Design and reliability of 2 kV, 10 kA pulse rated GTO amplifiers for fusion applications

The author describes how, in order to control the vertical position of a plasma in a fusion experiment, a gate turn off thyristor (GTO) bridge was constructed to apply a bipolar voltage of up to 2kV to a control coil. This was designed to rapidly control 10 kA of current supplied from a capacitor bank. The response time of the applied voltage was tobe less than 50μs so that the GTO was considered an ideal device for this application in terms of its switching speed and blocking voltage capability. As the maximum switchable current capability of each GTO was 3kA, a number of GTOs were connected in parallel to achieve the switchable current rating required