Unbalanced operation of current regulated sine-wave interior permanent magnet machines

The behavior of rotor eccentricities in current regulated interior permanent magnet (IPM) machines is investigated. The study focuses on two typical topologies of significant industrial relevance, i.e. machines with distributed windings with two slots per pole and phase and motors with concentrated coils and with three slots per pole pair, respectively. The effect of stator winding parallel paths is examined for both cases. Coil and terminal electrical quantities, radial forces, and torque ripple were simulated using FEA. Unbalanced operation, where the currents are not equal in parallel phase connections due to the eccentricity, is also investigated. Experimental measurements of electrical quantities and forces with static eccentricity are carried out with two special test fixtures. The experimental measurements validated the simulation results.