Hidden reflection phenomena on inverter-fed induction motors

When supplying an induction motor by a PWM-inverter through long cables, reflections occur. For some inverters other reflection phenomena than the usual overvoltages appear at the motor side, namely steps smaller than 0.5 p.u. of the busvoltage, also called stair stepping. The stair stepping reflection phenomenon occurs at the commutation from IGBT to diode. Stair stepping depends on the magnitude of the current, the cable impedance and on the dead time of the IGBT gate-signal. The reflection phenomenon increases the turn on time of the diode.