Slot wedges for electrical machines
A wound core assembly for an electrical machine comprising a stack of laminations defining a core having a plurality of poles, the wound core assembly further comprising at least one slot wedge, wherein the slot wedge comprises a first portion arranged between adjacent poles and at least one second portion protruding from the first portion and abutting an end face of the core in the region of at least one of the poles. The at least one second portion may apply axial pressure to the end face to reduce the tendency of the laminations to splay axially outwards.
1. A wound core assembly for an electrical machine, the wound core assembly comprising a stack of laminations secured together to define a core having a plurality of poles, the poles each having a first end at which they are connected to the remainder of the core and having an opposed second end, the wound core assembly further including a plurality of slot wedges made from an insulating material, wherein each one of the plurality of slot wedges includes a first portion disposed with an interference fit between adjacent poles adjacent their second ends to define a space for a winding between the slot wedge and the core and includes at least one second portion protruding from the first portion and applying pressure to an end face of the core in the region of one of the poles that is adjacent thereto, wherein the pressure provided by the plurality of slot wedges substantially prevents splaying of a lamination at each end face and holds the lamination in its correct position against the core.
2. A wound core assembly according to claim 1 , wherein the slot wedge has one single second portion.
3. A wound core assembly according to claim 1 , wherein the slot wedge is substantially “L” shaped.
4. A wound core assembly according to claim 1 , wherein the slot wedge is arranged to engage the end face only in the region of one single pole.
5. A wound core assembly according to claim 1 , wherein the slot wedge has at least two of the second portions.
6. A wound core assembly according to claim 5 , wherein the at least two second portions extend from opposite sides of the slot wedge.
7. A wound core assembly according to claim 1 , wherein the slot wedge is substantially “T” shaped.
8. A wound core assembly according to claim 7 , wherein the slot wedge is symmetrical about a centre line.
9. A wound core assembly according to claim 5 , wherein the second portions engage the end face in the region of two of the poles.
10. A wound core assembly according to claim 1 , wherein the slot wedge is a unitary piece of material.
11. A wound core assembly according to claim 1 , wherein the slot wedge is constructed from more than one piece of material.
12. A wound core assembly according to claim 1 , wherein the slot wedge comprises a glass-reinforced epoxy resin.
13. A wound core assembly according to claim 1 , in which the junction between the first portion and the second portion defines a recess.
14. A wound core assembly according to claim 1 , further comprising a plurality of windings.
15. A method for assembling a wound core assembly for an electrical machine, the assembly including a stack of laminations defining a core having a plurality of poles, a space between adjacent poles defining a slot, wherein the method comprises securing the laminations together to form the stack and then inserting a plurality of slot wedges into the slots, each one of the plurality of slot wedges made from an insulating material and having at least one protruding portion into the slot such that the slot wedge is secured with an interference fit between adjacent poles and the at least one protruding portion applies pressure to an end face of the core to support the end face, wherein the pressure provided by the plurality of slot wedges substantially prevents splaying of a lamination at each end face and holds the lamination in its correct position against the core.
16. A method as claimed in claim 15 including disposing a portion of a winding for the wound core assembly in the slot prior to inserting the slot wedge.
17. A wound core assembly according to claim 1 , wherein the stack of laminations is welded or cleated together.
18. A method as claimed in claim 15 , wherein the securing the laminations together includes welding or cleating the laminations together.
19. A wound core assembly according to claim 1 , wherein there is at least one of the slot wedges disposed between each pair of poles of the core.
20. A method as claimed in claim 15 , wherein the inserting comprises inserting at least one of the slot wedges having at least one protruding portion into the slot between each pair of poles of the core such that each of the slot wedges is secured with an interference fit between adjacent poles and the at least one protruding portion applies pressure to an end face of the core to support the end face.