Development of a compact 750KVA three-phase NPC three-level universal inverter module with specifically designed busbar

This paper presents the bus bar design of a 750kVA three-phase Neutral Point Clamped three-level universal inverter module (PEBB) of high power density. ANSOFT Q3D is used in comparative evaluation for three types of multi-layer bus bar structures and a novel low inductive laminated configuration with divided connections is proposed for this inverter modules. Combined with specially arranged snubber capacitors distribution, reduced voltage overshoots across IGBTs at turned-off and lower loss within the electrolytic capacitors are achieved without any RC snubbers, along with optimized high frequency current equalization. The stray inductance of the bus bar is simulated as a contrast to the test results. Feasibility and improved performance are confirmed by experiments.