Abstract: The present method and circuit arrangement control the r.p.m. of a three-phase motor connected in a star or Y-circuit by sensing current variations in the star point of the motor windings. These current variations are converted into voltage variations which represent the current input of the motor windings. These voltage variations are used to control the duration of the application of the operating voltage to the motor windings for varying the motor r.p.m. The circuit for this purpose includes a controlled diode circuit arrangement connecting the motor windings to the star point and a control or drive circuit for controlling the diode circuit arrangement The drive circuit makes the diode circuit arrangement conductive for predetermined time durations which depend on the voltage variations. These time durations are also manually adjustable in an open loop control, whereby a closed loop control is provided in combination with an open loop control.