Output voltage wave form is step type sine wave by multi-level PWM control.

Also, output current wave form is close to sine wave. Therefore, the additional heat loss caused by

the harmonic currents are negligible.

Switching surge voltage which causes a damage to the insulation of the motor is smaller compared

with that of two level PWM inverter, owing to unique control of the switching of each IGBT.

Therefore, no motor kW derating is required and retrofitting application is possible.

(In case of the retrofitting application, it should be checked whether the motor and the driven