PURPOSE: To enhance starting characteristics by providing an auxiliary stator applied with a winding and feeding a current thereto independently from the winding of main stator.

CONSTITUTION: When terminal voltage of a capacitor 102 reaches the threshold voltage of an AND circuit(LC) 103 after turn ON of power, the LC 103 outputs a waveform rising stepwise which is then differentiated through a first differentiation circuit 105 to produce a pulse for setting a flip-flop circuit(FF) 106. Consequently, output voltage from a first Hall element 10 is applied through LCs 112, 113 to power supply transistors 118, 119 which produce currents to induce flux for generating starting torque. Upon start of rotation, output voltage from the first Hall element 10 repeats H and L. Waveform of output voltage from the first Hall element 10 is then differentiated through a second differentiation circuit 109 to produce a pulse for resetting the FF 106. Consequently, current supply is interrupted for the windings 9a, 9b of the auxiliary stator 7 but sustained for the windings 8a, 8b of the main stator 6 thus sustaining rotation.