Series-parallel load-resonant converter for controlled-current arc welding power supply

An arc welding power supply requires the ability to limit the load current under short circuit conditions and limit the load voltage under open circuit conditions. The series-parallel load-resonant power converter is a circuit configuration which can achieve this. The potential for high frequency operation in these converters minimises the size of the magnetic components in the power converter and reduces output current ripple. The paper presents the theoretical and practical aspects of the design and construction of a series-parallel load-resonant power converter, for use as a controlled current arc welding power supply. A power converter with an output voltage of 25 V and output current of 200 A operating at 85 kHz is designed and constructed. A novel method of control of the resonant power converter is described. Output power control is achieved by using an active rectifier modulating the DC supply voltage to the power converter. Practical results of the power converter in operation supplying 200 A to a low inductance load are presented