| 摘要 |
<P>PROBLEM TO BE SOLVED: To surely start a motor in a free run state, in an object which starts by 120° rectangular wave PWM system. <P>SOLUTION: A rotation judging circuit 26a detects the rotational direction of the motor 5, based on a rotational direction signal sh, in a non-conductive state where a selection signal sto is off. In the starting sequence from reversion where its starts the motor 5 rotating reversely by external wind, etc. received with a fan 4 in the normal direction by sensorless 120° rectangular wave drive, a 120°current application signal forming circuit 22 selects positional signals bu, bv and bw of six resolution based on the zero cross timing of induced voltage signals eu, ev and ew, and starts current application, and switches it into current application based on positional signals cu, cv and cw, at the point of time when it becomes possible to accurately detect the positional signals cu, cv and cw of six resolution based on the comparison between voltages Vu, Vv and Vw and neutral voltage Vn. <P>COPYRIGHT: (C)2008,JPO&INPIT |
