IMPACT OF SLOT HARMONICS ON LOSSES OF HIGH-SPEED PERMANENT MAGNET MACHINES WITH A MAGNET RETAINING RING

This paper presents an analytical method for determining the harmonic content in the flux pattern of permanent magnet synchronous machines due to the slotting of the stator. The analysis based on a rotor construction with magnets radially magnetized and a retaining ring to support them against the centrifugal forces. Expressions for the eddy current losses in the magnets and their retaining ring are derived in terms of the machine dimensions and the physical properties of magnets and ring. The accuracy of the method is examined by comparison with numerical flux calculations using finite element method. The impact of some physical quantities like machine speed and magnet conductivity on the slot harmonics losses is examined aiming to exhibit the role of the magnet retaining ring in contributing to these losses