Patent ID: 7084603

Claim:
A motor control device used for controlling a motor having a rotor, comprising: an inverter that outputs a current for application to a motor; a current controller that outputs a voltage, representable as a wave, based on the current output by the inverter; a high frequency wave superpositioner that superpositions a high frequency wave on the voltage output from the current controller, the superpositioned high frequency wave used for inferring a position of a rotor in the motor; a high frequency wave setter unit that provides the superpositioned high frequency wave to the high frequency wave superpositioner, the high frequency wave setter varies at least one characteristic of the superpositioned high frequency wave; a first rotor position inferring circuit that analyzes a component of frequency of the current output from the inverter, and outputs a first inferred rotor position; a second rotor position inferring circuit that detects an induced voltage generated in a rotor of the motor, and outputs a second inferred rotor position; and a switch that selects the first inferred rotor position or second inferred rotor position.