For measuring the delay angle in a static converter, a rampfunction generator is provided for each rectifier phase connected to the alternating current network. The ramp-function generator includes a timing device responsive to passage through zero of the commutation voltage derived from the network, and a connecting member which connects the ramp-function generator to a sensing and holding circuit. The connecting member is controlled by the control pulse device of the converter so that the signal stored in the sensing and holding circuit at any moment corresponds to the delay angle for the rectifier last ignited.