How to identify the cause of thyristor​ damage?

How to identify the cause of thyristor damage?

When the thyristor needs to be inspected and analyzed for its cause after being damaged, the tube core can be removed from the cooling jacket, the core box can be opened, and the chip can be removed to observe the traces of damage to determine the cause. Analyze several common phenomena as follows:

(1) Voltage breakdown. The thyristor is damaged due to its inability to withstand voltage, and there is a smooth small hole in its chip that sometimes requires an magnifying glass to be seen. The reason may be a decrease in the withstand voltage of the tube itself or a breakdown of high voltage generated when the circuit is disconnected.

(2) Current damage. The trace feature of current damage is that the chip is burned into a pit, rough, and located far from the control electrode.

(3) The current rise rate is damaged. Its traces are the same as current damage, and its location is near or on the control pole.