1 Introduction
2.1 Structure of proposed three-phase PM motor
Recently, as an AC adjustable speed motor, the
permanent magnet synchronous motor (PM motor) driven
by an inverter is researched from the standpoint of
controllability, maintainability and high efficiency. Though
the rotor position detection is important to the control of
the PM motor, the position sensorless control of the PM
motor progresses to satisfy demands of low cost and
compactness. In particular, the rotor position estimation at
the stand-still mode is a problem, because the speed
electromotive force at the rotation is unavailable.
The estimation method utilized the magnetic saturation
of the stator core have been proposed [l]. But, the decrease
of the pilot current is necessary so that problem of noise
and vibration exist at the estimation. Also, several estimation