Abstract: A storage section stores, as stored current values, currents flowing when a voltage application section applies voltage vectors to a three-phase rotary machine. A position estimation section estimates the rotor position of the rotary machine in a stopped state based on the stored current values. An adjustment section adjusts a minimum necessary application time that allows the rotary machine to be magnetically saturated by voltage vector application, to enable rotor position estimation. Further, the adjustment section uses, as an adjustment evaluation value, the magnitude |?Y| of differential admittance obtained by dividing a summed current value calculated from the stored current values by the voltage amplitude value of the voltage vector instruction when the voltage vector based on the voltage vector instruction is applied with the application time being set at an arbitrary application time, and adjusts the application time based on |?Y|.

Abstract: A storage section stores, as stored current values, currents flowing when a voltage application section applies voltage vectors to a three-phase rotary machine. A position estimation section estimates the rotor position of the rotary machine in a stopped state based on the stored current values. An adjustment section adjusts a minimum necessary application time that allows the rotary machine to be magnetically saturated by voltage vector application, to enable rotor position estimation. Further, the adjustment section uses, as an adjustment evaluation value, the magnitude |?Y| of differential admittance obtained by dividing a summed current value calculated from the stored current values by the voltage amplitude value of the voltage vector instruction when the voltage vector based on the voltage vector instruction is applied with the application time being set at an arbitrary application time, and adjusts the application time based on |?Y|.

Abstract: The present invention provides an apparatus for and a method of compensating an output voltage error of an inverter that changes direct current (DC) power into alternating current (AC) power. More specifically, the present invention provides an apparatus for and a method of compensating for an output voltage error by detecting the polarity of output current from an inverter used to change DC power into AC power. In accordance with one embodiment of the present invention, a current detector is used to detect the output current of the inverter circuit. A polarity discriminating device, receiving the detected output current, sets a threshold current value that is to be used to accurately determine the polarity of the output current. As the output voltage error has the same phase but is opposite in polarity relative to the current output by the inverter, an accurate detection of the output error can be made by accurately detecting the output current polarity.