METHOD FOR INCREASING THE SPEED OF AN ALTERNATING CURRENT MOTOR

摘要

A motor control method is disclosed in which a drivemotor is connected to an adjustable frequency power supplyin which the frequency of the power supplied to the motorcan be selectively varied. While the motor is running at aconstant speed as determined by the frequency of the powersupplied to the motor, the value of the current beingsupplied to the motor by the power supply is sensed and anactual current signal representative of said actual currentvalue is produced. A reference current signal which isrepresentative of a selected maximum current value andthereby a maximum load at which the motor speed may beincreased is also provided. The actual current signal iscompared with the reference current signal and if the formeris less than or equal to the latter, an output signal isprovided. In response to the output signal resulting fromthe comparison, the value of the actual frequency of thepower supplied to the motor is increased to a preselectedvalue so that the motor speed also increases. The accel-eration rate of the motor while its speed is increasing mayalso be changed.