Permanent Magnet Machine with Offset Pole Spacing

Abstract

An internal permanent magnet machine has multiple rotor sections, each section having multiple rotor laminations. Permanent magnets are placed asymmetrically in lamination openings to attenuate oscillations in torque caused by harmonic components of magnetic flux.

1 . A permanent magnet electric machine comprising:
 a stator with electromagnetic windings for stator poles;   a rotor located coaxially with the stator and having an air gap therebetween; and   a plurality of permanent magnets positioned on the rotor periphery so that magnetic poles of adjacent magnets are asymmetrical, whereby harmonic components of air gap magnetic flux are attenuated to reduce undesirable oscillation of rotor torque.   
   
   
       2 . A permanent magnet machine comprising a stator with electromagnetic windings for stator poles and a rotor located on a rotor axis that is common to an axis for the stator with an air gap between the stator and the rotor;
 the rotor having a plurality of permanent magnets on its periphery; and   magnetic poles for the magnets being characterized by magnetic flux flow patterns that interact with flux flow paths for the electromagnetic stator windings to create rotor torque;   the magnetic poles being asymmetrically positioned on the rotor periphery whereby harmonic components of air gap flux are attenuated to reduce undesirable oscillation of rotor torque.   
   
   
       3 . The permanent magnet machine set forth in  claim 2  wherein the magnets are positioned on the rotor to effect radial skewing, the poles of at least one pair of adjacent magnets being spaced in closer proximity than poles of other magnet pairs on the rotor periphery whereby asymmetry is achieved. 
   
   
       4 . The permanent magnet machine set forth in  claim 3  wherein pairs of magnets define rotor poles with a rotor pole axis that are non-uniformly spaced about the rotor periphery with respect to rotor pole axes defined by other adjacent pairs of magnets. 
   
   
       5 . The permanent magnet machine set forth in  claim 3  wherein the rotor pole axes are uniformly spaced about the rotor periphery. 
   
   
       6 . A permanent magnet machine comprising a stator with electromagnetic windings for stator poles and a rotor located on a rotor axis that is common to an axis for the stator with an air gap between the stator and the rotor;
 the rotor having a plurality of pairs of permanent magnets on its periphery, the magnets of each pair being located in a “V” shape configuration defining an angle therebetween;   the rotor comprising laminations arranged in multiple sections in stacked axial relationship;   magnetic poles for the magnet pairs being characterized by flux flow patterns that interact with flux flow paths for the electromagnetic stator windings to create rotor torque;   the magnets of one pair for one section defining an angle therebetween that differs from an angle defined by the magnets of an adjacent rotor section whereby harmonic components of rotor torque are manipulated to obtain smooth torque production.   
   
   
       7 . The permanent magnet machine set forth in  claim 6  wherein the magnets have pre-calculated lengths and widths, the width of the magnets in one section being different than a corresponding width of magnets of another section whereby rotor torque fluctuations are modified. 
   
   
       8 . The permanent magnet machine set forth in  claim 6  wherein the shape of the magnets in one section are different than the shape of the magnets in another section whereby motor torque fluctuations are modified. 
   
   
       9 . The permanent magnetic machine set forth in  claim 6  wherein the length of magnets in one section are different than the length of magnets of another section whereby motor torque fluctuations are modified. 
   
   
       10 . The permanent magnet machine set forth in  claim 6  wherein the magnets of each pair define a magnetic axis;
 the rotor having at least two rotor sections arranged in axially-stacked relationship, each rotor section having a plurality of laminations in stacked assembled relationship;   the magnetic pole axis of one rotor section being in axial alignment with the magnetic pole axis of an adjacent rotor section having a different magnet arrangement.   
   
   
       11 . A permanent magnet machine comprising a stator with electromagnetic windings for stator poles and a rotor located on a rotor axis that is common to an axis for the stator with an air gap between the stator and the rotor;
 the rotor having a plurality of pairs of permanent magnets on its periphery, the magnets of each pair being located in a “V” shape configuration defining an angle therebetween;   the rotor comprising laminations arranged in multiple sections in stacked axial relationship;   magnetic poles for the magnet pairs being characterized by flux flow patterns that interact with flux flow paths for the electromagnetic stator windings to create rotor torque;   the magnets of one pair for one section defining an angle therebetween that differs from an angle defined by another pair of magnets of the same rotor section whereby harmonic components of rotor torque are manipulated to obtain smooth torque production.   
   
