With the development of wide-band gap semiconductors like SiC

the operational limits of power devices have been extended

increasing demands on the insulation performance of materials such as epoxy resin. This study investigates the breakdown strength of epoxy resin under 1~20 kHz bipolar square wave voltages with varying ramp rates (1

0.5

0.1 kV/s

and stepwise ramping over 20 s). Results show that breakdown strength decreases with higher frequency and lower ramp rates

with a 45.75% reduction at 20 kHz and 0.1 kV/s compared to 1 kHz. Partial discharge and thermal analyses reveal that enhanced discharge activity and heat accumulation due to dielectric loss are the primary causes of breakdown. Improving thermal conductivity mitigates thermal runaway and enhances high-frequency voltage endurance. These findings offer a theoretical basis for assessing epoxy resin insulation performance under high-frequency electric fields and present reference for insulating material design and packaging optimization.