BRUSHLESS MOTOR CONTROL APPARATUS AND BRUSHLESS MOTOR CONTROL METHOD

Even in a situation other than engine normal operation such as engine stall, the output voltage of the three-phase brushless motor is prevented from causing the excessive voltage to be applied to an external load. [0002] A brushless motor control apparatus (10) of the present invention calculates the number of rotations of an engine based on a cycle of zero-cross points of the phase voltage Vsu induced to a sub-coil Su of a three-phase brushless motor (1). Then, when the number of rotation of the engine is smaller than the first number of rotations N1, before it becomes impossible to detect the zero-cross points, the control state of the three-phase brushless motor 1 is changed from the state of phase control by a phase control regulator unit (24) with respect to the AC output voltages Vu, Vv, and Vw to the state of interphase short circuit of motor coils by a short regulator unit (25). Then, when the number of rotations of the engine exceeds the first number of rotations No and the phase voltage Vsu becomes the voltage level such that the zero-cross points can be detected, the control state is changed again to the state of phase control by the phase control regulator unit (24).