Study on the Non-random Characteristic of PETT Oscillation

Plasma Extraction Transit Time (PETT) oscillation in large power IGBT module, which is caused by space charge effect, causes serious electromagnetic interference to space environment and driver system. In order to investigate whether the PETT oscillation occurs randomly or not, the small signal behaviors of a simplified IGBT model is analyzed. Theoretical analysis indicates that PETT oscillation does not occur randomly, but has a strong relationship with DC bus voltage. Experimental results show that test voltage has an obvious influence on initial oscillation time, which verified the correctness of the theoretical analysis.