GB2037093A

GB2037093A - Stator assemblies for electrical rotating machines

Info

Publication number: GB2037093A
Application number: GB7938366A
Authority: GB
Original assignee: Jones & Co Ltd W
Current assignee: Jones & Co Ltd W
Priority date: 1978-11-06
Filing date: 1979-11-06
Publication date: 1980-07-02
Also published as: GB2037093B

Abstract

A stator assembly for an electrical rotating machine comprises a stack of laminations (2) and end shields (4 and 6), the laminations and endshields being secured to form a rigid unit by a plurality of longitudinal welds (7). As shown, the welds (7) extend in zig-zag manner between the end shields (4 and 6). The welds may form H shapes (Fig. 2, not shown). In forming the assembly by a plasma welding technique, the stator assembly is mounted in a rotatable support (28, Fig. 5 not shown) and a plasma beam is directed onto the stator and is deflected electromagnetically whilst the stator is rotated. <IMAGE>

Description

SPECIFICATION Improvements in stator assemblies for electrical rotating machines The present invention relates to a stator assembly for an electrical rotating machine.

Conventional machines having a laminated stator and windings, normally have their stacks of laminations secured prior to winding by either bolts and nuts, rivets or axial welds.

End shields are provided on each end of the stack of laminations and these may be either secured by the bolts or separately attached.

In small machines, the provision of bolts and nuts to secure the stator laminations takes up a fair amount of extra space and adds considerably to the weight of the machine.

It is an object of the present invention to overcome partially or wholly the above mentioned disadvantage.

According to the present invention there is provided a stator assembly for an electrical rotating machine in which the laminations and the end shields are secured to form a rigid unit by means of a plurality of longitudinal welds.

In a preferred form there are a plurality of longitudinal welds arranged in zig-zag configuration around the stack of laminations extending between the two end shields.

In an alternative form, there is provided a first weld extending at least across the stack of laminations, and second and third welds extending at least part way around the respective circumferences of the end shields and respective outer laminations.

There may be a plurality of first welds around the stack of laminations, these being either in equispaced relation or random fashion.

In one preferred form, there are two first welds diametrically opposite one another, the second and third welds joining respective first and second ends in oppositely arranged semicircles.

The second and third welds together with the first weld may form an "H". There may be a plurality of "H" shaped welds around the stator.

The present invention will now be described in greater detail by way of example with reference to the accompanying drawings, wherein: Figure 1 is a diagrammatic side elevation view of a stator for a synchronous reluctance motor constructed in accordance with a preferred method of the present invention; Figure 2 is a diagrammatic side elevation view of a stator for a synchronous- reluctance motor constructed in accordance with an alternative method of the present invention; Figures 3A, 3B, 4A and 5 show various stages in the manufacture of a synchronous reluctance motor constructed in accordance with the method shown in Fig. 1 of the present invention.

Referring first to Fig. 1, the stator of the synchronous reluctance motor comprises a stack of laminations 2 and end shields 4 and 6. The stack of laminations is welded together by a number of inclined longitudinal welds 7 which extend from one shield 4 to the other end shield 6 at one inclination and back to the first end shield 4 at an opposite inclination to form a zig-zag arrangement around the circumference of the stator.

Referring to the alternative form shown in Fig. 2, the stack of laminations 2 is welded together by two first welds 8 arranged diametrically opposite each other. The end shield 4 is secured to one outermost lamination of the stack 2 by a second weld 10 whose ends join first ends of the first weld 8, the second weld 10 thus extending 180 around the circumference of the stator. Likewise, the end shield 6 is secured to the other outermost lamination of the stack 2 by a third wrld 12 whose end join second ends of the first welds 8, the third weld 12 thus extending 180 around the circumference of the stator, in the opposite direction from the second weld.

In both the above methods of construction, a multi-conductor cable 14 is provided for supplying current to the stator windings (not shown).

One preferred method of manufacturing the above described stator assembly for an electrical rotating machine will now be described in greater detail with reference to Figs. 3 to 5 and includes the following steps.

(a) The stack of laminations 2 is assembled using the appropriate number of laminations in accordance with the size of the machine to be made.

