Mapping Electric Fields in Insulation System of High Voltage Planar Converter Transformer
A concept of a planar high voltage converter transformer is proposed where a magnetic core is surrounded by a stack of multiple secondary windings implemented as traces etched on PCBs with integrated rectifying elements. The rectified outputs are connected in series to achieve the required high dc voltage. The modular solution of the secondary winding reduces complexity, size, material requirements and costs also facilitating the construction and assembly procedures. However, it introduces additional stress on the insulation system due to the dc offset voltage and superimposed high frequency voltages induced by switching operations. In the present study, the electric field patterns and its strength levels that stress the insulation system are identified and quantified by means of computer simulations. The results of the simulations are presented and discussed in the paper. Based on the performed analysis, a prototype of the transformer $(90 \text{kV} / 0,4 \mathrm{A} / 36 \text{kW})$ was built and successfully tested. Specific features of the simulations are outlined.