The Interactions Analysis for High Frequency Transformers Insulation Under Multi-Stress of High Voltage, High Frequency, and High Temperature

As a critical component of power electronic transformer (PET), high frequency (HF) transformers are subjected to multi-stress of high voltage, high frequency, and high temperature for a long time. The combined stress can accelerate the aging process or even lead to the breakdown of the insulation, thus impacting the reliability and reducing the lifetime of the system. However, the life characteristics of the insulation under the combined effect of high-frequency, high-voltage pulse-width modulation (PWM) square-wave pulses and high temperature are not yet understood, which is investigated in this paper. A high frequency PWM electro-thermal aging test platform for HF transformers insulation is developed. Aging tests are performed under multi-stress on the insulation paper which is used for the main insulation of a HF transformer. The samples are stress with PWM voltages up to 3.5 kV, frequency up to 60 kHz, and temperature up to 120°C generated by a half-bridge inverter and a temperature chamber. The experiment is design and analyzed with statistical method of response surface method (RSM) and analysis of variance (ANOVA). The main and interactions effects of multi-stress on the insulation life are evaluated. The findings contribute significantly to the understanding of the insulation life characteristics subjected to multi-stress conditions. Furthermore, the results provide valuable insights for the development of life models for HF transformer insulation.