Stator

Abstract

A stator having slots separated by stator teeth, into which shaped bars, formed from a plurality of individual wires, are deployed, wherein in each case sidewalls of a stator tooth bounding adjacent slots in a region of the shaped bars run essentially parallel to one another.

Claims

1. A stator for an electrical machine, the stator comprising: a plurality of teeth disposed along a circumference of the stator, each of the teeth including sidewalls that run essentially parallel to one another, sidewalls of adjacent teeth separating the stator into a plurality of slots along the circumference of the stator; and at least two shaped bars disposed one above another in each of the slots, the shaped bars having different shapes and approximately same cross-sectional areas, each shaped bar of the at least two shaped bars having a length and including an arrangement of two flat layers disposed one above another as viewed in a radial direction of the electrical machine, the arrangement formed from a plurality of individual wires twisted with each other and grouted such that each wire of the individual wires lies at a surface along the length of each shaped bar, the at least two shaped bars being electrically insulated one from another in their course through each of the slots, and the at least two shaped bars being at least indirectly serially connected with one another.

2. The stator as claimed in claim 1, wherein the at least two shaped bars are disposed against the sidewalls of each of the teeth.

3. The stator as claimed in claim 1, wherein the at least two shaped bars have trapezoidal cross sections.

4. The stator as claimed in claim 1, wherein the at least two shaped bars are cold formed by rolling.

5. The stator as claimed in claim 4, wherein the at least two shaped bars comprise pre-bent end portions.

6. The stator as claimed in claim 1, wherein at least one of the at least two shaped bars comprises at least two partial bars lying closely one against another, the at least two partial bars connected to form the at least one of the at least two shaped bars.

7. The stator as claimed in claim 1, wherein a length of each of the slots of the stator is a whole number multiple of a lay length of at least one wire of the plurality of individual wires.

8. The stator as claimed in claim 1, wherein a stator pole length is between 50 and 120 mm, and stator slot cross section is between 80 and 150 mm.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The reference symbol list is a component of the disclosure. The figures are described in a connected and comprehensive manner. The same reference symbols denote the same parts, while reference symbols with different indices specify parts with the same or similar functions.

(2) In the figures:

(3) FIG. 1 shows a motor with a stator designed in accordance with the invention;

(4) FIG. 2 shows in a schematic representation of the flux permeating the stator in the saturation region;

(5) FIG. 3 shows a detail scrap section of an inventive stator;

(6) FIG. 4 shows the design of a stator tooth with adjacent slots, of which one is already occupied with shaped bars;

(7) FIG. 5 shows a first group of coil elements;

(8) FIG. 6 shows a second group of coil elements;

(9) FIG. 7 shows the first and second groups of coil elements assembled to form a complete phase; and

(10) FIG. 8 shows a shaped bar in detail;

(11) FIG. 9 shows an end of a preferred embodiment of a shaped bar in greater scale; and

(12) FIG. 10 shows a section of one end of the stator with a further advantageous embodiment of the shaped bars inserted into a slot of the stator.

DETAILED DESCRIPTION

(13) FIG. 1 shows an electric motor 5 with a stator 1 and a rotor 2 surrounded by the stator 1 in cross-section, and normal to the rotor axis of rotation. The stator 1 includes along its circumference a multiplicity of slots 8, which are separated from one another by stator teeth 6 (FIGS. 3 and 4). In the present example, the motor 5 takes the form of a rotating field machine with 3 phases and 6 poles. In total, the windings are distributed onto 54 slots in this example. Nine slots 8 are therefore provided per pole. Two shaped bars 3, 4 that are insulated from one another are in each case deployed in each slot 8 (FIGS. 3 and 4). The shaped bars 4 that face towards the rotor 2 form the upper layer and are also called upper bars. The shaped bars 3 that sit deeper in the slots 8 and face away from the rotor 2 form the lower layer and are called lower bars.

(14) FIGS. 3A and 3B show in each case a segmental section of an inventive motor 5 with different magnetic field distributions. In the left-hand figure of FIG. 3A, one sees the field lines above a magnetic pole, while the right-handed figure of FIG. 3B shows the field lines in the centre of a magnetic pole.

(15) In principle, the same operating points are being represented in the same motor.

(16) Both sidewalls 7 of a stator tooth 6, which demarcate adjacent slots 8, in the region of the shaped bars 3, 4 run essentially parallel to one another (FIG. 4). As a result, as may be seen from the flux lines that have been plotted, an almost homogeneous magnetic loading of the stator material ensues, in particular, in the region of the stator teeth 6. Almost all regions of a flux path have a homogeneous flux density. As a further consequence, this leads to the fact that in the event of a further increase of the flux, the stator regions permeated by the flux enter into saturation almost uniformly. The parallel flux lines along the stator tooth 6 are a direct consequence of the parallel sidewalls 7 of the stator tooth 6. A yoke height of the stator 1 is designated as reference no. 9.

