Comparison of radial vibration forces in 10-pole/12-slot fractional slot surface-mounted and interior PM brushless AC machines

This paper compares the radial vibration forces in 10-pole/12-slot fractional-slot SPM and IPM machines which are designed to produce the same output torque, and employ an identical stator but different SPM, V-shape and arc-shape IPM rotor topologies. The airgap field and radial vibration force density distribution as a function of angular position and corresponding space harmonics (vibration modes) are analysed using the finite element method together with frozen permeability technique. It is shown that not only the lowest harmonic of radial force in IPM machine is much higher, but also the (2p)^th harmonic of radial force in IPM machine is also higher than that in SPM machine.