Nov 11
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A variable frequency drive can be a speed control method 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 find wide application in ventilation systems for significant buildings, conveyors, pumps, elevator, machine tool drives, etc.
An alternating existing induction motor draws as much as 6 occasions its rated current at the time of begin up. The present continues to stay high till the motor approaches the full speed. When a variable frequency drive is utilized to begin the induction motor, a low frequency and a low voltage are applied to the motor. Normally, the start-up frequency is 2 Hz or much less. As the frequency is low, the existing flow in the time of starting will also be low. Once the motor is started using 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 existing. This method of starting enables the motor to as considerably as 150% of its rated torque at less than 50% of its rated current consumption.
The variable frequency drive system consists of an AC motor, a controller and an operator interface. A controller is actually a solid state electronic energy conversion device. AC input power is converted to DC intermediate power using a three-phase bridge rectifier method. The DC energy is then converted to quasi-sinusoidal AC power employing an inverter switching circuit.
The benefits of a variable frequency drive are the following:
Saving in electrical energy consumption is by far the most critical benefit of making use of variable frequency drives. As an example, AC motors employed in ventilation systems are not necessary to constantly run at peak load. Variable frequency drives save power by controlling the volume of air necessary for a certain method demand.
An induction motor utilizing a variable frequency drive will last longer. The maintenance costs will also be lower. Although traditional starters begin the motors abruptly, variable frequency drives gradually enhance the speed to operating speed. This contributes to a reduction mechanical and electrical tension on the motor.
A variable frequency drive enables much better approach manage. This really is because variable frequency drives can be programmed to run the motor at the needed load, cease as per requirement and apply a specified amount of torque.
You’ll find 3 types of variable frequency drives. These are constant voltage, continuous existing and cycloconverters. Essentially the most important section of a variable frequency drive could be the inverter circuit. These units assist improve power factor and minimize harmonic distortion.
