The doctorate thesis describes various methods for Joule loss calculation in windings of resistance spot welding transofrmers. Due to the proximity effect between the individual coils of the windings, the current density distributes non-uniformly at the given operating frequencies. Non-uniformly distributed current density caused by the consequnces of the proximity effect,increases Joule loss in windings in comparison to the case, where the current density distributes uniformly. It is clearly shown that the proximity effect increases with frequency. Therefore, it is significant to determine thecurrent distribution in windings applied in further Joule loss calculation.An advanced analytical method of successive approximation, which does not take into consideration the iron core of the transformer, is developed to enable such calculations. Within the developed method, all mutualifnluences among the transformer coils are taken into consideration. Calculation of Joule loss is based on the general equation that includes current density and specific conductivity. The comparison of two methods for analytical calculation of Joule loss in transformer windings respectively the advanced analytical method of successive approximation and Dowell method showsthe significant advantages of the former. The advantage of the developed analytical method is confirmed with numerical results obtained by finite element method and experimental tests. The presented advanced analytical method of successive approximation is based on the analytical equations and, therefore enables higher level of results accuracy and less time-consuimng analysis. Moreover, it is suitable for implementation of the optimization procedures. The described analytical calculation of Joule loss is based on theparametric winding model and enables quick calculations for any transformer dimensions and operating frequencies.
D.09 Tutoring for postgraduate students
COBISS.SI-ID: 266391296The patent application describes a newly developed monitoring system (MS) for resistance spot welding system (RSWS). The MS measures, performs on-line analysis and stores all vital RSWS variables, including temperature, welding current and primary currents. It contains measurements chains, processor unit and storage unit. The sequences of stored data can be used to evaluate fitness of individual RSWS or to perform an analysis in the case of failure. The developed MS is a small stand-alone unit normally mounted on welding transformer. It can be easily modified to be suitable for other applications.
F.06 Development of a new product
COBISS.SI-ID: 17217046Dr. Vratislav Bedjanič Award for Master's thesis 2013: This work deals with the development and manufacturing of controller board for a middle frequency resistance spot welding system. It includes design and manufacturing of the electronic component parts required for data acquisition and for inverter control. The developed controller board is built around a powerful digital signal controller TMS320F28335 that can be graphically programmed in Matlab/Simulink. The applied welding transformer control algorithm considers magnetically nonlinear behavior of transformer’s iron core. In order to control the level of saturation in the iron core a saturation level sensor was developed. When applied in combination with the control algorithm running on newly developed controller board, the saturation level sensor on the one hand prevents the iron core from becoming saturated while on the other hand it makes possible optimal utilization of the iron core. Experimental results obtained with the developed controller board, control algorithm and saturation level sensor, have shown, that when applied together, they can improve operational properties of a closed-loop controlled resistance spot welding system.
E.01 National awards
COBISS.SI-ID: 17346582