Abstract:
For protecting a rectifier unit including a control pulse amplifier composed of a monostable multivibrator and an OR-gate, the gate being controlled by control pulses to cause the amplifier to transmit a signal to the control electrode to render it conducting, a transformer in the conductor for the rectifier is provided which makes the control pulse amplifier operative to emit a control signal in response to a flow of current in the conductor produced by an external flashover occurring when the rectifier is not conducting.