Dr. Robert Brezovnik, univ. dipl. inž., Univerza v Mariboru, Fakulteta za elektrotehniko, računalništvo in informatiko
prof. dr. Jožef Ritonja, univ. dipl. inž., Univerza v Mariboru, Fakulteta za elektrotehniko, računalništvo in informatiko

Abstract:

In the automotive industry, resistance spot welding systems are used extensively for welding car bodies, where the welding transformer is installed on a moving robot, so the weight of the transformer is an important factor. The weight of the transformer can be reduced by a higher switching frequency, as a smaller cross-section of the iron core and thus the windings can be used, which significantly reduces the weight of the transformer. However, a higher switching frequency of the transformer makes it impossible to achieve the same maximum welding current value at the same load. The paper focuses on the modelling of the resistance spot welding system and the analysis of the frequency dependence of the maximum value of the welding current at the same load. It also discusses the reasons for the loss of duty cycle and the frequency dependence of the decrease in effective duty cycle by increasing the switching frequency.

Keywords:

resistance spot welding, transformer, DC-DC converter, pulsewidth modulation, duty cycle, circuit model