Motor

A permanent magnet rotor assembly having a plurality of magnetic poles, comprising the following components:

• a plurality of magnetic pole pieces arranged in circular array, the magnetic pole pieces having circumferential gaps between them;
• an array of circumferentially magnetised magnets placed in the circumferential gaps wherein the circumferentially adjacent magnets are magnetised in opposite directions to each other;
• magnetic end-plates having an axial position with respect to the circular array of magnetic pole pieces so that an axial gap exists between each magnetic end-plate and the magnetic pole pieces;
• circular arrays of magnets providing flux in an axial direction placed in the axial gaps wherein circumferentially adjacent magnets in each array are magnetised in opposite directions to each other;
• a shaft used to transmit torque between the rotor and a prime-mover in generation mode and between the rotor and a load in motor mode;
• and
• a flux barrier region having high magnetic reluctance between the (i) shaft and (ii) the magnetic pole pieces and the arrays of magnets
• wherein one of the end-plates and the corresponding array of magnets providing flux in an axial direction are located at each end of the rotor assembly;
• wherein the magnetic end-plates connect the shaft to the rest of the rotor assembly.