| 摘要 |
PURPOSE:To stabilize no-load rotational speed by setting a no-load limit current at a level slightly higher than the no-load current during lead angle control and setting a predetermined lead angle so that a same rotational speed is obtained when the no-load current during lead angle control is lower than the limit no-load current. CONSTITUTION:When no-load current is larger than a limit no-load current which is slightly larger than the no-load current during lead angle control, a lag angle phi1 is determined through lead angle control and a corresponding lead angle lambda is calculated. An effective value calculating section 6 determines the effective value of U-phase current for every 2pi section while a dead band check section 8 compares the effective value of U-phase current with a limit no-load speed. When the U-phase current is lower than the no-load limit current, a switch 11 is switched and a constant lead angle lambda is inputted regardless of the output value lambda from a PI control section 9. |
