Permanent magnet machine with different pole arc angles
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. Asymmetry is achieved by placing adjacent permanent magnets or magnet sets on the rotor periphery with different rotor magnetic pole arc angles.
1. 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 patterns for the electromagnetic stator windings to create rotor torque,
the magnets of one pair for one section defining an arc angle therebetween that differs from an arc angle defined by the magnets of an adjacent rotor section whereby harmonic components of rotor torque are manipulated to obtain smooth torque production, and
the length of magnets in one section being different than the length of magnets of another section whereby motor torque fluctuations are modified.
2. The permanent magnet machine set forth in claim 1 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.
3. The permanent magnet machine set forth in claim 1 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.
4. The permanent magnet machine set forth in claim 1 wherein the magnets of each pair define an interpolar 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 interpolar axis of one rotor section being in axial alignment with the magnetic interpolar axis of an adjacent rotor section having a different magnet arrangement.