IPM MACHINE WITH THERMALLY CONDUCTIVE COMPOUND
A synchronous electric machine includes a rotor having a substantially cylindrical core with axially extending slots, a plurality of permanent magnets configured as sets defining alternating poles in a circumferential direction, the permanent magnets being located in respective ones of the slots, and a thermally conductive material contiguous with the permanent magnets and the core for transferring heat of the permanent magnets, the material having a thermal conductivity of greater than 0.3 watts per (meter * Kelvin).
1 . A synchronous electric machine, comprising:
a rotor having a substantially cylindrical core with axially extending slots;
a plurality of permanent magnets being located in respective ones of the slots; and
a thermally conductive material contiguous with the permanent magnets and the core for transferring heat from the permanent magnets to the core, the material having a thermal conductivity of greater than 0.3 watts per (meter * Kelvin).
2 . The electric machine of claim 1 , wherein the thermally conductive material has a thermal conductivity of greater than 0.5 watts per (meter * Kelvin).
3 . The electric machine of claim 1 , wherein the thermally conductive material has a thermal conductivity of greater than 1.2 watts per (meter * Kelvin).
4 . The electric machine of claim 1 , wherein the thermally conductive material has a thermal conductivity of greater than 3.0 watts per (meter * Kelvin).
5 . The electric machine of claim 1 , wherein the thermally conductive material fully encapsulates the permanent magnets.
6 . The electric machine of claim 1 , wherein the permanent magnets are configured as sets defining alternating poles in a circumferential direction.
7 . A method of forming a rotor of an interior permanent magnet (IPM) electric machine, comprising:
positioning a plurality of permanent magnets in a corresponding plurality of axially-extending magnet slots of a rotor core;
encapsulating the plurality of permanent magnets with a material having a thermal conductivity of greater than 0.3 watts per (meter * Kelvin).
8 . The method of claim 7 , wherein the material has a thermal conductivity of greater than 0.5 watts per (meter * Kelvin).
9 . The method of claim 7 , wherein the material has a thermal conductivity of greater than 1.2 watts per (meter * Kelvin).
10 . The method of claim 7 , wherein the material has a thermal conductivity of greater than 3.0 watts per (meter * Kelvin).
11 . The method of claim 7 , wherein the encapsulating comprises injecting a thermally conductive powder into the plurality of magnet slots.
12 . The method of claim 11 , further comprising dynamically compacting the conductive powder within the magnet slots.
13 . The method of claim 12 , wherein the dynamic compacting comprises vibrating the rotor.
14 . The method of claim 7 , wherein the permanent magnets are encapsulated in thermally conductive resin before insertion into the magnet slots.
15 . The method of claim 7 , further comprising magnetizing the permanent magnets after the encapsulating.
16 . The method of claim 11 , wherein the powder comprises thermally conductive polymers.
17 . The method of claim 16 , wherein the powder comprise alumina.
18 . The method of claim 16 , wherein the powder comprise boron nitride.
19 . The method of claim 11 , further comprising melting the powder and then adding a binder to the thermally conductive material.
20 . The method of claim 7 , further comprising magnetizing the permanent magnets before the encapsulating.
21 . The method of claim 7 , wherein the encapsulating is performed both before and after the positioning of the permanent magnets.
22 . The method of claim 7 , further comprising floating the permanent magnets prior to completing the encapsulating, whereby the permanent magnets are finally bonded into a static position based on magnetic alignment.