Dynamic Electro-thermal Characteristics and Damage Analysis of Pulsed Thyristor

Shortening the initial pulse width is significant to pulse generators based on multiple-stage compression. However, pulsed thyristors are damaged even if the working condition is lower than its rated parameters under ten-microsecond pulses with repetitive frequency. Based on the mixed circuit and device simulation, the temporal and spatial variation of current spreading and temperature in the thyristor were studied considering the current rise rate di/dt and pulse width. The effect of working voltage was explored, and the utilization rate of the cathode was analyzed. The development process of damage in the thyristor was investigated by analyzing the morphology of erosion points and their elements. The results show that the current crowding between the amplifying gate and the cathode is caused by the emitter short under the ten-microsecond pulse. The current rise rate di/dt does not affect the peak of global maximum temperature under the same energy loss. By contrast, the current spreading is less affected by the emitter short, and lower global maximum temperature and higher cathode surface utilization occur under hundreds of microseconds. The local and global maximum temperatures increase with the increasing working voltage. The damage of the thyristor starts from the region near the cathode and develops towards the anode. It is suggested that the erosion point between the amplifying gate and the cathode may be caused by thermal fatigue. These results can guide the application and design of pulsed thyristors in multistage compressed pulse generators.