| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an AC motor drive system in which estimation precision of rotor position, rotational speed and rotational direction is enhanced even when the idling speed is low, and detection precision of DC input current is also enhanced. <P>SOLUTION: The AC motor drive system for driving a motor with n-phase field by means of an n-phase inverter performs a switching operation for providing an on signal to one switching element and providing an off signal after a predetermined period, and a current detection operation for detecting DC current of the inverter by a current detection means following to the switching operation, and comprises a means for estimating at least one of the rotor position, rotational speed and rotational direction of the motor based on the detection value of the DC current wherein the on period of the switching element in the switching operation is determined based on a known rotational speed or speed range of the motor. <P>COPYRIGHT: (C)2007,JPO&INPIT |
