A variable frequency drive is a speed manage technique utilised for regulating the speed of an alternating present electric motor. The speed regulation is effected by varying the frequency of the electrical energy supplied to the motor. Variable frequency drives uncover wide application in ventilation systems for large buildings, conveyors, pumps, elevator, machine tool drives, and so on.

An alternating present induction motor draws up to 6 occasions its rated current at the time of start off up. The existing continues to remain high till the motor approaches the full speed. When a variable frequency drive is used to begin the induction motor, a low frequency as well as a low voltage are applied to the motor. Normally, the start-up frequency is two Hz or much less. As the frequency is low, the present flow in the time of beginning will also be low. When the motor is started employing the variable frequency drive, the applied voltage and frequency are increased at a controlled rate to make sure that the motor doesn’t draw excessive existing. This approach of starting enables the motor to as much as 150% of its rated torque at less than 50% of its rated present consumption.

The variable frequency drive technique consists of an AC motor, a controller and an operator interface. A controller is actually a solid state electronic energy conversion device. AC input energy is converted to DC intermediate power making use of a three-phase bridge rectifier program. The DC energy is then converted to quasi-sinusoidal AC energy employing an inverter switching circuit.

The advantages of a variable frequency drive are the following:

Saving in electrical power consumption is by far the most important benefit of utilizing variable frequency drives. By way of example, AC motors employed in ventilation systems are not needed to often run at peak load. Variable frequency drives save power by controlling the volume of air required for a certain program demand.

An induction motor making use of a variable frequency drive will last longer. The upkeep costs will also be lower. While classic starters commence the motors abruptly, variable frequency drives gradually boost the speed to operating speed. This contributes to a reduction mechanical and electrical pressure on the motor.

A variable frequency drive enables far better process manage. This really is since variable frequency drives could be programmed to run the motor in the necessary load, quit as per requirement and apply a specified amount of torque.

There are three types of variable frequency drives. These are continuous voltage, constant existing and cycloconverters. The most crucial section of a variable frequency drive may be the inverter circuit. These units support increase power factor and decrease harmonic distortion.