Development of 120 kV and 60 kW Three Phase LCC Resonant Converter for Electron Beam Welding System

This article describes the development of a 120 kV and 60 kW cathode power supply (CPS) for an electron beam welding (EBW) system. Since the developed CPS is based on a three phase LCC resonant converter, it shows many superior features such as parasitic component utilization and low output voltage ripple. In addition, by adopting a symmetrical bipolar voltage multiplier (SBVM) as the CPS rectifier, the voltage imbalance among SBVM stages can be reduced even at the high output current. Therefore, the CPS can effectively achieve the output voltage of 120 kV and output power of 60 kW with low voltage stress on SBVM components. Furthermore, by using phase shift modulation (PSM) for load regulation, the conduction and switching losses are reduced in the light load operation due to the fixed operating frequency and small circulating current compared with the conventional pulse frequency modulation (PFM). For the practical use of the three phase LCC resonant converter with SBVM, several issues about the implementations of the transformer and interleaved PSM controller are addressed. The developed CPS is installed on the 120 kV and 60 kW EBW systems and the experimental results are presented to verify the performance of the developed CPS.