Cyclically controlled electrical equipment having a control angle which is variable over a portion of the operating cycle

Electrical converter equipment for the supply of electrical current to at least one d.c. load comprising:

• a controllable converter connected to an alternating voltage source, said converter having a by-pass path for the direct current, control means for controlling the direct voltage of the converter by influencing the control angle of the converter, the control means operating cyclically such that each operating cycle comprises a plurality of half-periods of the alternating voltage of the alternating voltage source and that the converter within at least part of the control range operates with different control angles during the different half-periods of a cycle, wherein each of said cycles comprises n periods of the alternating voltage of the source, n being an odd number not less than three, said control means, during two of the half-periods of the cycle controlling the converter with a control angle which is variable for influencing the direct voltage of the converter and, during each of the other half periods of the cycle, controlling the converter with a fixed control angle, and the half-periods during which the converter is controlled with said variable control angle being time equidistant.