Calculation of copper losses in resistance spot welding transformer with space- and time-dependent current density distribution, FEM and measurements
Purpose ‐ So far the proposed analytical methods for calculation of copper losses are rather simplified and do not include the time component in the basic partial differential equations, which describe current density distribution. Moreover, when the physical parameters of the transformer (wire dimensions) are out of the certain range, the current density distribution approaches infinity. The purpose of this paper is to offer a generally applicable analytical method. The main goal of the proposed modification of the solution to the current density is improvement of the accuracy and stability of the analytical results. Design/methodology/approach ‐ This paper deals with the calculation of copper losses with various methods, which are based on a time-dependent electromagnetic field. Analytical method is based on Maxwell equations and Helmholtz equation. Numerical calculation is performed with finite element method (FEM). Findings ‐ Analytical method is a very accurate and it gives results, which are very similar to the actual behaviour of the current density in the winding. However, the FEM analysis is easier to comprehend, but yet very dependent on input parameters. Research limitations/implications ‐ The numerical analysis may not be accurate enough, because of the problems with the oscillation of the output welding current amplitude. To calculate copper losses correctly, the output welding current must be equal in all test cases, especially during the measurements. Originality/value ‐ When the physical properties exceed a certain range, the copper losses of the analyzed welding transformer cannot be calculated with existing analytical methods. The new analytical approach gives a far more realistic solution to the current density distribution and improves the accuracy and stability of the results.
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