Improvement of power converter connection systems by integration of passive elements into a busbar

This paper proposes an improvement of the flat connection system (busbar) used inside power converters. When a machine is fed by an adjustable speed drive (ASD), the high slew-rate voltage pulses of the power converter create additional constraints in the machine winding insulation. Electric field spikes appear in the turn insulation, specially in the first turns of the winding ; they cause an earlier ageing. The high slew-rate current pulses inside the busbar create also electromagnetic perturbations in the vicinity of the connection system and around the machine. This study focuses on the limitation of voltage and current slopes and, consequently, on the reduction of the electromagnetic emissions (EMI). The proposed optimization is obtained by inserting passive elements into the busbar: plane capacitors made with ferroelectric materials allow to control voltage slopes and an inductive zone made with a ferrite magnetic circuit acts on current slopes. Additional dissipative elements, placed on the capacitive and inductive elements, allow to reduce the switching oscillations. The mitigation of the voltage and current steep slopes improves the EMI of the connection system and the machine.