GB2363005A

GB2363005A - Salient pole structure to mount windings

Info

Publication number: GB2363005A
Application number: GB0109354A
Authority: GB
Inventors: Colin Edward Tindall
Original assignee: Queens University of Belfast
Current assignee: Queens University of Belfast
Priority date: 2000-04-13
Filing date: 2001-04-17
Publication date: 2001-12-05
Also published as: GB0008973D0; GB0109354D0

Abstract

Salient rotor poles having a pole body 20 and an end portion 24 integral with the body have the end portion 24 extending in a circumferential direction to overhang one side of the pole body, the overhang 26 defining a coil-restraining shoulder. This design allows pre-wound coils 22,22a to be fitted over the pole by fitting one side of each of the coils under the coil restraining shoulder and rotating the other side of the coil into position on the pole.

Description

2363005 1 1 "%Electrical Machine Rotor" 2 The present invention relates to

improved rotors for 4 electrical machines. The invention is particularly, but not exclusively, applicable to alternators and 6 synchronous motors. 7 8 9 Whilst the invention will be discussed with particular reference to alternators, it will be understood that it is equally applicable at least to synchronous motors.

11 12 13 The rotors of most alternators are of salient pole 14 construction, as illustrated in Fig.1 of the is attached drawings, the excitation coils (field

16 coils) being wound around the salient poles. in the 17 majority of such machines (and exclusively in the 18 case of small machines; i.e. those with ratings up 19 to about 2 MVA), the rotor has a laminated construction, the gauge of the laminations varying 21 according to factors such as the rating, number of 22 poles, and application. The laminated construction 2 1 is adopted primarily for manufacturing convenience, 2 but also has technical benefits such as reduction in 3 iron losses if the machine is subjected to 4 unbalanced or non-linear loads.

Fig. 1 shows a transverse cross section through a typical salient-pole rotor, having four poles 10, each with an associated coil 12. This also illustrates the shape of the laminations from which the rotor core is constructed. The poles 10 include integral, enlarged end portions 14 (,, pole shoes") having arcuate, convex outer surfaces 16 and defining shoulders 18 which restrain centrifugal movement of the coils 12. A major problem with conventional rotors of this type is that the coils 7 8 9 10 11 12 13 14 15 16 12 have to be wound in situ on the rotor poles 10 17 after construction of the rotor core, which usually 18 includes a damper cage (or amortisseur winding).

19 This is a time-consuming and costly process, since, 20 in order to wind each coil, the rotor has to be 21 rotated about an axis at right angles to its shaft 22 and the coil conductors guided carefully around each 23 pole in turn to form the required number of multi- 24 turn coils. The winding process becomes increasingly difficult as the number of poles 26 increases.

27 28 Arrangements have been proposed which allow pre- 29 wound coils to be fitted to conventional rotor cores 30 such as that of Fig. 1. However, such arrangements 31 all entail an increase in the overall length of the 3 rotor and an increase in the volume of the copper coils.

7 1 2 3 4 It is an object of the present invention to provide 5 a rotor construction which enables the use of pre- 6 wound coils without compromising the performance of the rotor and/or without significantly increasing the overall dimensions of the rotor.

8 9 10 11 12 In accordance with a first aspect of the invention, there is provided an electrical rotor core having a plurality of salient poles, each of said poles comprising a pole body and an integral end portion which is extended in a circumferential direction to overhang one side of the pole body, thereby defining a coil-restraining shoulder.

13 14 15 16 17 18 Preferably, the surface of said shoulder and the 19 adjoining side surface of the pole body together 20 have a generally concave configuration.

21 22 23 24 25 26 27 28 29 30 31 32 Preferably, the other side surface of each pole opposite said shoulder has a generally convex configuration.

In certain embodiments, said shoulder and adjoining side surface of one pole and said other surface of an adjacent pole together define a channel having a part circular transverse cross section.

In accordance with a second aspect of the invention, there is provided an electrical rotor comprising a 4 rotor core in accordance with the first aspect of the invention and a plurality of pre-wound coils 1 2 3 located on the poles of said rotor body such that 4 one side of each of said coils lies under said shoulder of one of said poles.

6 7 Preferably, the rotor further includes inter-polar 8 restraining means for retaining said coils in 9 position.

11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 In certain embodiments, the number of coils is equal to half the number of poles.

In other embodiments, the number of coils is equal to the number of poles. In these cases, a channel defined between a pair of adjacent poles accommodates one side of each of a pair of coils, said channels and said coils having complementary transverse cross sections.

In accordance with a third aspect of the invention, there is provided an electrical machine including a rotor in accordance with the second aspect of the invention.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic transverse cross section of a conventional fourpole rotor; 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 two pre-wound coils 22. The poles each comprise a 23 pole body with an integral end portion (pole shoe) 24 24 having a generally convex outer surface 26. 25 Unlike conventional rotors, the poles 20 have an 26 asymmetric shape, defining a coil- retaining shoulder 27 28 only at one side of each pole 20. This shape 28 allows the pre-wound coils to be fitted over the 29 poles by engaging one side 30 of the coil with the 30 shoulder 28 as shown at 22a and rotating the coil 31 about that side into position on the pole 20. 32 Fig. 2 is a schematic transverse cross section of a first embodiment of a rotor in accordance with the present invention; Fig. 3 is a schematic transverse cross section of a second embodiment of a rotor in accordance with the present invention; Fig. 4 is a schematic transverse cross section of a third embodiment of a rotor in accordance with the present invention; and Fig. 5 is a schematic transverse cross section of a fourth embodiment of a rotor in accordance with the present invention.