(b) Cuffed insulators 16 are inserted in the slots and when inserted temporarily secure the stack of laminations 2 as an assembly (Figs.

3A and 3B).

(c) The stator is wound with windings 18, coil connections are made to the cable 14, and wedges 20 inserted to hold the windings in place (Figs. 4A and 4B).

(d) The wound sub-assembly is then trickle impregnated with varnish.

(e) The rotor and shaft assembly 22 is fitted into the wound stator, using three equally spaced flexible strip shims 24 equivalent in thickness to the air-gap, to hold concentricity (Fig. 5).

(f) Bushes 26 are fitted onto each end of the rotor shaft and into end shields 4 and 6 aligning and passing the flexible shims 24 through grooves provided (Fig. 5).

(g) Welding fixture adaptor flanges 28 are fitted over each end shield 4 and 6 (Fig. 5).

(h) With the work rotating, the end shields 4 and 6 and the stack of laminations 2 are ultrasonically welded by zig-zag longitudinal welds around the periphery of the stator.

(i) On completion of the welding operation, the motor is removed from the fixture adaptor flanges 28.

(j) The shims 24 are then carefully extracted from the rotor and stator.

(k) Ball bearings are fitted up to shoulders at each end of the shaft, a circlip is added into the drive and shaft 6; a pre-load wave washer, cover disc and circlip are fitted into the leads end shield 4.

Ultrasonic welding is preferred for the following reasons: (1) The weld is carried out in a vacuum and the plasma beam is focussed into a very small spot, therefore little heat is generated.

(2) It is possible to complete the welding at a late stage in assembly without the risk of damaging the windings. The process can also be completed without causing corrosion of metal parts.

The weld pattern can follow any geometric form consistent with the object of achieving a permanent attachment of the laminations to each other as a stack and of the lamination stack to the end shields. Thus, whilst the above described zig-zag arrangement of the welds is preferred, other forms are possible.

Referring to Fig. 2, there need only be one first weld 8 whilst the second and third welds 10 and 12 need each only extend 90 around the circumference of the stator.

The first, second and third welds, in an alternative arrangement may form an "H". A plurality of H-shaped welds may extend around the circumference of the stator.

In each case the weld pattern is achieved by rotating the stator assembly whilst electromagnetically deflecting the plasma beam. It should be noted that there is a limit to the extent to which the beam can be deflected, with the result that above a certain lamination stack length, it is necessary to use twin welds each starting on the line of abutment of the lamination stack and respective end shields and overlapping each other during their axial traverse.

The above described processes are accurate and economical to carry out.

Also, the absence of bolts and nuts for securing the stator laminations and end shield means that the motor occupies less space and weighs less than a conventional motor of equal rating. This is particularly important in small motors.

Claims

1. A stator assembly for an electrical rotating machine in which the laminations and the end shields are secured to form a rigid unit by means of a plurality of longitudinal welds.

2. A stator assembly according to claim 1, wherein there are a plurality of longitudinal welds arranged in zig-zag configuration around the stack of laminations extending between the two end shields.

3. A stator assembly according to claim 1, wherein said plurality of longitudinal welds comprises a first weld extending at least across the stack of laminations, and second and third welds extending at least part way round the respective circumferences of the end shields and respective outer laminations.

4. A stator assembly according to claim 3, wherein there are a plurality of first welds arranged in equi-spaced relation around the stack of laminations.

5. A stator assembly according to claim 3, wherein there are a plurality of first welds arranged in random spacing around the stack of laminations.

6. A stator assembly according to claim 3, wherein there are two first welds arranged diametrically opposite one another, the second and third welds joining respective first and second ends in oppositely arranged semicircles.

7. A stator assembly according to claim 3, wherein the second and third welds form an "H" with the first weld.

8. A stator assembly according to claim 7, wherein a plurality of "H" spaced welds are arranged around the stator.

9. A stator assembly for an electrical rotating machine in which the laminations and end shields are secured to form a rigid unit by welding as shown in Fig. 1 or Fig. 2 of the accompanying drawings.

10. The method of manufacturing a stator assembling for an electrical rotating machine substantially as described with reference to Figs. 3 to 5 of the accompanying drawings.