Abstract
A method for initial rotor position estimation utilizes the dependence of inductance on the rotor position, which is caused by magnetic saturation of the iron core. The initial rotor position estimation is used to drive permanent magnet synchronous motors and generally requires information on three-phase currents. Recently, DC bus current detection has often been adopted as a low-cost method for reconstructing three-phase currents. However, the initial rotor position estimation method cannot be applied to DC bus current detection. The authors have developed a new method for initial rotor position estimation that is suitable for DC bus current detection. In the new method, high-frequency voltage waves are applied to the motor, and the initial rotor position is estimated by using the ripple components of the motor current. In this method, the applied voltage phase is changed over by 120 electrical degrees and applied to the three phases. A positive side current value and a negative side current value of a phase current produced by application of high-frequency voltage are detected from a DC bus current. The basic idea, computer simulation, and experimental results are discussed in this paper.
