A method and apparatus for computing moment of inertia in a motor speed controller, and a speed control method and apparatus for motor.

摘要

In a motor speed controller for controlling an AC motor (6) to be driven at a variable speed, a signal proportional to a load torque and a signal proportional to an output torque of the AC motor are found by current detecting means (5) for detecting the primary current of the AC motor, and integrated over the speed changing period, and the integrated values are divided by the values corresponding to the amounts of speed change during the speed changing period so that the moment of inertia can be computed. In addition, there is provided means (8) for changing the rate of output frequency change caused by the output frequency command into a value according to the calculated moment of inertia. Moreover, there is provided a circuit for detecting a sudden change of the calculated moment of inertia, so that when a sudden change occurs, an abnormality signal is generated.