GTO driving and protection technique with status monitoring

Self-commutated converters can be simplified considerably and improved by the use of GTO thyristors. An advanced gate driving and protection concept characterized by identifier circuits in the gate driving system is described. There are a number of advantages in knowing the momentary switching states of the GTOs in a converter circuit. Gate driving can be optimized for the highest possible level of operating safety and dangerous switching states avoided. In the event of a fault, additional protection functions can be activated for effective limitation of secondary damage, and the identifier circuits also detect defective GTOs, which provides extra information for fault diagnosis. For this purpose the gate drive unit contains, in addition to the basic functions for gating the GTOs, function blocks for the identification of switching states and for the adaptive interlocking of the firing pulses in an inverter, as well as a protective firing circuit to meet the contingency that during turn-off the current has already reached a value high enough to jeopardize the GTO. The protection concept for the GTOs decisively affects economic inverter dimensioning. The aim is to interrupt operation only under extreme fault conditions (defective components) and to minimize secondary damage. Passive protection is supplemented by active measures derived from the status signals