Torque Ripple Minimization of PM-assisted Synchronous Reluctance Machines via Asymmetric Rotor Poles

Torque ripple minimization is one of the design challenges of PM-assisted Synchronous Reluctance (PM-SyR) machines. Very often, time-consuming FEA based optimization is the preferred design strategy. Also very often, the ultimate remedy to torque ripple is to skew or step-skew the rotor of the machine, at the cost of average torque reduction. Asymmetric-pole rotors demonstrated good torque oscillation smoothing capability for Synchronous Reluctance machines; previous work showed that the Flux Barriers Shift (FBS) technique can be applied off-line to a regular design, same as skewing, with no average torque reduction. This paper extends the validity of the FBS technique to PM-SyR machines. The PM-SyR machine design flowchart is reviewed and augmented with FBS. Torque waveforms obtained with FBS and skewing are compared using FEA. Finally, the FBS design is validated against a regular design with dedicated experimental tests.