| 摘要 |
PURPOSE:To improve the rise of generating torque and starting characteristic, by increasing the set value of slip frequency when an induction motor is in a starting range. CONSTITUTION:A speed command value omega'm and a speed detection value omegafrom a speed detector 6 are input to a subtracter 17, and the output of its difference omegam is directed to slip frequency setting units 15a, 15b. The setting units 15a, 15b output a first and a second slip frequency omegas1, omegas2 against the difference omegam, respectively. In the meantime, by a speed comparator 14, it is discriminated whether the speed detection value omegam is equal to or less than a reference value omegams, or not, and when a device is in a starting range, then a change-over switch 16 is changed over to the slip frequency setting unit 15b, and when the device is out of the starting range, then the switch 16 is changed over to the slip frequency setting unit 15. Then, from an adder 18, the output of the added value of the slip frequency and the speed detection value omegam, as primary frequency omega' is directed to a PWM circuit 7a. |