(17) FIGS. 2A and 2B show the saturation curves for two different types of motors: on the left-hand side of FIG. 2A in mains network operation; and on the right-hand side of FIG. 2B in inverter operation. Along the vertical axis is plotted the flux running in the air gap between stator 1 and rotor 2, while along the horizontal axis is the torque. The left-hand type of motor of FIG. 2A corresponds to a conventional motor. The right-hand type of motor of FIG. 2B corresponds to the invention. In the case of this inventive type, one detects in contrast, a very sharply bounded transition into the saturation region. This shows the sudden saturation characteristic of motors of a build type. This is advantageous since the motor thus operates faster in the optimal power region. This ensues primarily on account of the inventive stator section, which in accordance with the invention has been optimized for inverter operation. For this, one wants a very sharply bounded transition (right-hand diagram of FIG. 2B) into the saturation region (as highlighted by the circle). This delivers a high torque, at the same time with less excitation power supplied via the stator 1. This requires that all regions of the stator 1 permeated by the flux are equally highly controlled. In accordance with the invention, this is achieved by parallel contours in the stator tooth region. In order to achieve further optimisation, the slots 8 of trapezoidal design, by virtue of the design of the stator teeth 6, are filled in the best possible manner with shaped bars 3, 4.

(18) In the version represented, the shaped bars 3, 4 are designed such that in each case they sit closely against the opposing sidewalls 7 of the slot 8 formed from two adjacent stator teeth 6. This can also be seen in FIG. 4 in detail. In order to fill in the best possible manner the slots 8 formed by the stator teeth 6, which in each case have sidewalls 7 aligned parallel to one another, the shaped bars 3, 4 in each case have a trapezoidal cross-section. As can be seen in FIG. 4, the cross-section of the stator teeth 6 can diverge underneath the shaped bars 3 and 4. However, what is important for the invention is the fact that the two sidewalls 7 of the stator tooth 6 run essentially parallel to one another, at least in the region of the shaped bars 3, 4.

(19) The shaped bars 3, 4, sitting in the slot 8 in different layers, preferably have essentially equal cross-sectional areas, so that the excitation current encounters the same resistance in all shaped bars 3 and 4. That means that the shaped bars 3, 4 have at least approximately the same cross sectional areas, one area being preferably within 90% of the other area. In order that this be possible with the trapezoidal slot cross-sections and the close contact with the stator teeth 6, the shaped bars 3, 4 of the given slot 8 have different shapes. As can be seen in FIG. 4, both shaped bars 3, 4 have a trapezoidal shape, but the side and height relationships of the two trapeziums are different, as a result of which the trapezoidal shapes are different. In geometrical terms, these two trapeziums are neither congruent nor similar.

(20) To illustrate how the shaped bars 3, 4 in the slot 8 are connected with one another, FIGS. 5, 6, and 7 show the windings that belong to one of the three phases. The windings of one phase include a first group of coil elements in accordance with FIG. 5, and a second group of coil elements in accordance with FIG. 6. In FIG. 7, the serial wiring of the groups of coil elements is represented. The shaped bars 3 represented in FIGS. 5, 6, and 7 in strip form are the lower bars, which sit in the lower layer (facing away from the rotor 2) (FIGS. 3 and 4). The shaped bars 4 represented as simple lines are the upper bars, which sit in the upper layer (facing towards the rotor 2) (FIGS. 3 and 4).

(21) The differing representations of the upper and lower shaped bars 4 and 3, respectively, have been selected purely so as to be able to represent shaped bars running one above another in the plane of FIGS. 3 and 4. However, these differences in representation do not mean that the shaped bars 3, 4 are of differing thickness. Also the shape and position of the interfaces between upper and lower bars represented at the respective faces of the stator 1 have no deeper meaning with regard to the present invention. FIGS. 5, 6, and 7 have the sole objective of illustrating the topology and wiring of the individual shaped bars 3 and 4, and thus the course and sense of direction of the windings.

(22) As can be seen in FIGS. 5, 6, and 7, there takes place after each pass through the stator 1, a layer change, i.e., a majority of the connections at the faces of the stator 1 connect an upper bar with a lower bar. The arrows specify the respective sense of winding, the numbers under the arrows the numbering of the slots. In the first group of coil elements in FIG. 5, the windings begin in the lower layer with slot no. 3 and end with slot no. 46, which is connected with the star point (indicated by a leading out arrow). In the second group of coil elements in FIG. 6, the windings begin in the upper layer with slot no. 1 (as indicated by a point) and end with slot no. 12, which is connected with the lower layer of slot no. 3 (FIG. 5). The upper bar of slot no. 1 is connected with the phase connection (as indicated by a point). The windings of the two groups of coil elements are serially connected with one another and along the circumference of the stator have an opposite sense of direction.

(23) The two shaped bars 3, 4 of the slot 8 are electrically insulated from one another in their course through the slot 8, but are serially connected with one another by the multiplicity of windings. The windings of the other two phases are not represented in the interests of clarity, but can be embodied in an analogous manner.

