Thyristor Use at Low Temperatures

The parameters of power electronic devices such as thyristors and diodes are closely related to the environmental conditions of their chips. When working in high altitude and low temperature environments, users should pay attention to reasonable use to ensure reliable operation of the devices.

In the thyristor factory parameter marking values, the blocking voltage, leakage current, di/dt, dv/dt and other parameters refer to the test values ​​under the rated junction temperature conditions, and these parameters can still guarantee the performance at low temperatures; Trigger current and gate trigger voltage are test values ​​at 25°C. They generally decrease with increasing ambient temperature and increase with decreasing temperature.

Therefore, when using at high altitude and low temperature, it is necessary to pay attention to:

1. Under the condition of -40°C, the thyristor gate trigger current value will be doubled at 25°C, and the gate trigger voltage will increase by about 30%. Therefore, to ensure the reliable start-up of the equipment, a thyristor gate trigger current of sufficient strength is required. That is, we require users to use strong trigger measures. Strong triggering also plays an important role in improving the device's di/dt performance, reducing turn-on time and turn-on loss, and facilitating serial and parallel operation of the device. The recommended gate trigger conditions are: gate trigger current amplitude IG=10IGT (2-5A, <10A); gate current on time tr≤1μs; gate trigger current rise rate: di/dt≥2A/ Μs.

2. At high altitudes, the cooling capacity of air-cooled radiators will be reduced, but the lower environmental stability will be conducive to device heat dissipation. Therefore, in consideration of the maximum ambient temperature that may occur in the field, the device and the radiator must be considered during use. Choose to leave a certain amount of current margin.

3. If the device is started and stopped very frequently, the device frequently cycles at temperatures between -35°C and 125°C. The life and reliability of the device will be lower than during normal operation. Attention should be paid during use.