Space Vector Based Investigation of Overmodulation Region of Inverter Fed Multiphase AC Drives

Space vector investigation of multi-phase inverters in overmodulation region is presented in the paper to study ac motor harmonic losses. It is shown that, in full overmodulation region the optimization of additional switching angles of inverter does not ensure the acceptable decrease of motor harmonic losses. Therefore the motor voltage region above 80-87% of the inverter maximum possible value is virtually restricted at least for a steady state operation. At the same time, the space vector investigation of multi-phase system - in comparison to other methods of investigation and opposite to 3-phase system is more difficult and seems less effective.