High-Frequency Leakage Currents in Medium Power Adjustable Speed Drives supplied from IT Mains

Low voltage frequency converters (VFCs) for ac drives supplied from isolation terra (IT) mains can produce voltage spikes in the supplying mains. The spikes are minimalized by earthed electromagnetic compatibility (EMC) filter which is built in intermediate circuit of VFC. In adjustable frequency drive (AFD) of medium and high power (up to 1MVV) the voltage spikes cause damages of voltage frequency converter. Description, conclusion, experimental and simulation results of AFD with earthed and non earthed EMC filter located in the intermediate circuit are presented in this paper.