The low temperature gating characteristics of thyristors

The gate threshold current of an inverter thyristor (1300 V, 420 A average) was measured as a function of decreasing temperature between 25 degrees C and -180 degrees C. The requirements for successful gating of thyristors are examined. It is shown that, as the temperature falls below about 225 K, the values of the theoretical alphas begin to increase. The rate of increase of the alphas accelerates as the temperature decreases. This form of the alpha suggests that it should be easier to turn the device on at lower temperatures. The measured gate current required to cause the thyristor to latch on has been shown to decrease as the temperature falls; in addition, the gate-current decreases most rapidly at the lowest temperature considered. Consequently, the measured gate current and the alphas show good qualitative agreement at temperatures below 225 K.<>