Torque ripple optimization of skewed IPM motor for field weakening operation

Since last decade many novel interior permanent magnets motors' (IPM) have been developed and introduced in a mass production. Such design has many advantages comparing to well known surface motors' designs; especially it is very robust in terms of permanent magnet requirements: a simple block shape and lower quality issue. These factors play very important role particularly if the costs of neodymium magnet (NdFeB) are under high price fluctuation. Utilization of the IPM motor for sensitive application requires a skewing to minimize cogging and torque ripple. Unfortunately, a skewed IPM motor operates in a field weakening area causing increase of a torque ripple and a motor vibration. This phenomenon is caused by the load dependent reluctance within axial motor's length. This paper describes the presented problem and possible solution for an IPM motor used in automotive area.