METHOD AND DEVICE FOR DRIVING STEP-BY-STEP ELECTRICAL ROTARY MACHINE

An electrical rotary machine comprising a stator and a rotor may be used as a step motor when the outputs of a digital phase modulator comprising a clock pulse generator and pulse number reducing circuits each comprising a chain of flip-flops connected in series are applied to the stator and the rotor windings through an inverter respectively to generate the rotating magnetic fields. In response to a number of rotation command pulses to be inserted in a clock pulse train from the clock pulse generator and to a manner by which the command pulses are inserted into the clock pulse train, a number of steps and the direction of rotation of the rotor can be controlled. The angle of rotation of the rotor in response to one command pulse may be varied by varying a number of series-connected flip-flops in the pulse number reducing circuit.