Variable Frequency Drives Will Take Us to Mars
A variable frequency drive can be a speed control method used 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 discover wide application in ventilation systems for big buildings, conveyors, pumps, elevator, machine tool drives, etc.
An alternating current induction motor draws up to 6 occasions its rated current in the time of begin up. The current 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 along with a low voltage are applied to the motor. Generally, the start-up frequency is two Hz or less. As the frequency is low, the existing flow in the time of beginning will also be low. Once the motor is started utilizing the variable frequency drive, the applied voltage and frequency are elevated at a controlled rate to ensure that the motor will not draw excessive existing. This technique of starting enables the motor to as significantly 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 actually a solid state electronic power conversion device. AC input energy is converted to DC intermediate power employing a three-phase bridge rectifier system. The DC power is then converted to quasi-sinusoidal AC power making use of 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 critical benefit of making use of variable frequency drives. For example, AC motors employed in ventilation systems aren’t necessary to often run at peak load. Variable frequency drives save power by controlling the volume of air required for a specific system demand.
An induction motor employing a variable frequency drive will last longer. The maintenance expenses will also be lower. Whilst classic starters begin the motors abruptly, variable frequency drives gradually improve the speed to operating speed. This contributes to a reduction mechanical and electrical pressure on the motor.
A variable frequency drive enables much better procedure manage. This is because variable frequency drives might be programmed to run the motor in the needed load, quit as per requirement and apply a specified quantity of torque.
You will find three sorts of variable frequency drives. These are constant voltage, constant current and cycloconverters. Essentially the most important section of a variable frequency drive is the inverter circuit. These units assist enhance power factor and minimize harmonic distortion.