WO2018166930A1

WO2018166930A1 - Electronically commutated electrical machine

Info

Publication number: WO2018166930A1
Application number: PCT/EP2018/055993
Authority: WO
Inventors: Steven Andrew Evans
Original assignee: Robert Bosch Gmbh
Priority date: 2017-03-16
Filing date: 2018-03-12
Publication date: 2018-09-20
Also published as: CN110383634A; EP3596803A1; DE102017204382A1; CN110383634B

Abstract

The invention relates to a stator assembly (2) for an electrical machine, comprising: a cylindrical stator yoke (21), which has main stator teeth (22a) and spacing stator teeth (22b) protruding therefrom, a plurality of stator tooth groups (G) each having a plurality of adjacent main stator teeth (22a) being separated from each other by means of a spacing stator tooth (22b) in each case; a plurality of separate winding units (28), each of which has a number of phase conductors, each of which has one or more phase coils (26), each winding unit (28) being associated with one of the stator tooth groups (G) and being arranged thereon.

Description

description

title

Electronically commutated electrical machine

Technical area

The invention relates to electronically commutated electrical machines, in particular electrical machines with measures for increased fault tolerance.

Technical background

Electronically commutated electrical machines, in particular permanent magnet-excited electrical machines, can be designed for increased robustness against electrical faults with a plurality of separate winding units. The Wcklungseinheiten each comprise separate phase strands, each with one or more phase coils. The separate weighers are each driven by separate power modules to provide high electrical isolation, thereby providing a high degree of robustness against faults. This is especially true for electrical machines in which the phase strands of the individual Wcklungseinheiten not distributed, but are arranged in segments on a stator of the electric machine.

By virtue of the arrangement on the stator, the separate polyphase dicing units are electrically isolated, but not magnetically and thermally isolated from one another, whereby the fault tolerance of the electric machine is limited to short circuit faults within one of the dewatering units. In addition, an uncontrollable short-circuit current in one of the faulty reject units may generate a magnetic flux that is in one of the adjacent faultless ones Winding units coupled and the control or regulation of the phase currents in the error-free winding unit difficult. This can potentially endanger the operation of the electrical machine.

Furthermore, a short-circuit current can cause high ohmic losses in the faulty winding unit, whereby the thermal integrity of the adjacent fault-free Wcklungseinheiten can be affected due to lack of thermal insulation between the winding units.

From the prior art, a three-phase electric machine is known, which have four Wcklungseinheiten, each associated with a quarter segment of the stator assembly. The electric machine has twelve slots and eight rotor poles, so that the respective weigher units are each formed with three stator teeth, so that each of the stator coils is assigned to a phase. The four individual units are powered by four separate three-phase power modules in the form of three-phase converters to provide the electrical insulation between the winding units necessary for fault tolerance. However, in this machine topology, the four winding units are not magnetically and thermally isolated from each other, and phase strands of adjacent winding units lie in a common stator slot so that a short circuit between the phase strings of two weeder units can result in the failure of two of the weighers.

It is an object of the present invention to provide a fault-tolerant, electronically commutated electrical machine in which the robustness against errors in one of the wetting units is improved.

Disclosure of the invention

This object is achieved by the stator assembly for an electric machine according to claim 1 and by the electric machine according to the independent claim. Further embodiments are specified in the dependent claims.

According to a first aspect, there is provided a stator assembly for an electric machine, comprising:

a cylindrical stator yoke having main stator teeth and spacer stator teeth projecting therefrom, wherein a plurality of stator teeth groups of a plurality of mutually adjacent main stator teeth are separated from each other by a spacer stator tooth;

a plurality of separate winding units each having a number of phase strands, each having one or more phase coils, wherein the winding units are each associated with one of the stator tooth groups of the stator assembly and arranged thereon.

An idea of the above stator arrangement is to arrange several separate Wecklungs- units each having a number of phase strands, each having one or more phase coils, in each case in segments of stator tooth groups of the stator assembly, so that the separate Wcklungseinheiten adjacent to each other are provided on the stator. The Wecklungseinheiten do not overlap, so that phase coils of different Wcklungseinheiten are not arranged in a common Statornut. Therefore, in the event of an electrical short in one of the weeding units, the electrical integrity of the other winding units is not impaired. Between the stator tooth groups associated with the individual winding units, a spacer stator tooth is provided, which has a geometry deviating from the stator teeth of the stator tooth groups. In this way, an improved thermal and magnetic decoupling can be achieved.

Furthermore, the width of the tooth shanks of the spacer stator teeth may be equal to or greater than the width of the main stator teeth. In particular, the Abstandstatorzähne and the Hauptstatorzähne may each have tooth tips, which are widened with respect to the toothed shaft in the circumferential direction. It can be provided that in an electrical machine having a pole pair number O and a number N of separate winding units, a distance stator tooth angle CIST, ie the angular range covered by one of the spacer stator teeth, is 360 ° (1 / N-1/0) ,

Further, in an electric machine having a pole pair number O, a phase number P and a number N of separate weeding units, a main stator tooth angle CIMT, i. the range of angles covered by one of the main stator teeth is 360 ° / (O P).

