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.