Patent ID: 7598698

Claim:
A motor control device comprising: a current detecting portion that detects phase current of one phase among three phase currents supplied from an inverter to a motor; a current estimator that estimates phase current of phases other than the detected phase current by using a specified current value indicating current to be supplied to the motor, and derives control current corresponding to the specified current value from the estimated phase current and the phase current of one phase, wherein the motor control device controls the motor via the inverter so that the control current follows the specified current value, and wherein a first axis is a rotation axis corresponding to a direction of magnetic flux generated by a permanent magnet provided to a rotor of the motor, and that a second axis is a rotation axis orthogonal to the first axis, the specified current value is made up of first and second specified current values that are a first axis component and a second axis component of the specified current value, the control current is made up of first and second control currents that are a first axis component and a second axis component of the control current, the current estimator includes a coordinate conversion portion that converts the first and second specified current values into three phase specified current values with respect to the three phase currents based on a detected or estimated rotor position of the motor, and the current estimator estimates phase current of phases other than the phase current detected by the current detecting portion, by using the three phase specified current values, and derives the first and second control currents by coordinate conversion on three phase currents based on the estimated phase current and the phase current detected by the current detecting portion, based on the rotor position.