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The speed of motors in industrial sectors is controlled in two major ways- either by controlling the frequency or voltage. Comparing the two, controlling frequency tends to give better control owing to constant flux density. This is where Variable Frequency Drives come in.
A Variable Frequency Drive (VFD) also known as variable speed drive or adjustable frequency drive, is a motor controller that works by varying the voltage and frequency of power supplied to the electric motor, thereby controlling speed and torque in in electro-mechanical drive systems.
VFDs are power conversion devices that work by converting fixed frequency of the input power and voltage power to a variable voltage and frequency output in order to control the speed of the induction motor. It consists of a high speed central controlling unit, power electronic devices, and optional sensing devices.
Electric motors in industrial applications consume more than 25% of the world’s electrical energy. This can be controlled using VFDs in centrifugal load service, which helps ensure efficiency. VFDs are used in drive systems comprising three main subsystems: drive/operator interface, and main drive controller assembly, and AC motor. VFDs come in several diverse low and medium voltage, AC-AC, and DC-AC topologies.
As the demand for better automation and energy efficient machines continue to rise, there’s a daily increase of VFD applications in different machines. VFDs are used in a wide range of equipment in the manufacturing plants, ranging from small machine tools to large-scale compressors. In places that VFDs are used, there is a high need for enhanced functionality, especially in areas with great demand for equipment that handle complex automation tasks.
A VFD works by taking power on the supply side, inverting it, storing that voltage, and using an internal technology called IGBT’S to create a sine wave-like form that can be manipulated. The converter is the first stage of the Variable Frequency Drive.
It comprises six diodes that allow the current to flow in one direction; usually, the direction indicated by the arrow in the diode symbol. For instance, when the A-phase voltage is more positive than B or C phase voltages, the diode will open and The A-phase diode closes. If the B-phase becomes more positive than A-phase, the A-phase diode will close as the B-phase diode opens.
This process is similar to the other three diodes on the negative side. This is what leads to the six current pulses given that each diode opens and closes. This is referred to as a six pulse VFD.
Other benefits of a Variable Frequency Drive in the industrial setting include:
To help enhance understanding of these drives, improve overall productivity and increase the lifespan of your VFDs, it’s important to ensure that your employees are well trained on how to properly operate and maintain them.
Your employees need to learn troubleshooting and repair of VFDs. Good training will ensure that the drives your employees work on will run safely and efficiently. If you’re interested in expanding your employees’ knowledge on VFDs, contact NTT training today to enroll them for training on Variable Frequency Drives.
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