Effects of modified modulation strategies on bearing currents and operational characteristics of AC induction machines

Newest investigations have shown that bearing currents can be lowered by using modified pulse pattern generation methods. One suggestion for such a solution is the principle of sequentially positioned pulses. Hereby, a modified space vector modulation is used, in order to reduce both the amplitude of and the number of potential alterations in the common mode voltage. This voltage is the reason for EDM and dv/dt currents which are mostly responsible for severe bearing damages in modem inverter fed drive applications. The paper will show the fundamental basics concerning this principle and its characteristic influences on the operational behaviour of an inverter fed AC induction machine.