Abstract: A thyristor rectifier for a static converter is formed of a plurality of thyristors, each provided with a control device and a control circuit for the entire rectifier connected to these control devices. Detectors are provided and arrangements are provided response to the voltage over a thyristor to emit an indicating pulse to the detectors when the voltage over the thyristors amounts to a certain value. A selector is provided for sensing these pulses and for recording the indicating pulses emitted through the detectors to a counter. Control units are also provided which control and synchronize the control and counter in relation to each other.