Analysis and modelling of common-mode oscillations of electrical drive systems with active front end and long motor cables

This paper presents an analysis of common-mode oscillations in electrical drive systems. The analysed oscillations occur particularly in electrical drive systems with active front end, common DC-link and long shielded motor cables. Because of resonant frequencies at 10 to 40 kHz low damping occurs. In the concerned frequency range switching operations generate a significant excitation. As the focus of this paper the common mode system of an electrical drive system is analysed and modelled. The damping behaviour of the choke and the switching of active front end and inverters have to be analysed very carefully. Simulations and measurements show apparent voltage stressing of motors, common mode losses and currents that disturb the drive system.