A New Quantity to Describe Power Semiconductor Subcycle Current Ratings

A new quantity for predicting the subcycle surge current ratings of silicon diodes and thyristors is presented. The quantity I
²
√t is shown to be much more valid than the more conventional I
²
t rating in coordinating power semiconductors with fast-acting current-limiting fuses. The requirement of the device to block reverse voltage on the next half-cycle following the surge current is reviewed and shown to be quantitatively significant in the subcycle current capability of power semiconductors.