PURPOSE: To obtain a motor having a high efficiency at a high speed by controlling to conduct only by one switching element inserted to an exciting coil, supply to charge heat storage magnetic energy in a small-capacity capacitor when the conduction is stopped at an end, and holding a high voltage.

CONSTITUTION: A capacitor 47a having a small capacity, a diode 21a and semiconductor elements 4a, 4b, 5a, etc., are provided, and only one of switching elements 20a, 20b, 20c of exciting coils is used at a negative voltage side of a power source. When conduction is stopped at an end, magnetic energy stored in an exciting coil 32a is charged in the capacitor 47a as a high voltage through the diode 21a and held. Then, when the coil 32a is again conducted, applied voltages are both the charging voltage of the capacitor 47a and the voltage of the power source. Accordingly, a rise of the current of the coil 32a becomes abrupt. As the discharging of the capacitor 47a is finished, generations of reduced torque and opposite torque are removed, and a motor having a high speed and a high efficiency is obtained.