| 摘要 |
The invention is carried out by providing an adjustable frequency power supply connected to an alternating current induction motor which is rotated at speeds in excess of 60 hertz. A plurality of sequential frequency ranges are selected which, together, comprise a total frequency range from a maximum frequency range in excess of 60 hertz to 60 hertz which is applied to the motor. For each frequency range, a maximum breakdown torque of the motor is determined. When it is desired to decrease the speed of the motor, it is decelerated sequentially through each frequency range at a different deceleration rate for each range such that the maximum breakdown torque of the motor within each frequency range is not exceeded. Each different deceleration rate for each frequency range is determined by selecting the minimum period of time, for each frequency range, during which the motor may be decelerated without exceeding the maximum breakdown torque of the motor within that frequency range. Also, the deceleration rate for each frequency range may be selected by determining the deceleration rate of the motor at the highest frequency in each range which will not result in exceeding of the maximum breakdown torque of the motor. The motor is then decelerated within each range at the deceleration rate of the highest frequency in the range. |
