Seventy Years of Rajchman Measures

A control system for a tap changer using a vacuum interrupter. The control system has provisions for monitoring the vacuum interrupter to detect any failure of such interrupter and thus prevent further operation of the tap changer. Should the interrupter fail to open on a tap change, the tap changer motor is reversed returning the changer to the starting position and locking the changer. Should the interrupter be open at the start of a tap change, the tap changer is reversed returning the tap changer to the starting position and then locking the tap changer. In another embodiment, should the interrupter fail to close after a tap change has been initiated, the tap change is completed and the changer locked in that position.