Referring now to the drawings, Fig. 2 shows a first embodiment of a rotor in accordance with the present invention. The rotor may be of conventional laminated construction. In this embodiment, the rotor core has four poles 20, adapted to accommodate 6 1 Accordingly, one side of the coil 22 is restrained 2 against centrifugal movement by the shoulder 28' 3 whilst the other side 32 lies in a channel formed 4 between the other side of the pole 20 and the 5 shoulder 28 of the adjacent pole 20. It has been 6 found that the other side 32 of each coil 22 can be 7 restrained satisfactorily against centrifugal movement by means of inter-polar clamps or wedges 34, suitably in combination with conventional coilend restraints 35.

8 9 11 12 As can he seen from the drawing, the inner surface 13 of the shoulder 28 is generally concave and the 14 opposite side surface of the pole 20 is generally convex. The shape of these generally concave and 16 convex surfaces in this and the following 17 embodiments may be defined by smooth curves or 18 straight line segments or combinations of curves and 19 straight line segments. In this embodiment, the shapes of adjacent poles differ slightly from one 21 another, to facilitate the rotation of the coils 22 into position, but diametrically opposed poles have 23 identical shapes.

24 26 27 28 29 31 32 It has also been found that the asymmetric shape of the poles 20 does not adversely affect the rotor performance to any significant degree. The production and assembly of the rotor laminations can be performed by conventional means, requiring only a replacement punch and die for forming the laminations.

7 1 The embodiment of Fig. 2 has four poles 20 and two 2 coils 22. Fig. 3 shows a somewhat similar rotor 3 core having four identical poles 40 with shoulders 4 48 and four pre-wound coils 42a, 42b, 42c and 42d. 5 In order to allow the four coils 42a-d to be fitted 6 and accommodated by the rotor core, the coils each 7 have a semi-circular cross section and the shoulders 8 48 and adjacent side walls of the poles 40 define a 9 complementary part-circular channel, allowing the 10 coils 42a-d to be rotated into position as indicated 11 at 42e. 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 The pairs of coils are again restrained against centrifugal movement by means of inter-polar clamps or wedges 54 between each pair of adjacent poles, suitably in combination with conventional coil-end restraints 55.

Fig. 4 shows a further embodiment of a rotor which is similar in principle to that of Fig. 3, with 8 identical poles 60 adapted to accommodate eight semicircular section coils 62a-h. The pairs of coils would again be restrained against centrifugal movement by means of inter- polar clamps or wedges (not shown) between each pair of adjacent poles, suitably in combination with conventional coil-end restraints 64.

Fig. 5 shows still another embodiment of a rotor, similar in principle to Figs. 3 and 4, having six poles 70 with a modified shape to accommodate pairs 8 1 of complementary non-semicircular section coils 72 (in this case having a trapezoidal cross section).

7 11 12 13 14 is 16 17 18 19 20 21 22 23 2 3 4 It will be understood that rotors having more than 5 four poles could also be made similar to the 6 embodiment of Fig. 2; i.e. having a number of coils equal to half the number of poles.

8 9 Improvements, variations and modifications may be incorporated without departing from the scope of the invention 9 1 2 3 4 5 6 7 8 9 11 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Claims

1. An electrical rotor core having a plurality of salient poles, each of said poles comprising a pole body and an integral end portion which is extended in a circumferential direction to overhang one side of the pole body, thereby defining a coilrestraining shoulder.

2. An electrical rotor core as claimed in Claim 1, wherein the surface of said shoulder and the adjoining side surface of the pole body together have a generally concave configuration.

3. An electrical rotor core as claimed in Claim 1 or claim 2, wherein the other side surface of each pole opposite said shoulder has a generally convex configuration.

4. An electrical rotor core as claimed in any preceding Claim, wherein said shoulder and adjoining side surface of one pole and said other surface of an adjacent pole together define a channel having part circular transverse cross section.

5. An electrical rotor comprising a rotor core accordance with any of claims 1 to 4 and a plurality of pre-wound coils located on the poles of said rotor body such that one side of each of said coils lies under said shoulder of one of said poles.

6. An electrical rotor as claimed in Claim 5, 2 wherein the rotor^further includes inter-polar 3 restraining means for retaining said coils in position.

4 5 6

7 8 9 10 12 13 14 is 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 7. An electrical rotor as claimed in Claim 5 or Claim 6, wherein the number of coils is equal to half the number of poles.

8. An electrical rotor as claimed in Claim 5 or Claim 6, wherein the number of coils is equal to the number of poles.

9. An electrical rotor as claimed in Claim 8, wherein a channel is defined between a pair of adjacent poles to accommodate one side of each of a pair of coils, said channels and said coils having complementary transverse cross sections.

10. An electrical machine including a rotor as claimed in any of Claims 5 to 9.

11. An electrical rotor core, substantially as hereinbefore described with reference to the accompanying drawing.

12. An electrical rotor, substantially as hereinbefore described with reference to the accompanying drawing.

2 3 4 5 6 7 8

13. An electrical machine, substantially as hereinbefore described with reference to the accompanying drawing.