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

The nonuniform current distribution in high-power thyristors leads to a significant rise in local junction temperature (T_lj), potentially threatening the reliability of high-power thyristors. For online monitoring T_lj, a novel temperature-sensitive electrical parameter method was proposed based on peak stray gate current (i_psg). First, simplified turn-<sc>off</sc> 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-<sc>off</sc> transition. Subsequently, the theoretical relationship between i_psg and T_lj was established. Significantly, the physical meaning of T_lj 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/°C at a thyristor voltage of 1.0 kV, which increases with increasing thyristor voltage. Finally, an online monitoring T_lj 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.