A permanent magnet synchronous motor (PMSM) rotational angle sensorless control system can have a problem with restarting when coasting. A coasting restart method has been proposed that uses the information of the three-phase short circuit current. However the coasting restart conditions of the one-time three-phase short circuit method have not been revealed. This study examined the restart conditions for a rotational angle sensorless PMSM when coasting. In the experimental tests, the duration of the three-phase short circuit was varied to examine its effect on the estimated rotor angle and rotor speed. The experimental test results were numerically analyzed to quantify the effect of the short circuit duration, because the error was caused by linearization of the estimation equation. We propose an enhanced method that considers the time response of the three-phase short circuit current. The proposed method was verified experimentally.
ASJC Scopus subject areas