| 摘要 |
In a method for driving an asynchronous motor with speed control by means of a controlled inverter, the desired value of the phase difference between the motor voltage and the motor current is determined as a function of the frequency of the voltage supplied by the inverter. The amplitude of the voltage supplied by the inverter is controlled to make the actual value of the said phase difference equal to the desired value at the frequency at issue. The desired value function is determined on the basis of the desired value given for the individual motor at nominal frequency and by means of the equivalent diagram of the motor. A device for carrying the method into effect comprises a detector (7) for determining the actual value of the phase difference between the motor voltage and the motor current, a comparator (8) for determining the difference between said actual value and a desired value of said phase difference, said desired value being a function of the frequency of the voltage supplied by the inverter, and a control unit (10) actuated by the difference between said actual value and said desired value, for controlling the amplitude of the alternating voltage supplied by the inverter toward equality between said actual value and said desired value at the frequency at issue. |
