Cooling of high-power permanent magnet machine rotor
A rotor of an electric machine includes a rotor core, a plurality of permanent magnets located at the rotor core, and a rotor sleeve enclosing the rotor core and the plurality of permanent magnets. One or more sleeve cooling channels are positioned between a radially outer surface of the rotor core and a radially inner surface of the rotor sleeve and extend axially along a length of the rotor. One or more radial cooling channels extend radially outwardly from an interior of the rotor core to the one or more sleeve cooling channels. The one or more radial cooling channels are configured to convey a flow of cooling fluid from the interior of the rotor core to the one or more sleeve cooling channels.
1 . An electric machine, comprising:
a stator including a stator winding; and
a rotor configured to rotate about a machine central axis and electromagnetically interactive with the stator across an air gap between the rotor and the stator, the rotor including:
a rotor core;
a plurality of permanent magnets disposed at the rotor core;
a rotor sleeve enclosing the rotor core and the plurality of permanent magnets;
one or more sleeve cooling channels disposed between a radially outer surface of the rotor core and a radially inner surface of the rotor sleeve and extending axially along a length of the rotor;
a first mid-stack plate disposed in the rotor core including one or more first radial cooling channels formed in the first mid-stack plate; and
a second mid-stack plate disposed in the rotor core including one or more second radial cooling channels formed in the second mid-stack plate;
wherein the one or more first radial cooling channels and the one or more second radial cooling channels extend radially outwardly from an interior of the rotor core to the one or more sleeve cooling channels, the one or more first radial cooling channels and the one or more second radial cooling channels configured to convey a flow of cooling fluid from the interior of the rotor core to the one or more sleeve cooling channels.
2 . The electric machine of claim 1 , wherein the one or more first radial cooling channels and the one or more second radial cooling channels are positioned in an axial interior of the rotor core between a first axial end and a second axial end of the rotor core.
3 . The electric machine of claim 2 , wherein one of the one or more first radial cooling channels or the one or more second radial cooling channels are located at an axial midpoint of the rotor core.
4 . The electric machine of claim 1 , wherein the flow of cooling fluid is directed into the one or more first radial cooling channels and the one or more second radial cooling channels from a hollow interior of a rotor shaft.
5 . The electric machine of claim 1 , wherein the one or more first radial cooling channels is a plurality of first radial cooling channels circumferentially spaced apart in the rotor core.
6 . The electric machine of claim 1 , wherein the one or more first radial cooling channels and the one or more second radial cooling channels is a plurality of radial cooling channels at two different axial locations of the rotor.
7 . The electric machine of claim 1 , further comprising one or more sleeve cooling channel outlets at one or more axial ends of the one or more sleeve cooling channels, the one or more sleeve cooling channel outlets configured to direct the flow of cooling fluid toward an end turn of the stator winding.
8 . A rotor of an electric machine, comprising:
a rotor core;
a plurality of permanent magnets disposed at the rotor core;
a rotor sleeve enclosing the rotor core and the plurality of permanent magnets;
one or more sleeve cooling channels disposed between a radially outer surface of the rotor core and a radially inner surface of the rotor sleeve and extending axially along a length of the rotor;
one or more radial cooling channels extending radially outwardly from an interior of the rotor core to the one or more sleeve cooling channels, the one or more radial cooling channels configured to convey a flow of cooling fluid from the interior of the rotor core to the one or more sleeve cooling channels; and
one or more sleeve cooling channel outlets of the one or more sleeve cooling channels defined at an axial end of the rotor assembly, so that the flow of cooling fluid exits the one or more sleeve cooling channel outlet in an axial direction;
wherein the one or more radial cooling channels is a plurality of radial cooling channels at two different axial locations of the rotor.
9 . The rotor of claim 8 , wherein the one or more radial cooling channels are positioned in an axial interior of the rotor core between a first axial end and a second axial end of the rotor core.
10 . The rotor of claim 9 , wherein the one or more radial cooling channels are located at an axial midpoint of the rotor core.
11 . The rotor of claim 8 , wherein the flow of cooling fluid is directed into the one or more radial cooling channels from a hollow interior of a rotor shaft.
12 . The rotor of claim 8 , further comprising a mid-stack plate disposed in the rotor core, the one or more radial cooling channels formed in the mid-stack plate.
13 . The rotor of claim 8 , wherein the one or more radial cooling channels is a plurality of radial cooling channels circumferentially spaced apart in the rotor core.
14 . The rotor of claim 8 , wherein the one or more sleeve cooling channel outlets are configured to direct the flow of cooling fluid toward an end turn of a stator winding of the electric machine.
15 . A method of cooling a rotor of a permanent magnet electric machine, comprising:
directing a flow of cooling fluid into an interior of a rotor core of the rotor;
wherein one or more first radial cooling channels are formed in a first mid-stack plate disposed in the rotor core; and
wherein one or more second radial cooling channels are formed in a second mid-stack plate disposed in the rotor core;
urging the flow of cooling fluid radially outwardly through the one or more first radial cooling channels and radially outwardly through the one or more second radial cooling channels defined in the rotor core; and
directing the flow of cooling fluid from the one or more first radial cooling channels and from the one or more second radial cooling channels along one or more sleeve cooling channels extending in an axial direction between the rotor core and a rotor sleeve surrounding the rotor core.
16 . The method of claim 15 , wherein the one or more first radial cooling channels and the one or more second radial cooling channels are positioned in an axial interior of the rotor core between a first axial end and a second axial end of the rotor core.
17 . The method of claim 15 , wherein the one or more first radial cooling channels are axially spaced apart from the one or more second radial cooling channels in the rotor core.
18 . The electric machine of claim 1 , wherein the one or more first radial cooling channels are circumferentially offset from the one or more second radial cooling channels.