A variable frequency drive can be a speed manage system utilised for regulating the speed of an alternating existing electric motor. The speed regulation is effected by varying the frequency of the electrical energy supplied towards the motor. Variable frequency drives uncover wide application in ventilation systems for huge buildings, conveyors, pumps, elevator, machine tool drives, et cetera.
An alternating current induction motor draws up to 6 times its rated present at the time of start off up. The existing continues to stay high till the motor approaches the full speed. When a variable frequency drive is utilized to start the induction motor, a low frequency plus a low voltage are applied towards the motor. Normally, the start-up frequency is 2 Hz or much less. Because the frequency is low, the current flow in the time of beginning will also be low. Once the motor is began utilizing the variable frequency drive, the applied voltage and frequency are elevated at a controlled rate to make sure that the motor doesn’t draw excessive present. This technique of beginning enables the motor to as significantly as 150% of its rated torque at less than 50% of its rated current consumption.
The variable frequency drive technique consists of an AC motor, a controller and an operator interface. A controller is really a solid state electronic energy conversion device. AC input power is converted to DC intermediate energy making use of a three-phase bridge rectifier system. The DC power is then converted to quasi-sinusoidal AC power using an inverter switching circuit.
The advantages of a variable frequency drive are the following:
~ Saving in electrical power consumption is by far one of the most crucial benefit of making use of variable frequency drives. For example, AC motors utilised in ventilation systems are not needed to constantly run at peak load. Variable frequency drives save power by controlling the volume of air required for a specific program demand.
~An induction motor making use of a variable frequency drive will last longer. The maintenance expenses will also be lower. While classic starters start the motors abruptly, variable frequency drives gradually improve the speed to operating speed. This contributes to a reduction mechanical and electrical anxiety on the motor.
~A variable frequency drive enables much better process manage. This really is due to the fact variable frequency drives might be programmed to run the motor at the necessary load, stop as per requirement and apply a specified amount of torque.
You can find 3 types of variable frequency drives. These are constant voltage, constant current and cycloconverters. Probably the most crucial section of a variable frequency drive is the inverter circuit. These units assist increase energy element and decrease harmonic distortion.
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