| 摘要 |
PURPOSE: To improve accuracy in slip compensation by calculating, at a higher constant frequency, a compensation value that is added to the rotary speed of a motor when it is driven at a lower approaching frequency. CONSTITUTION: A pulse width modulator 5 supplies an electrical stator frequency fs to an inverter 1 as a frequency command. A slip compensation circuit 6 is added to compensate for slipping. The slide compensation circuit 6 calculates a correction term kT at 50% of the rated frequency of the motor and stores it in memory. Then, when the correction term kT becomes necessary at a frequency being at 20% or less of the rated frequency of the motor, the value of the correction term kT which is stored is added to an adder 7. In this manner, by calculating at a higher constant frequency, a compensation value added to the rotary speed of the motor being driven at a lower approaching frequency, the effects of scattered power on the calculation accuracy of the value can be eliminated, thus improving the accuracy in the slide compensation. |
