Synchronous motor drive system and synchronous motor

摘要

In sequentially selecting and driving two phases of the three-phase stator windings of a synchronous motor, detect a speed electromotive voltage of a de-energized phase, relate the speed electromotive voltage to rotor position information beforehand, then count rotor position information backward based on the detected the speed electromotive voltage to estimate rotor position; and then detect rotation speed from the change rate of the rotor position information so as to achieve highly accurate position and speed control.

主权项

1. A synchronous motor drive system comprising
an inverter connected to a three-phase synchronous motor and comprised of a plurality of switching elements, and a controller for selecting two energized phases of the three-phase windings of said three-phase synchronous motor and controlling the energization of said inverter according to six different energizing modes by means of pulse-width modulation; wherein said controller comprising an energizing mode switching means for detecting at least either a terminal voltage of a de-energized phase of said three-phase windings or a connection point voltage of a stator winding of said three-phase synchronous motor and sequentially switching said energizing mode according to the detected voltage, and a rotation count computing means for retaining an instantaneous value one or more samples earlier of an instantaneous voltage which is detected on a predetermined sampling period, calculating a difference value between said voltage retained at the time when the sign of said detected voltage was inverted and a currently detected voltage, and calculating the number of rotations of said three-phase synchronous motor based on the difference value, in an area where the rotation speed of said three-phase synchronous motor is from zero through low speed.