An Improved High Voltage Winding Internal Shielding Structure With Lower Eddy Loss for Medium Voltage High-Frequency Transformer

Electric field shielding structures are commonly used to solve the problems of electrical stress binding, softening, and casting yield of high power density medium voltage high-frequency transformers. Previous studies mainly focused on the electric field shielding effect and analyzing the electrical stress on insulation layers. In this letter, the high-frequency additional power loss effect of the multiple-layer shielding structure is investigated. An analytic model for the eddy current loss of the shielding structure at high frequency is established. Based on the loss model an improved shielding structure is given to minimize the additional loss caused by the shielding structure while ensuring the shielding effect. Through insulation testing and loss comparison of the prototypes with different shielding structures, it was verified that the proposed structure significantly reduces transformer loss while ensuring shielding effectiveness.