| 摘要 |
PURPOSE:To increase an output of a motor at the time of nonlocking by alleviating an overload judging condition during nonlocking as compared with that during locking. CONSTITUTION:Memory means 30 stores overload deciding conditions of locking and nonlocking states of a motor 10. For example, it is assumed as the condition at the time of locking that a maximum allowable current I1 continuously flows for a time t1. And, it is also assumed as the condition at the time of nonlocking that a maximum allowable current I2 continuously flows for a time t2, where I1<I2, t1<t2 are satisfied. Thus, the conditions I2, t2 at the time of the nonlocking are alleviated as compared with the conditions I1, t1 at the time of locking. Lock detecting means 32 decides whether a rotor 12 is locked or not. That is, if a current command (i) is a state of the current I1 during a period when the present position theta of the rotor 12 is continued for a predetermined time, the motor 10 is judged to be locked, a coil current is interrupted by current control means 22 to protect the motor 10. If it is judged to be non- locked, a phase controller 24 judges the load is an overload by using the conditions I2, t2 at the time of nonlocking from the means 30. |
