| 摘要 |
<P>PROBLEM TO BE SOLVED: To avoid the generation of an overcurrent trip and the deterioration of efficiency by canceling the displacement of a phase between an inverter output voltage and a motor back-electromotive voltage by a relatively simple constitution, and by preventing an overcurrent from flowing to a switching element of an inverter. <P>SOLUTION: A motor current is detected by a current detector 11, and a differential value between a transient build-up current and a fall current value of the motor current is obtained. A phase shift circuit 12 shifts the phase of a magnetic position detection signal according to the differential value, and makes the phase of the output voltage of the inverter 2 and the phase of the motor back-electromotive voltage nearly coincide with each other, thus avoiding an excessive motor current flowing caused by the phase difference of both the voltages. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
