Eupec has shown in several tests that it is possible to integrate a forward-recovery protection into a LTT, too. Up to this time this protection function is not integrated to the standard LTT.
Commutation of a thyristor leads to an extraction of the free charge carriers in the n-base and the p-base and the formation of an anode-side depletion layer in the n-base. Since the depletion layer extends only to a certain depth into the n-base, excess carriers remain in its quasi-neutral plasma region, recombining there at a certain rate. When large regions of the thyristor have completely recovered and an uncontrolled forward voltage pulse appears, the remaining small region with excess carriers in the main cathode area may turn on. This may result in current filamentation, self-heating and, finally, in local destruction of the thyristor.
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