheets with high magnetic permeability. To reduce the fall of material, the rings can be divided into multiple sectors juxtaposed, or produced with a single laminated strip curved on a spiral edge, as respectively in French patents 2536222 and 2424656.

REPLACEMENT SHEET Efforts to further reduce the size of the machine are limited by its ability to dissipate calories through an increasingly limited space. The temperature can then rise to unacceptable values, with an increasing contribution of the inherent losses of the armature core, commonly called iron losses. This problem is even more sensitive when the inductor uses magnets made of magnetic powder mixed with a binder or compacted, since their operating limit temperature is lower than for sintered magnets or a wound inductor.

This is why the invention aims to improve the heat exchange capacity of the armature with the outside of the machine while reducing the losses generated locally by the armature core. This problem is solved by using the armature core itself as the preferred heat sink to dissipate calories. In order to reduce the thermal resistance in the axial direction, the armature core consists of a multiplicity of thin blades juxtaposed parallel to the axis of rotation of the machine, made of magnetically permeable material and good thermal conductor . Some blades are longer, and possibly wider, at at least one end, so as to delimit cooling fins between which can circulate a heat transfer fluid. Other characteristics and advantages of the invention will appear with the following description of some of its embodiments given by way of nonlimiting example, with reference to the attached drawings in which:

- Figure 1 is a longitudinal half-section of a dynamo-electric machine with two stators and three coaxial rotors, the rotors being shown in dotted lines, and the stators using two variants of armature cores according to 1 * inventio.

- Figure 2 shows a diametrical half-section corresponding to a section AA of Figure 1.

- Figure 3 shows four types of blades generally necessary to form an armature core with notches according to the invention. - Figure 4 shows a detail of the section of a notched armature equipped with its winding, according to section BB of Figure 1.

- Figure 5 shows various forms of imprints improving the rigidity of the blades.

- Figure 6 shows a variant of toothless armature core, used in so-called smooth air gap machines.

As has been understood previously, the invention consists in using the armature core itself to transport the calories in the axial direction towards one of its ends where it transfers them to a heat transfer fluid. This mechanism is highlighted in the example of FIG. 1, where the left side of the machine forms a heat exchanger, the fluid of which circulates radially through the intrinsic slots of the armature.

To do this, the armature core is composed of a large number of thin strips of different types (in the example four types: 1 2 3 4) electrically insulated from one another and glued against each other along their wide faces. , their longitudinal direction being substantially pa¬ parallel to the axis of rotation of the machine and their transverse direction being radial, so as to compose an annular volume. Certain blades 1, 3 are larger in length, this protrusion participating in the function of cooling fin. Their thickness being very thin, it may be necessary to juxtapose them in bundles of N blades, to obtain sufficient rigidity. Similarly, the short blades 2,4 will be assembled in packs of P units, so as to obtain radial slots of suitable thickness. Furthermore, certain blades 1, 2 are narrowed over a certain distance so as to be able to accommodate the armature conductors therein. They will be assembled in bundles of R blades, fulfilling the notch function, while the teeth will be made up of the assembly of Q blades 3,4, devoid of narrowing (note: the width of a notch added to that of a tooth is called "no whorl").

The assembly given in FIG. 4 is a specific illustration which cannot be limiting given the flexibility of choice left by the invention. In particular, one can also imagine constituting an armature core without teeth which allows the conductors to be adjacent: it suffices to eliminate the blades of type 3 and 4. The machine is then of the smooth air gap type, a variant of which embodiment is shown in FIG. 6.

In this case we can interpose between the core and the lower and upper layers of conductors a layer

9 electrically insulating and improving the mechanical characteristics of the assembly, for example a layer of glass fabric impregnated with resin, with fibers crossed diagonally.

In the same way, one can imagine that the conductors of the upper and lower layers of FIG. 4 are not facing direct radial, but that one of the two layers has undergone a rotation of half a turn. This arrangement allows greater phase discrimination, but requires at least one additional type of blade identical to 1 or 2 but narrowed on one side. In most cases, two additional types of blades will be required if the blades are asymmetrical transversely. The very shape of the blades has an impact on the thermal resistance between the windings and the outside. Figure 1 thus shows, for didactic reasons, two types of armature core: one, the outer core, is narrowed to the fin of width ¥, which reduces the mass of magnetic material required ; the other, the inner core, is narrowed only in the magnetic zone of influence of the rotor, which reduces the thermal resistance of the blade segment located under the winding head. It would of course be possible for the blades to be of constant width, for reasons of simplicity of cutting, for example.

It should be noted that an adequate shape of the blades makes it possible to minimize cutting losses. We will endeavor to make the blades juxtaposable side by side or head to tail, as in the case for example of Figures 1, 3 and 6. The only losses that remain then are possibly due to folding chamfers like the end of the blade of figure 6. It is also possible to cut two or more types of blades on the same sheet metal tape. Thus the blade 2 fits perfectly on the blade 1 when it is next to it taped head to tail and just repeat this couple on '-. all the length of the ribbon.

Most modern magnetic materials exhibit an anisotropy of their characteristics, acquired for example during annealing in the field or during rolling at a defined temperature. This is particularly the case with oriented crystal sheets, called GOSS texture sheets, the characteristics of which in the direction of rolling are significantly improved. It is therefore necessary, when possible, to orient the blades properly so as to benefit from the lowest hysteresis losses in the transverse direction. A 3 or more factor improvement in permeability and hysteresis losses can thus be obtained, combined with an increase in saturation induction.

