Rotor assembly
The disclosure relates to a stator assembly for an electric machine. Example embodiments disclosed include a rotor assembly for an electric machine, the rotor assembly comprising: a rotor core; a plurality of magnets arranged around the rotor core; and a cylindrical rotor sleeve surrounding the plurality of magnets, wherein the rotor sleeve comprises a laminated composite material having an array of ferromagnetic pins extending through a thickness of the rotor sleeve.
1 . A rotor assembly for an electric machine, the rotor assembly comprising:
a rotor core;
a plurality of magnets arranged around the rotor core; and
a cylindrical rotor sleeve surrounding the plurality of magnets,
wherein the rotor sleeve comprises a laminated composite material having an array of ferromagnetic pins extending through a thickness of the rotor sleeve.
2 . The rotor assembly of claim 1 , wherein the array of ferromagnetic pins extends around the rotor sleeve with a circumferential areal density of between around 0.5% and 2%.
3 . The rotor assembly of claim 1 , wherein the ferromagnetic pins are composed of a soft magnetic material.
4 . The rotor assembly of claim 1 , wherein the ferromagnetic pins have a diameter of between around 0.25 mm and around 0.5 mm.
5 . The rotor assembly of claim 1 , wherein the ferromagnetic pins are aligned radially through the thickness of the rotor sleeve.
6 . The rotor assembly of claim 1 , wherein the ferromagnetic pins are uniformly distributed around the rotor sleeve.
7 . The rotor assembly of claim 1 , wherein the rotor sleeve comprises a first inner layer and a second outer layer, the ferromagnetic pins extending through a thickness of the first inner layer.
8 . The rotor assembly of claim 1 , wherein the laminated composite material comprises a first plurality of layers of a first composite material interleaved with a second plurality of layers of a second composite material.
9 . The rotor assembly of claim 8 , wherein the first composite material is a GFRP and the second material is a CFRP.
10 . The rotor assembly of claim 8 , wherein the first composite material comprises fibres aligned at between around 30° and 60° to a longitudinal axis of the rotor sleeve.
11 . The rotor assembly of claim 8 , wherein the second composite material comprises fibres aligned at around 90° to a longitudinal axis of the rotor sleeve.
12 . An electric machine comprising:
a stator assembly; and
a rotor assembly according to claim 1 within the stator assembly.
13 . A method of manufacturing a rotor sleeve for an electric machine, the method comprising:
winding a resin-impregnated fibrous material around a cylindrical mandrel to form a laminated composite material rotor sleeve; and
inserting a plurality of ferromagnetic pins through a thickness of the rotor sleeve to provide an array of ferromagnetic pins around the rotor sleeve.
14 . The method of claim 13 , wherein the array of ferromagnetic pins extends around the rotor sleeve with the pins covering a circumferential areal density of between around 0.5% and 2%.
15 . The method of claim 13 , wherein the ferromagnetic pins are composed of a soft magnetic material.
16 . The method of claim 13 , wherein the ferromagnetic pins have a diameter of between around 0.25 mm and around 0.5 mm.
17 . The method of claim 13 , wherein the ferromagnetic pins are aligned radially through the thickness of the rotor sleeve.
18 . The method of claim 13 , wherein the ferromagnetic pins are uniformly distributed around the rotor sleeve.
19 . The method of claim 13 , comprising winding a further resin-impregnated fibrous material around the rotor sleeve following insertion of the plurality of ferromagnetic pins.
20 . A method of manufacturing a rotor assembly for an electric machine, comprising:
manufacturing a rotor sleeve according to the method of claim 13 ; and
fitting the rotor sleeve around a plurality of magnets arranged around a rotor core.