To perform speed control, unit low speed is reached by reducing torque ripple.

Within a section of an electrical angle of 60 degrees, which is formed by dividing an electrical angle of 180 degrees by '3' or the number of phases, phase control pulses g4, g5, g6 with one pulse width, which extend in proportion to a velocity deviation by a velocity deviation signal generating part 4 symmetrically about the central position (a position at an electrical angle of 30 degrees) in the section, are generated and outputted by a phase control part 5. East changing current can be prevented from flowing through electric wires W1, W2, even when FETQ4, Q5, Q6 reverse from on to on respectively, permit gentle rise current to flow through the electric wires W1, W2, thereby preventing generation of large unwanted radiation noises and performing speed control, until low speed is reached.