| 摘要 |
PURPOSE:To prevent a stall at the time of passing the secondary resonance point by setting the switching point of acceleration range within the range of the number of rotations generating the secondary and tertiary resonance points of a load. CONSTITUTION:A rectification section converting alternating current into direct current and an inverter section inverting the converted direct current into any AC frequency are provided. The frequency f linearly increases from start to the maximum number of rotations. Meanwhile, the terminal voltage V raises by nearly fixing v/f at the accelerating range Na and then only the frequency f raises by fixing the primary constant voltge Vc1. Then, the voltage Vc1 raises in stepped shape and only the frequency f raises by fixing the secondary constant voltage Vc3. At that time, the primary constant voltage setting point C1 is set at the range of the number of rotations higher than the number of load rotations Nv2 generating the secondary resonance V2. In this way, sufficiently large margins can be secured as compared with the case when the setting point is set at C' point (P point at curve Tm') located between the load requiring torque curve Tw and driving motor torque curve Tm at the number of load rotation Nv2. |
