Filtered PWM-inverter drive for high-speed solid-rotor induction motors

Inverter output harmonics create a great amount of losses especially in solid-rotor induction motors. The output sine filter for the PWM-inverter is introduced to smooth the inverter output waveforms. Therefore inverter disadvantages will be avoided and the efficiency of the solid-rotor induction motor will increase remarkably. The filter is designed so that it also compensates the magnetising current of the motor, thus poor power factor of the solid rotor induction motors does not affect inverter sizing. The EMC matters, voltage stress in stator windings and bearing currents are also examined. This paper focuses on effects of the filter to the characteristics of the solid-rotor induction motors. Measurements of 12 kW, 13500 rpm prototype are given