The flat blades can only be imperfectly placed against one another because of the difference which exists between the interior and exterior radii of the armature core. There is then created a clearance between the blades which will be maximum on the external periphery. This play can be easily filled with the adhesive assembling the blades, but it has a magnetically harmful role in reducing the apparent permeability of the core. This phenomenon can be compensated for by charging the adhesive with a high percentage of magnetic powder particles, the size and type of the particles affecting the magnetic permeability and the induction of saturation of the compound, the latter preferably being greater than or equal to the induction of work in the air gap.

It may be wise to make each type of blade from a specific material which is more particularly suited to the role of the blade. Thus the blades extended by a blade will benefit from being made of an alloy with high thermal conductivity, for example an Iron-Silicon-Alumunium alloy, while the short blades would be ferromagnetic powder compressed or agglomerated in a binder, for very low hysteresis losses. Since the profile of these latter is not necessarily of constant thickness, it is then possible to easily compensate for the variable play between the blades. Whatever their nature, the thermal resistance of the blades can be reduced by the deposition, on one side o on both, of a film highly conductive of heat, such as copper or aluminum, or recent base compounds graphitized carbon fibers. This deposit can concern the entire surface of the blade or only a limited area, such as for example the surface of the fin.

The mechanical resistance of the blades can be increased if their profile is not planar but curved transversely. This form can for example be raw molding or realized with the press after cutting from a sheet. These profiles, of which several indentations 8 are proposed in FIG. 5 by way of nonlimiting examples, can extend over the entire length of the blades or be restricted to a particular area.

The final deposition of an optional insulating layer 7 allows an improvement in the mechanical strength of the armature assembly, in particular in torsion. It should be noted that this construction makes it possible without difficulty to make slightly frustoconical armature shapes, provided that the longitudinal axis of the blades is inclined.

All of these improvements provide the desired benefits, namely:

- a very low thermal resistance between the armature and the outside of the machine, provided by the absence of multiple insulation junctions encountered in the case of an axial stacking of sheets and improved by immersed proximity ¬ diate of the heat exchanger which is also an integral part of the armature core. - Significantly reduced hysteresis losses, the blades being used in their privileged magnetic direction at all points of the armature core.

It will also be noted that the loss of material, when there is a cut, can be made almost zero by an appropriate shape of the blades, which represents a significant saving.

The invention applies in particular to annular armatures of dynamo-electric machines.

Claims

CLAIMS 1- Annular armature core 5 of a dynamo-electric machine with a radial gap, characterized in that it is made up of a multiplicity of thin blades 1,2,3,4, made of magnetic conductive material heat, electrically isolated from each other and juxtaposed circularly by bonding along their wide faces so that their longitudinal direction is substantially parallel to the axis of rotation of the machine and that their transverse direction is radial, the said blades having one part in packs of N and P blades alternately, the N blades 1,3, having a longer end W in the form of a fin and the P blades 2,4, delimiting radial slots 6 through which a fluid can circulate coolant, said blades being organized on the other hand by alternating packets of Q blades 3,4, performing the function of teeth, and by packets of R narrowed blades 1,2, realizing the function of notches receiving drivers induced, NPQ and R being natural integers not reaching 0 except Q in the case of a smooth air-gap core, the core and coil assembly can be covered on its internal and external surfaces with an insulating layer 7 three-fold and tenacious mechanically.

2- armature core according to the preceding claim, characterized in that, when Q is equal to zero and the core is smooth, an electrically insulating and mechanically insulating layer 9 is inserted between the internal and external faces of the core and the winding layers.

3- armature core according to any one of the preceding CLAIMS, characterized in that the conductors of the upper and lower faces of the core are not facing the exact radial direction but offset by half a turn, which then usually requires 6 different shapes of blades instead of 2 or 4.

4- Armature core according to any one of the preceding claims, characterized in that the shape of the blades allows them to be juxtaposed side by side or head to tail, so that the cutting of the blades only creates very little loss of material. 5- Armature core according to any one of the preceding claims, characterized in that the transverse direction of the blades is the direction of lower hysteresis losses, when the material used is magnetically anisotropic, for example by cutting the blades so that their transverse direction is parallel to the direction of lami¬ nage, when the blades are from laminated sheets.

6- Armature core according to any one of the preceding claims, characterized in that the adhesive assembling the blades is loaded with a magnetic powder, the resulting compound preferably having a higher or equal induction of saturation to the induction of work in the air gap of the machine.

7- Armature core according to any one of the preceding claims, characterized in that certain types of blades are made of magnetic powder agglomerated in a binder or by compression, their profile ensuring minimal play between adjacent blades.

8- Armature core according to any one of the preceding claims, characterized in that certain types of blades are covered on one or two sides, in an area which can be restricted, in particular the fin area, a film of material with high thermal conductivity, such as copper or aluminum. 9- Armature core according to any one of the preceding claims, characterized in that the blades are rigidified by a transverse hollow imprint 8 which may not extend over the entire length of the blade.

10- Armature core according to any one of the preceding claims, characterized in that the longitudinal axis of the blades is slightly oblique so that the armature has a shape of frustoconical revolution.