It can be provided that in an electric machine with a pole pair number of 5, four separate winding units and a phase number of 3, a distance stator tooth angle CIST, i. the angular range covered by one of the spacer stator teeth corresponds to 1/2 ap, where ap corresponds to a pole angle of a rotor pole.

According to one embodiment, in an electric machine having a pole pair number of 5, four separate weeding units and a number of phases of 3, a main stator tooth angle CIMT, i. the angular range covered by one of the main stator teeth corresponds to 2/3 ap, where ap corresponds to a pole angle of a rotor pole.

According to a further aspect, an electric machine with the above stator arrangement and a rotor with rotor poles is provided.

Furthermore, the pole pair number of the rotor can correspond to five.

According to a further aspect, a motor system with the above electrical machine and with power modules is provided which are each designed to drive one or more of the winding units.

Furthermore, the power modules can be designed or controllable in order to drive the winding units with a phase offset of the phase currents. Brief description of the drawings

Embodiments are explained below with reference to the accompanying drawings. Show it:

FIG. 1 is a cross-sectional view through an electronically commutated electrical machine;

FIG. 2 shows a section through the electric machine of FIG. 1 for illustrating the dimensioning of the stator teeth of the stator arrangement of the electric machine;

Figure 3 is a schematic representation of a control of the electric machine with separate power modules;

FIG. 4 shows a diagram for illustrating the profiles of the phase currents of one of the winding units; and

Figure 5 is a representation of the torque curve over the angle of rotation.

Description of embodiments

FIG. 1 shows a schematic cross-sectional representation through an exemplary permanent magnet-excited electric machine 1. The electric machine has a stator arrangement 2 and a rotor 3. The stator assembly 2 is formed substantially cylindrical and has a likewise cylindrical inner recess 4, in which the rotor 3 is arranged rotatably.

The stator assembly 2 has a cylindrical stator yoke 21 from which evenly spaced stator teeth 22 project inwardly. In the present Guidance example, 16 stator teeth 22 are provided. The stator teeth 22 include main stator teeth 22a and spacer stator teeth 22b. Each of the stator teeth 22a, 22b is provided with a toothed shaft 23 projecting from the stator yoke 21, at the inwardly projecting end thereof a tooth tip 24 is arranged. The tooth heads 24 represent over the width of the tooth shanks 23 protruding tooth head portions which widen the stator tooth 22 at its end, and form the cylindrical contour of the inner recess. 4

The rotor 3 is provided with a rotor body 31 and with the rotor poles 32 forming permanent magnets 33. The permanent magnets 33 are provided as surface-mounted magnets which have a contouring, for example a judge contour or the like, on their surfaces facing the stator teeth. In alternative embodiments, the rotor 3 may also be formed with buried permanent magnets.

According to the embodiment, the electric machine 1 has sixteen stator teeth 22 and ten rotor poles 32. The sixteen stator teeth 22 include four stator teeth groups of adjacent main stator teeth 22a, each separated by one of the spacer stator teeth 22b.

The main stator teeth 22a of a stator tooth group G are each wound with a stator coil 26, which are assigned to a phase or a phase strand. The stator coils 26 of one of the stator tooth groups G form a winding unit 28. The stator coils 26 of a stator tooth group G are each assigned to different phases, so that stator coils 26 for three phases are arranged on the stator teeth 22a of a stator tooth group G in the exemplary embodiments shown. The distance stator tooth 22b between two adjacent stator tooth groups G allows the immediately adjacent stator coils 26 of two adjacent stator tooth groups G not to be in the same stator slot 25, so that short circuits between the stator coils of different winding units can not occur.

FIG. 2 shows, in a detailed view of the electric machine 1, the dimensioning of the spacing stator tooth 22b, the main stator teeth 22a and the rotor poles 32 illustrates. The main stator tooth width WMT, ie the width of the main stator teeth 22a in the circumferential direction, is equal to or smaller than the distance stator tooth width WST, ie the width of the spacer stator teeth 22b in the circumferential direction (this is not drawn to scale in FIGS. 1-3):

WMT <= WST

This makes it possible to avoid magnetic saturation in the distance stator tooth 22b during operation of the electric machine.

The stator teeth 22 are not uniformly spaced from each other with their center axis and form stator slots 25 therebetween.

In particular, main pitches OH between the center axes of the main stator teeth 22a are larger than the pitch pitches CIA between the center axis of a main stator tooth and the center axis of an adjacent spacer stator tooth 22b. In the present embodiment, the main tooth distances OH (angular distance) are 24 ° and pitch distances CIA 21 °. In general, α _Η = 360 (N (P + 1)) + ΔΑ

a _A = 360 (N (P + 1)) - ΔΑ (Ρ-1) / 2 corresponds to a number N of separate winding units and P corresponds to the phase number of each of the winding units. ΔΑ corresponds to a selectable difference distance which can be selected in the range up to 10% of 360 N.

Furthermore, the main electric stator angle CIMT, i. the Wnkelbe- area is covered by one of the main stator teeth 22a, measured between the centers of the slot openings of the respective main stator tooth 22a defining stator slots 25, 120 ° electrical position angle, the electrical attitude angle is defined as 360 ° by the number of pole pairs of the rotor 3.

