Importance

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Abstract

A motor control method is disclosed in which a drive motor is connected to an adjustable frequency power supply in which the frequency of the power supplied to the motor can be selectively varied. While the motor is running at a constant speed as determined by the frequency of the power supplied to the motor, the value of the current being supplied to the motor by the power supply is sensed and an actual current signal representative of said actual current value is produced. A reference current signal which is representative of a selected maximum current value and thereby a maximum load at which the motor speed may be increased is also provided. The actual current signal is compared with the reference current signal and if the former is less than or equal to the latter, an output signal is provided. In response to the output signal resulting from the comparison, the value of the actual frequency of the power supplied to the motor is increased to a preselected value so that the motor speed also increases. The acceleration rate of the motor while its speed is increasing may also be changed.

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First Claim