Abstract: A control apparatus for controlling a three phase load apparatus. The control apparatus includes a voltage source inverter having a first pair of transistors, a second pair of transistors, and a third pair of transistors. Each such pair of transistors is connected serially between the terminals of a voltage source. The activation of a first transistor in each such pair of such transistors is effected by the application thereto of a first activation voltage, a second activation voltage and a third activation voltage, respectively, causing a first phase voltage, a second phase voltage and a third phase voltage, to be applied to a respective one of the three parts of the three-phase load apparatus. The selection and duration of activation of such first transistors during each of a continuing series of equal time periods T.sub.p is symmetrical about the mid-point of each of the time periods, and is represented by six non-zero vectors and two zero vectors.