Patent ID: 8226372

Claim:
An electric compressor comprising: a hermetic container in which refrigerant is filled; a motor having a stator and a rotor equipped with a permanent magnet, accommodated in the hermetic container; a position detection device for detecting a position of the rotor and outputting a rotor position detection signal; a controller for driving the motor; and a compressing unit accommodated in the hermetic container and driven by the motor, wherein the controller controls the motor with a feedback control, which determines a timing of turning on/off switching elements based on the rotor position detection signal, when the motor is driven a low rpm, and wherein the controller controls the motor at a 100% duty with an open-loop control, which outputs a given frequency and drives the motor synchronously with the given frequency, such that the motor operates as a synchronous motor independently of the rotor position detection signal, when the motor is driven at a high rpm.