Magnetic Polarity Detection Method for Permanent Magnet Synchronous Motor using Inductance Variation

Abstract

This study presents a magnetic polarity detection method of an initial rotor position estimation for permanent magnet synchronous motor drives without a position sensor. The magnetic polarity detection method utilizes stator core magnetic saturation caused by the rotor magnet and uses current responses when a high frequency or impulse voltage is applied to the motor. Recently, capacity enlargement, miniaturization, and cost reduction of the motor have been steadily progressing and motors with complicated magnetic saturation characteristics are available. The authors have developed a new magnetic polarity detection method for initial rotor position estimation that is suitable for many motors having common or complicated magnetic saturation characteristics. In the proposed method, high-frequency voltage waves with different amplitudes are applied to the motor. The proposed method measures the motor current ripple components and can estimate the magnetic polarity by using the amount of d-axis inductance variation caused by magnetic saturation. The basic idea, computer simulation, and experimental results are discussed in this paper.