Failure analysis of a high voltage system by probing on the low voltage side

By probing the primary centre tap voltage of a transformer in a high voltage generator employing closed loop control a distinction can be made between the transients of breakdown events occurring either at the rectified HV output or at the transformer secondary side. The criterium is the speed of decay of the centre tap voltage. The method has been developed for a potted HV system generating 36 KV for the Faint Object Camera (FOC) for the Space Telescope. Computer simulation of the break-down and experimental simulations using the engineering model system have been performed and are reported. Comparisons with observed transients of a system breaking down are made.