   
       12 . The permanent magnet machine sets forth in  claim 11  wherein the magnets have pre-calculated lengths and widths, the width of the magnets in one section being different than a corresponding width of magnets of another section whereby rotor torque fluctuations are modified. 
   
   
       13 . The permanent magnet machine set forth in  claim 11  wherein the length of magnets in one section are different than the length of magnets of another section whereby rotor torque fluctuations are modified. 
   
   
       14 . The permanent magnet machine set forth in  claim 11  wherein the magnets of each pair define a magnetic axis;
 the rotor having at least two rotor sections arranged in axially-stacked relationship, each rotor section having a plurality of laminations in stacked assembled relationship;   the magnetic axis of one rotor section being in axial alignment with the magnetic axis of an adjacent rotor section having a different magnet arrangement.   
   
   
       15 . A permanent magnet machine comprising a stator with electromagnetic windings for stator poles and a rotor located on a rotor axis that is common to an axis for the stator with an air gap between the stator and the rotor;
 the rotor comprising a plurality of axially-stacked sections, each section comprising a plurality of stacked laminations on a rotor shaft with a key and slot driving connection therebetween;   each section having a plurality of magnets located on its periphery, the magnets creating a magnetic flux pattern that interacts with a magnetic flux pattern created by the magnetic windings of the stator poles to develop rotor torque;   the laminations in one section having asymmetrically placed first magnet openings for receiving rotor magnets;   the laminations of a second section having asymmetrically placed second magnet openings for receiving rotor magnets;   the magnet openings for the laminations of the first section having a common geometry with respect to the magnet openings for the laminations of the second section to permit manufacture with a common machine tool;   the laminations for the second section being flipped about a radial axis relative to the laminations for the first section following assembly of the rotor, the rotor openings for the laminations of the second section being angularly displaced relative to the rotor openings for the laminations of the first section, whereby rotor torque fluctuations are attenuated.   
   
   
       16 . The permanent magnet machine set forth in  claim 15  wherein the rotor comprises more than two rotor sections, the laminations for the second section being flipped about a first radial axis relative to the laminations of the first rotor section; and
 the laminations for a third rotor section being flipped about a second radial axis relative to the laminations of the first rotor section, whereby rotor torque fluctuations are attenuated.   
   
   
       17 . The permanent magnet machine set forth in  claim 16  whereby the first and second radial axes are displaced to an angle Delta. 
   
   
       18 . The permanent magnet machine set forth in  claim 15  whereby the sections are displaced angularly, one with respect to the other, about a geometric rotary axis of the rotor during assembly of the rotor sections. 
   
   
       19 . The permanent magnet machine set forth in  claim 15  wherein the laminations of one section have driving key and slot features at locations spaced approximately 180° apart about a geometric rotary axis of the rotor. 
   
   
       20 . The permanent magnet machine as set forth in  claim 16  wherein the laminations of the first section has first driving key and slot features at locations spaced approximately 180° apart about a geometric rotary axis of the rotor;
 the laminations of the second section having second driving key and slot features at locations spaced approximately 180° apart about the geometric rotary axis of the rotor;   the first driving key and slot features being relatively displaced approximately 90° from the second driving key and slot features.   
   
   
       21 . The permanent magnet machine set forth in  claim 20  wherein the permanent magnet machine has third and fourth lamination sections with driving key and slot features relatively displaced to an angle Delta from the second driving key and slot features of the laminations of the first and second sections. 
   
   
       22 . The permanent magnet machine set forth in  claim 21  wherein the laminations of the third and fourth sections are flipped about radial axes extending through the first and second key and slot features. 
   
   
       23 . The permanent magnet machine set forth in  claim 20  wherein the key and slot features are configured to provide axial alignment of the lamination sections in axially stacked relationship. 
   
   
       24 . The permanent magnet machine set forth in  claim 21  wherein the key and slot features are configured to provide axial alignment of the lamination sections in axially stacked relationship. 
   
   
       25 . The permanent magnet machine set forth in  claim 22  wherein the key and slot features are configured to provide axial alignment of the lamination sections in axially stacked relationship.