To start a motor without any magnetic pole sensor and control an adequate rotor angle synchronous with a magnetic pole position of a rotor, by providing a device for detecting synchronousness of rotation speed of a rotor with speed command from a speed control system after motor starting and a means for correcting the rotor angle to an adequate magnetic pole position.
A pulse signal from a rotation position detector 2 of a motor 1 is converted to a rotation speed by a rotation position speed converter 13, and a speed control device 6 outputs torque command based on a deviation between a speed command from a speed command device 11 and a speed feed- back value from the rotation position speed converter 13. A torque command current command converter 5 converts the torque command to a current command. A current control device 4 controls so that actual current is flowed according to the command based on each output from a rotor angle calculating means 7, a rotor angle correcting device 8, and a current detector 10. An inverter 3 performs PWM control according to a voltage command signal, and controls output voltage and output frequency of the inverter 3.
NOKITA AKIHIRO
ANDO TAKEYOSHI
NIHEI HIDEKI
NAGASE HIROSHI
HITACHI BUILDING SYS CO LTD
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