Analysis of higher harmonics loss in nine-phase salient pole synchronous machine

In concentrated winding multi-phase permanent magnet machines, harmonic currents are intentionally injected to produce additional torque. However, harmonics result additional power losses, core temperature rise and reduction in efficiency. In this paper, analysis on the electrical power losses due to the harmonics in nine-phase permanent magnet synchronous motor is done. Analytical loss model and modified nine-phase machine, accounting for the power losses are derived. The analytical model is to generate the flux distribution in different regions of the machine and determine the losses as the result of the non-sinusoidal flux distribution. The modified model for nine-phase machine is presented to show an appropriate operating points which minimizes the total electrical loss (copper plus core loss). Comparison of power loss and efficiency in nine-phase machine with that of equivalent three phase machines is also explored.