Online Monitoring Local Junction Temperature of High-Power Thyristors Based on Peak Stray Gate Current

The non-uniform current distribution in high-power thyristors leads to a significant rise in local junction temperature (Tlj), potentially threatening the reliability of high-power thyristors. For online monitoring Tlj, a novel temperature-sensitive electrical parameter (TSEP) method was proposed based on peak stray gate current (ipsg). First, simplified turn-off models for high-power thyristors with an amplifying gate were set up to explore the variations of gate-cathode voltage and stray gate current in the turn-off transition. Subsequently, the theoretical relationship between ipsg and Tlj was established. Significantly, the physical meaning of Tlj was illustrated by the theoretical relationship and the temperature distribution simulation. Next, the feasibility of the proposed method was verified by the temperature calibration experiment. Considering self-heating, the temperature sensitivity is 89 mA/℃ at a thyristor voltage of 1.0 kV, which increases with increasing thyristor voltage. Finally, an online monitoring Tlj case was carried out based on a tunnel magnetoresistance current sensor. The proposed method is easy to implement and is capable of measuring local junction temperature concerning major heat generation regions, which is suitable for high-voltage applications.