Patent ID: 8106619

Claim:
A position sensorless controller, for a permanent magnet motor, that carries out a vector control calculation for controlling an output frequency and an output voltage of an electric power converter for driving the permanent magnet motor, an axis error estimating calculation for estimating axis error that is a difference between an estimated phase value obtained by integrating an estimate speed value of the permanent magnet motor and a phase value of the permanent magnet motor, and a speed estimation calculation for controlling an-estimated value for the axis error so that the estimated value matches a commanded value for the axis error, wherein, in the axis error estimating calculation, a commanded voltage value for vector control, a detected current value or estimated current value, an inductance value for a motor constant, an induced voltage constant, and an estimated speed value or commanded speed value are used to estimate the information about axis error, wherein, in the axis error information estimating calculation, a d-axis commanded voltage value, which is an output in the vector control calculation, is added to a product of three signals, which are the q-axis detected current value or the commanded current value, the inductance value, and the estimated speed value or the commanded speed value, and then a resulting value is divided by the product of the commanded speed value and the induced voltage constant.