Browsing by Author "ASADULLAH NASIR"

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    Variable frequency drive to control ac motor speed and torque using inverter
    (UMT.Lahore, 2013) ASADULLAH NASIR; RIZWAN QAYYUM; WAQAS MAHMOOD
    AC motor drives are widely used to control the speed of conveyor systems, blower speeds, pump speeds, machine tool speeds, and other applications that require variable speed with variable torque. Our varying industrial needs demand more precise control of the outputs of our basic electrical prime movers i.e, THE MOTORS. Basically dc motors are easy to control compared to their ac counter parts, but they have their own limitations with increase in capacity. Conversely ac motors in particular squirrel cage induction motors are very economical but their speed control is comparatively difficult because it requires alteration of supply frequencies.Due to technological advancements some drives which can control ac motors are available which are economical, easy to use and which can provide wide range of speed control both below and above base speeds.These drives fundamentally alter the voltage and frequency being fed to motor according to the requirements using a technique called pulse width modulation (PWM).These are increasingly becoming popular due their reasonable cost and other user friendly features. Since they use embedded systems they can be interfaced to the computers and can be programmed for automatic control reducing manual intervention.A variable voltage variable-frequency drive (VVVFD) is a system for controlling the rotational speed of an alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor. A variable frequency drive is a specific type of adjustable-speed drive. Variable-frequency drives are also known as adjustable-frequency drives (AFD), variable-speed drives (VSD), AC drives or inverter drives.