Permanent magnet module for an electrical machine
A permanent magnet module for a rotor of a permanent magnet electrical machine is presented. The permanent magnet module comprises: a stack of ferromagnetic steel sheets ( 104 ) having a groove in the direction perpendicular to the ferromagnetic steel sheets, and a permanent magnet ( 105 ) located in the groove and arranged to produce magnetic flux that penetrates a surface ( 106 ) of the stack of ferromagnetic steel sheets. The surface has a shape suitable for forming a desired magnetic flux density distribution into an air-gap of the permanent magnet electrical machine. The permanent magnet module further comprises a base-plate ( 102 ) made of solid ferromagnetic steel. The base plate is located at an opening ( 116 ) of the groove and constitutes together with the groove an aperture in which the permanent magnet is located.
1. A permanent magnet module ( 101 , 201 , 301 ) for a rotor of a permanent magnet electrical machine, the permanent magnet module extending over at most 180 degrees in a tangential direction (φ) of the rotor and comprising:
a stack of ferromagnetic steel sheets ( 104 , 204 , 304 ) comprising at least one groove in a direction perpendicular to the ferromagnetic steel sheets,
at least one permanent magnet ( 105 , 205 , 305 a - 305 h ) located in the at least one groove and arranged to produce magnetic flux that penetrates a surface ( 106 , 206 ) of the stack of ferromagnetic steel sheets, the surface of the stack of ferromagnetic steel sheets having a shape suitable for forming a pre-determined magnetic flux density distribution into an air-gap of the permanent magnet electrical machine, and
a supporting structure ( 114 , 214 , 215 ) arranged to mechanically support the stack of ferromagnetic steel sheets,
characterized in that the permanent magnet module further comprises at least one base-plate ( 102 , 202 , 302 ) made of solid ferromagnetic steel, each base-plate being located at an opening ( 116 , 216 , 316 ) of one of the at least one groove and constituting together with the at least one groove an aperture in which the at least one permanent magnet is located.
2. A permanent magnet module according to claim 1 , wherein the permanent magnet module comprises at least one aperture ( 217 , 317 ) arranged to allow flow of cooling fluid through the stack of ferromagnetic steel sheets.
3. A permanent magnet module according to claim 1 , wherein the opening ( 216 ) of the groove is arranged to constitute a T-shaped groove and the base-plate ( 202 ) is arranged to constitute a T-shaped wedge for fastening the permanent magnet module to a central part ( 210 ) of the rotor.
4. A permanent magnet module according to claim 1 , wherein the opening ( 316 ) of the groove is arranged to constitute a dovetail-shaped groove and the base-plate ( 302 ) is arranged to constitute a dovetail-shaped wedge for fastening the permanent magnet module to a central part of the rotor.
5. A permanent magnet module according to claim 1 , wherein permanent magnet module is provided with a hermetic coating.
6. A permanent magnet module according to claim 5 , wherein the hermetic coating is made of resin.
7. A permanent magnet module according to claim 1 , wherein permanent magnet module comprises an end-plate ( 209 , 213 , 309 , 313 ) at both ends of the stack of ferromagnetic steel sheets, the end-plates, the at least one base-plate, and the at least one groove forming at least one cavity for the at least one permanent magnet.
8. A permanent magnet module according to claim 7 , wherein the end-plates are made of nonmagnetic material.
9. A permanent magnet module according to claim 1 , wherein the permanent magnet module comprises a damper winding ( 218 , 219 , 220 ).
10. A permanent magnet module according to claim 1 , wherein the permanent magnet comprises at least two pieces ( 305 a , 305 b ) of permanent magnet material located successively in the tangential direction (φ) of the rotor.
11. A permanent magnet module according to claim 1 , wherein the permanent magnet comprises at least two pieces ( 305 a , 305 c ) of permanent magnet material located successively in the direction perpendicular to the ferromagnetic steel sheets.
12. A rotor ( 429 ) of a permanent magnet electrical machine, the rotor comprising a central part ( 432 ) having a shaft ( 433 ), characterized in that the rotor comprises at least two permanent magnet modules ( 401 , 401 a , 401 b , 401 c ) according to claim 1 on a surface of the central part and located successively in the tangential direction (φ) of the rotor.
13. A permanent magnet electrical machine having a rotor ( 429 ) that comprises a central part ( 432 ) having a shaft ( 433 ), characterized in that the rotor comprises at least two permanent magnet modules ( 401 , 401 a , 401 b , 401 c ) according to claim 1 on a surface of the central part and located successively in the tangential direction (φ) of the rotor.
14. A method for assembling a rotor of a permanent magnet electrical machine, characterized in that the method comprises installing ( 501 ) a permanent magnet module according to claim 1 onto a surface of a central part of the rotor.
15. A method for assembling a permanent magnet electrical machine, the method comprising installing ( 601 ) a rotor into a stator bore of the permanent magnet electrical machine, characterized in that the rotor comprises at least two permanent magnet modules according to claim 1 on a surface of a central part of the rotor and located successively in the tangential direction of the rotor.