Calculation Method of the Thermal Field of a Power Toroidal Transformer

The paper discusses the method for calculating the thermal field of a powerful toroidal transformer for flash butt welding of pipes. This method was developed on the basis of an experimental study of the thermal field of a typical toroidal transformer KSS-01 for flash butt welding of pipes. The calculation of the thermal field is carried out in the absence of welded pipes and metal struc- tures that ensure the movement of welded pipes. The method is based on 2D models of the electromagnetic and thermal fields of the transformer. In addition, the averaged thermophysical parameters of some elements of the models are used. The averaged thermophysical parameters and heat transfer coefficients were found from the results of an experimental study of the thermal field of the transformer. To calculate the losses in the windings, the equivalent circuit of a three-winding transformer is used. The results of calculating the currents in the windings and the losses in them are confirmed by the short circuit experiment. Calculations of the thermal field of the KSS-01 transformer made it possible to identify defects when filling the transformer with a compound. These defects led to unacceptable overheating of the primary winding. The developed method was used in the design of KSS-04 transformer which is more powerful than KSS-01 transformer. The defects of filling the transformer with the compound which were seen in KSS-01 were eliminated in transformer KSS-04 and therefore the permissible heating temperatures of KSS-04 were ensured.