Partial Discharge Behaviors in Power Module under Very High Dv/dt Repetitive Square Voltages

Partial discharge (PD) is more likely to happen in the power module due to the increasing switching speed of new generation semiconductors. However, little research has been done to study the PD behaviors under very fast dv/dt (above $50 \mathrm{kV}/\mu\mathrm{s}$ ) repetitive square-wave voltages. To address this problem, PD behaviors of designed direct bonded copper (DBC) samples with different trench distances and chamfer radiuses under fast dv/dt ( $130 \mathrm{kV}/\mu\mathrm{s}$ ) repetitive square voltages are studied. The results show that, for different trench distances, the partial discharge inception voltage (PDIV) increases linearly with increasing trench distances when the chamfer radius is larger than 0.5 mm, while PDIV shows a hump curve when the chamfer radius is less than 0.5 mm. The apparent charge becomes 23 nC with a large dispersion when the trench distance is 0.5 mm. For different chamfer radiuses, PDIV presents a U-shape shape curve with increasing radiuses from the zero (right angle) to 0.7 mm. The apparent charge is about 325 pC with a large dispersion when the chamfer radius is zero. The detailed experiment results and discussions are presented in this paper.