Abstract: A motor control apparatus includes a phase current detecting section for detecting phase currents to a motor, a current phase/current peak value calculating section for calculating a current phase based on the phase currents, a voltage phase setting section for adding a predetermined phase difference to the current phase and setting the resultant sum as a voltage phase, a phase voltage setting section for setting phase voltages to the motor based on the voltage phase and the command voltage. Basically, the motor is operated by maintaining the voltage at constant and always monitoring the current/voltage phases so as to maintain a constant phase difference, without the motor axis position being predicted.

Abstract: A control device for a compressor motor and an inverter according to the present invention monitors the amplitude of a phase current of a three-phase DC motor. As the amplitude of the phase current approaches an overload condition of the inverter or motor, the control device decreases the rotational velocity of the motor by a predetermined rotational deceleration. By reducing the rotational velocity of the motor by a certain deceleration, the control device of the present invention ensures that the motor load, i.e., the amplitude of the phase current, does not reach or exceed an overload condition. By use of this device, it is possible to suppress or reduce effectively the frequency of motor stops caused by an increase in the phase current.

Abstract: A control device for a compressor motor and an inverter according to the present invention monitors the amplitude of a phase current of a three-phase DC motor. As the amplitude of the phase current approaches an overload condition of the inverter or motor, the control device decreases the rotational velocity of the motor by a predetermined rotational deceleration. By reducing the rotational velocity of the motor by a certain deceleration, the control device of the present invention ensures that the motor load, i.e., the amplitude of the phase current, does not reach or exceed an overload condition. By use of this device, it is possible to suppress or reduce effectively the frequency of motor stops caused by an increase in the phase current.