(24) The shaped bars 3, 4 are in each case formed from a multiplicity of individual wires 10 (FIG. 8). These are preferably multiply stranded. This means that in the first instance, a group of individual wires 10 are stranded, i.e., twisted, to form a strand. In a further step, two or a plurality of these strands are then stranded, i.e., twisted, together. In this manner, multiple stranding is obtained. Other stranding cascades are possible.

(25) In FIG. 8, one sees an inventively deployed shaped bar 3, 4 in detail. It includes a plurality of individual wires 10 that are insulated from one another and twisted. At the end 11 of each shaped bar 3, 4, these wires 10 are electrically connected (welded) together. Thus, the above-described conducting loops are formed within a shaped bar 3, 4. The lay length 12 of a twisted individual wire 10 is a length over which a complete rotation (360 mech. degrees) of the wire 10 is distributed about its own longitudinal axis.

(26) As can be seen in FIG. 9, each of the shaped bars 3, 4 in an advantageous embodiment includes at least two layers A, B lying above one another, the layers A, B each including a plurality of individual wires 10, which are twisted with each other and are preferably grouted. Each of the individual wires 10 comes to lie on the surface of the respective shaped bars 3, 4, with the advantage of the ameliorated cooling of the shaped bars 3, 4.

(27) The shaped bars 3, 4 thus formed are subsequently, that is to say, after the stranding process, brought into the inventive trapezoidal shape. It has been shown that cold forming, in particular by a rolling process, has here proved itself in terms of quality and manufacturing costs.

(28) In the course of the shaping the shaped bars 3, 4 during the production process, according to an advantageous variant of such method, the ends of the shaped bars 3, 4 are pre-bent before they are inserted into the slot 8 of the stator 1, in order to make the following step of their wiring more easy. Shaped bars 3, 4 according to such an embodiment are shown in FIG. 10.

(29) To be able to introduce pre-bent shaped bars 3, 4 into the slots 8 more easily, broadened inner ends of the stator teeth 6 are asymmetrical in a manner that results in an essentially flat surface area on one side of the stator tooth 6 and in a broader projection 6a in the direction towards the adjacent stator tooth 6.

(30) Preferably, and as can also be gathered from FIG. 10, both shaped bars 3, 4 include at least two essentially flat partial bars 3a, 3b and 4a, 4b, respectively, which are lying closely one against the other and are connected to form the shaped bar 3 and 4, respectively. In a preferred manner, the thickness of each of the partial bars 3a, 3b, 4a, 4b is not greater than the gap width between the edge of the projection 6a of one stator tooth 6 and the adjacent edge of the adjacent stator tooth 6. Introducing the partial bars 3a, 3b, 4a, 4b into the slot 8 is done through the gap between two adjacent stator teeth 6 in the following order: firstly, the partial bar 3a is introduced, then partial bar 3b followed by partial bar 4a and finally partial bar 4b are inserted. Partial bars 3a and 4a, respectively, are each displaced in a direction oblique to the direction of their insertion, to bring them into a position behind the broader projection 6a of the stator tooth 6. Thus, the respective second partial bar 3b and 4b, respectively, can be introduced into the slot 8 with a straight-direction movement.

(31) The shaped bars 3, 4 in each version are electrically connected with one another at the ends.

(32) A form of connection for the individual shaped bars 3, 4 that is suitable for automotive applications is resistance welding (or thermal fusing).

(33) This form of connection is in fact already deployed in motors in the automotive sector.

(34) However, in the inventive special case, this form of connection is deployed for purposes of connecting the electrical conductors between the respective slots, in contrast to conventional applications, in which, e.g., the phase tappings are connected.

(35) Thus, the difference from conventional applications is that the deflection of the current flow in the winding head is enabled by this form of connection (resistance welding), which is novel for this purpose.

(36) Resistance welding (or thermal fusing) is an option of known art for electrical connections, which in particular finds application in the automotive sector on account of its vibration resistance and thermal shock resistance.

(37) However, a big additional advantage of resistance welding for the present invention is that the stripping of the electrical insulation layer from the respective conductors is also included in the process, and does not have to be undertaken in advance. This is of particular advantage for the new application when connecting the electrical conductors between the respective slots, since it enables a complete connection of all conductors without the need to undertake any significant preparatory treatments. In this manner, the number of steps in the method for the manufacture of the winding can be reduced, as also can the manufacturing costs.

(38) In order to minimise the manufacturing costs further, a continuous multiple rolling process is used.

(39) The invention is not limited to the examples of embodiment represented. It is quite conceivable that the rotor 2 is an external rotor that surrounds the stator 1. The invention is also suitable for rotating field machines of any topology (winding path). Also, more than two shaped bars can sit in one slot.

LIST OF REFERENCE LABELS

(40) 1 Stator 2 Rotor 3 Shaped bar (lower bar) 3a, 3b partial bars 4 Shaped bar (upper bar) 4a, 4b partial bars 5 Motor 6 Stator tooth 6a projection of the stator tooth 7 Sidewalls of a stator tooth 6 8 Slot 9 Yoke height 10 Individual wires 11 End of the shaped bar 12 Lay length in a stranded/twisted shaped bar made up from a plurality of individual wires 10 A, B layers of the shaped bar.