The Full-Analytical Model of AC Loss for Hollow Copper Winding in Medium Frequency Transformer

Hollow copper windings used in medium-frequency transformers can not only reduce losses, but also improve heat dissipation efficiency by passing coolant through the center of the conductor. In this article, the high-frequency ac loss of the hollow copper winding of the transformer is modeled. By decomposing the rectangular hollow copper winding with complex structure into three parallel solid copper conductor regions with regular structure, the boundary field strength and current distribution of each region are accurately solved. The effect of fill rate on loss is also considered, and then an accurate analytical model of the ac loss of hollow copper winding is obtained. The maximum calculation error is less than 9.8%. Simulation and experimentation verify the accuracy and versatility of the model.