Partial Discharge Behaviors in Power Modules Under Square Pulses With Ultrafast dv/dt

The unprecedented high-speed switching of wide bandgap power devices may change the partial discharge (PD) behaviors of power modules, busbars, and loads. However, very little research has been published on PD behaviors under square-wave pulses with ultrafast dv/dt. To address this problem, this article studies the PD behaviors of direct bonded copper samples with different trench distances and chamfer radii under single and repetitive square pulses with ultrafast dv/dt. The results show that for the single-pulse excitation partial discharge inception voltage (PDIV) decreases with increasing rise time if the pulsewidth is shorter than 300 μs, and PDIV decreases with increasing pulsewidth. For repetitive pulse excitation, PDIV increases linearly with trench distance if the chamfer radius is larger than 0.5 mm, while it follows a concave curve if the chamfer radius is less than 0.5 mm. On the other hand, for a fixed trench distance, the PDIV changes quadratically with the chamfer radius increasing from 0 (right angle) to 0.7 mm. Based on the experimental results, a PD model with bubble expansion theory is to explain the PD mechanism under ultrafast dv/dt excitation, and an empirical equation for PDIV prediction is also derived.