Furthermore, the following applies: CIMT = 2/3 cip, where cip corresponds to the rotor pole angle, ie the angle range which covers a rotor pole. Furthermore, the distance stator tooth angle CIST, ie the angle range which is covered by one of the spacer stator teeth 22b, measured from the centers of the slot openings of the adjacent stator slots 25, should correspond to 90 ° electrical contact position, which corresponds to one half of a rotor pole angle cip:

Generally, for an electric machine having a pole pair number of O, a number N of separate winding units for the pitch stator tooth angle CIST a _ST = 360 ° (1 / N - 1/0).

Accordingly, for the mechanical main stator tooth angle CIMT, one of the main stator teeth 22a

QMT = 360 ° / (O P), where P corresponds to the number of phases of the electric machine.

3 shows a schematic representation of a control of the electric machine of Figure 1 is shown. It can be seen that the three phases of each of the winding units 28 are driven by a separate power module 5. In this case, the phase strands of each of the winding units 28 can be connected either in a star or a polygon circuit.

The winding units, which are diametrically opposed to each other, are driven by three-phase drive currents, as shown, for example, in the diagram of FIG. 4, which are offset from one another by 90 ° from the drive currents of a drive for the other two weeding units 28, which are likewise opposite one another , For example, the following current profiles over the electrical position angle Θ can be provided for the control of the weeding units W1 and W3: i _A = I sin (ö) i _B = I sin (0 + 120 °)

i _c = I sin (Ö - 120 °) wherein the current waveforms of the winding units W2 and W4 are controlled as follows. ί _Α = I sin (0 + 90 °)

i _B = I sin (0-150 °)

i _c = I sin (0 - 30 °)

FIG. 5 shows the normalized torque curve over a range of electrical position angles for the cases in which only the winding units W1 and W3 and only the reject units W2 and W4 are driven, and in the case where all four winding units are offset from each other by 90.degree Phase flow can be controlled. As a result, the torque ripple of the electric machine can be significantly reduced, for the present embodiment from 13.5% to 1, 9% of the average torque.

Claims

claims

A stator assembly (2) for an electrical machine, comprising:

a cylindrical stator yoke (21) having main stator teeth (22a) and spacer stator teeth (22b) projecting therefrom, a plurality of stator tooth groups (G) being separated from a plurality of adjacent main stator teeth (22a) by a spacer stator tooth (22b), respectively;

a plurality of separate winding units (28), each having a number of phase strands, each having one or more phase coils (26), wherein the winding units (28) are each associated with one of the stator tooth groups (G) and arranged thereon.

The stator assembly (2) according to claim 1, wherein the width of tooth shanks (23) of the spacer stator teeth (22b) is equal to or greater than the width of tooth shanks (23) of the main stator teeth (22a).

The stator assembly (2) according to claim 2, wherein the spacer stator teeth (22b) and the main stator teeth (22a) each have teeth heads (24) which are widened circumferentially with respect to the tooth shanks (23), in particular the tooth head projection in circumferential direction at the main stator teeth (22a) is larger than the spacer stator teeth (22b).

The stator assembly (2) according to any one of claims 1 to 3, wherein a pole pair number O and a number N of separate weeding units have a pitch stator tooth angle CIST, i. the angular range covered by one of the spacer stator teeth (22b) is 360 ° (1 / N - 1/0).

5. stator arrangement (2) according to one of claims 1 to 4, wherein at a pole pair number O, a phase number P and a number N of separate Wcklungseinheiten (28) A main stator tooth angle CIMT, that is, the angular range covered by one of the main stator teeth (22b) is 360 ° / (O * P).

The stator assembly (2) according to any one of claims 1 to 5, wherein the main teeth pitches QH between the center axes of the main stator teeth (22a) are larger than the pitch pitches CIA between the center axis of a main stator tooth (22a) and the center axis of an adjacent spacer stator tooth (22). 22b), and in particular the main pitches QH (angular distance) 24 ° and the pitch spacing (Wnkelabstand) CIA 21 ⁰ .

7. Electrical machine (1) with a stator assembly (2) according to one of claims 1 to 6 and a rotor (3) with rotor poles.

8. An electric machine (1) according to claim 7, wherein at a pole pair number of 5, four separate weeding units (28) and a phase number of 3, a pitch stator tooth angle CIST, i. the angle range covered by one of the spacer stator teeth (22b) corresponds to 1/2 ap, where ap corresponds to a pole angle of a rotor pole.

An electric machine (1) according to any one of claims 7 to 8, wherein at a pole pair number of 5, four separate weeding units and a phase number of 3, a main stator tooth angle CIMT, i. the range of angles covered by one of the main stator teeth corresponds to 2/3 ap, where ap corresponds to a pole angle of a rotor pole.

10. Motor system with an electric machine according to one of claims 7 to 9 and with power modules (5) which are each designed to control one or more of the winding units (28).

1 1. An engine system according to claim 10, wherein the power modules (5) are formed or are controllable to drive the Wecklungseinheiten (28) with a phase offset of the phase currents.