Abstract: A motor control apparatus and a motor unit having such a motor control apparatus according to the present invention are constructed to detect a terminal voltage for switching elements of the same phase in a dead time period by a voltage output circuit 10, and to detect the instant when the sign of a phase current changes from the detected terminal voltage by a current sign change detection part 11. Based on the phase of a current sign change timing provided from the current sign change detection part 11 and the phase of a phase applied voltage, the first applied voltage control circuit 14 generates a phase applied voltage command to a switching element modulation circuit 9. Such arrangement makes it possible to provide motor continuous energization or motor energization drive near to 180 degrees at high efficiency, without the provision of any current sensors.

Abstract: A method for readily measuring each motor parameter with high precision, with an induction motor at rest, and an apparatus for controlling the induction motor using these motor parameters are provided. The induction motor is set to a single-phase feed state or a feed state equivalent to that state. First, a stator resistance is measured from a current value and a voltage value at the time when a direct current command is given. Then, the current command of a current having an appropriately high frequency and a known current differential value is given to find a rotor resistance and a leakage inductance from current values and voltage values at two different times and the previously obtained stator resistance value. Then, the current command of a sine wave current having an appropriately low frequency is given to find a mutual inductance using the current value and the voltage value at the time. These measured values are used for a slip frequency operation and a speed estimation operation.