Modelling and identification for reduction of overvoltage transients

Abstract

The main problems that appear when using a long cable connection between a Variable Frequency Drive (VFD) and the AC motor are over-voltages and bearing currents. The last one concerns especially EMC, while the over-voltage transients can be fatal to the motor. This paper firstly investigates the "converter -cable -motor" system behaviour concerning overvoltages. Then it proposes an online identification of the cable parameters. This result could be used in order to reduce over-voltages. We introduce here an algorithm that decreases the amplitude of the adverse over-voltage effect. The algorithm is based on the modification of the applied PWM pattern.