| abstract |
There is a high frequency voltage superimposing method as a method for obtaining magnetic pole position information of an electric motor having electric saliency without using a position sensor, and noise and torque ripple caused by the method are reduced. A plurality of voltage waveform patterns are prepared, and a pattern selected at random with the passage of time is used as a high-frequency voltage, or in a direction parallel to a magnetic flux vector interlinked with a stator winding of an electric motor. The high frequency voltage is superimposed, or the amplitude of the high frequency voltage is adjusted according to the absolute value of the time derivative of the torque command. [Selection] Figure 1 |