METHOD FOR JUDGING MAGNETIC POLARITY OF SYNCHRONOUS MOTOR AND CONTROLLER FOR SYNCHRONOUS MOTOR WITH MAGNETIC POLARITY JUDGING FUNCTION

摘要

PROBLEM TO BE SOLVED: To provide a controller for a synchronous motor having a function to judge a magnetic polarity with ease. SOLUTION: The controller is equipped with a current detection and 3/2 converter 7 which detects the current value of the d axis and q axis in the synchronous motor 10, a current command pulse generator 11 which outputs a positive and a negative current command pulse big enough to cause flux saturation as the d axis current, and a magnetic polarity judging device 12 which executes a magnetic polarity judgement based on the amplitude in the d axis current obtained from the current detection and 3/2 converter, when the positive and negative current command pulses are applied to an estimated position, after the magnetic pole position at the time when the synchronous motor stands still is estimated. Especially when a big current amplitude is detected by applying the positive current command pulse, while a small current amplitude is detected by applying the negative current command pulse, the estimated magnetic pole position has no error. When a small current amplitude is detected by applying the positive current command pulse, while a big current amplitude is detected by applying the negative current command pulse, the estimated position of the magnetic pole is judged to be 2.