Design of an active load for electronic welding machines

The paper presents the design of an active load for electronic welding machines. The active load´s main purpose is to reduce the amount of electrical energy that is wasted during the welding equipment burn-in tests, allowing a large fraction of it to be re-circulated through the utility grid. The converter needs to operate with low input voltages, typically a few tens of Volts, and high input currents, up to 250 Amperes. In addition, it has to guarantee galvanic isolation and a relatively large step-up ratio, so as to allow active power injection into the grid. To comply with these requirements, a multi stage solution is devised. The paper discusses the design choices, the sizing procedure and the control strategy of the more critical converter component, i.e. the step-up, front-end stage. This is represented by a six phase interleaved boost converter, operating in discontinuous conduction mode (DCM). To demonstrate the validity of the implemented solutions, experimental results from a full power prototype of the dc-dc converter are provided.