Patent ID: 7190130

Claim:
A method of detecting a magnetic pole position of a motor having electric saliency, said method comprising: generating an arbitrary high frequency in input voltages or input currents of the motor by means for producing an arbitrary phase difference between a U-phase, a V-phase, and a W-phase, in said inverter, wherein said arbitrary high frequency is not equal to an output frequency of a voltage source PWM inverter, converting said input voltages or said input currents to a first two-phase stationary coordinate system in which a U-phase of three phases of said motor is α-axis and an axis intersecting said α-axis at 90 deg. is β-axis, to generate first converted signals, detecting a first current and a second current in respective said α- and β-axes, from the first converted signals, converting said input voltages or said input currents to a second two-phase stationary coordinate system shifted by about 45 deg. from said first two-phase stationary coordinate system, axes of the second two-phase coordinate system being α′-axis and β′-axis, to generate second converted signals, detecting a third current and a fourth current in each of said α′- and β′-axes, from the second converted signals, and detecting a magnetic pole position of said motor by using said first, second, third, and fourth currents.