Pulse controllers

A pulse controller for controlling the mean current supplied to each of a plurality of d.c. loads, comprising a plurality of main thyristors for connection in series between respective loads and a d.c. source, a common commutating capacitor, a plurality of commutating thyristors connected with respective main thyristors and each connected to the commutating capacitor to form with the capacitor a shunt across the corresponding main thyristor so that firing of the commutating thyristor effects commutation of the corresponding main thyristor and subsequent forward charging of the commutating capacitor from the d.c. source, means for reversing the charge on the commutating capacitor after it has been forward charged thereby to put the capacitor in condition to commutate any one of the main thyristors on firing of the corresponding commutating thyristor, and control circuit means for controlling firing into conduction of the thyristors so that conduction of the commutating thyristors occurs one at a time at intervals not less than the time required, from the commencement of commutation of any main thyristor, to effect forward charging of the commutating capacitor and reversal of the forward charge on the commutating capacitor.