Magnetic pole position detector for synchronous motor

A magnetic pole position detector for detecting a magnetic pole position when a synchronous motor is started, the magnetic pole position detector comprising:

• a voltage command unit that generates high-frequency voltage command in a dq coordinate system;
• a three-phase coordinate transformation unit that transforms the high-frequency voltage command in the dq coordinate system to high-frequency voltage command in a three-phase coordinate system by using an estimated magnetic pole position;
• a current detection unit that detects three-phase current fed from a power converter to the synchronous motor, the power converter generating drive power for the synchronous motor in accordance with the high-frequency voltage command in the three-phase coordinate system;
• a dq-coordinate transformation unit that transforms the three-phase current detected by the current detection unit to current in the dq coordinate system by using the estimated magnetic pole position used in a transformation by the three-phase coordinate transformation unit;
• an estimated magnetic pole position calculation unit that calculates a new estimated magnetic pole position to be used in a coordinate transformation process by each of the three-phase coordinate transformation unit and the dq-coordinate transformation unit, in accordance with the current in the dq coordinate system and the high-frequency voltage command in the dq coordinate system;
• and
• a magnetic pole position confirmation unit that confirms that, when the estimated magnetic pole position calculated by the estimated magnetic pole position calculation unit substantially converges on a certain position, the estimated magnetic pole position is the magnetic pole position when the synchronous motor is started.