How to Build Your Very Own Backyard Variable Frequency Drives
Monday, November 21st, 2011A variable frequency drive is actually a speed manage technique utilized for regulating the speed of an alternating existing electric motor. The speed regulation is effected by varying the frequency of the electrical energy supplied to the motor. Variable frequency drives find wide application in ventilation systems for big buildings, conveyors, pumps, elevator, machine tool drives, and so on.
An alternating existing induction motor draws as much as 6 times its rated present in the time of begin up. The present continues to remain high till the motor approaches the full speed. When a variable frequency drive is utilised to start the induction motor, a low frequency plus a low voltage are applied to the motor. Usually, the start-up frequency is 2 Hz or much less. As the frequency is low, the present flow in the time of beginning will also be low. As soon as the motor is began employing the variable frequency drive, the applied voltage and frequency are increased at a controlled rate to make sure that the motor will not draw excessive existing. This approach of beginning enables the motor to as much as 150% of its rated torque at much less than 50% of its rated existing consumption.
The variable frequency drive system 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 power utilizing a three-phase bridge rectifier technique. The DC energy is then converted to quasi-sinusoidal AC energy employing an inverter switching circuit.
The positive aspects of a variable frequency drive are the following:
Saving in electrical power consumption is by far one of the most essential benefit of employing variable frequency drives. By way of example, AC motors utilised in ventilation systems aren’t needed to always run at peak load. Variable frequency drives save energy by controlling the volume of air needed for a specific system demand.
An induction motor utilizing a variable frequency drive will last longer. The maintenance fees will also be lower. Even though conventional starters begin the motors abruptly, variable frequency drives gradually enhance the speed to operating speed. This contributes to a reduction mechanical and electrical anxiety on the motor.
A variable frequency drive enables greater method manage. This really is due to the fact variable frequency drives could be programmed to run the motor at the necessary load, quit as per requirement and apply a specified amount of torque.
You will find three sorts of variable frequency drives. These are constant voltage, constant present and cycloconverters. One of the most crucial section of a variable frequency drive may be the inverter circuit. These units assist enhance power factor and decrease harmonic distortion.