Six Phase Synchronous Machine with AC and DC Stator Connections, Part II: Harmonic Studies and a Proposed Uninterruptible Power Supply Scheme

The relationships of the mutual leakage inductances with winding displacement angle and pitch for a number of practical six phase winding configurations are derived. The voltage harmonic distortion and torque pulsation of a six phase machine with AC-DC stator connections are characterized in terms of the operating load conditions, winding displacement angle, pitch, converter commutating reactance, and rotor impedance. It is shown that for most operating conditions a displacement angle of 300 appears to be optimum with respect to voltage harmonic distortion and torque pulsation. The effects of neglecting the mutual leakage coupling on the voltage harmonic distortion, torque pulsation and transient characteristics of the machine are examined. A novel application of the six phase machine in an uninterruptible power supply scheme is proposed. Results on the dynamic performance of the proposed UPS scheme to input voltage spikes and to a normal supply interruption are included.