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What are Variable Frequency Drives and How do they Impact my Business?

12/21/2018

What are Variable Frequency Drives and How do they Impact my Business?

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.

The Use of VFDs in Industrial Settings

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.

Importance of VFDs for an Industrial Business

  • Energy Savings: Variable torque loads operated with a VFD will reduce energy consumption. Therefore, if a business has an application that doesn’t necessitate maximum speed to run, energy costs can be reduced by simply controlling the motor with a VFD. Variable Frequency Drives allow a business to perfectly match the load requirement to the speed of a motor-driven machine. Electric motor systems consume more than 60% of the power consumption in industrial plants. The utilization of the available motor control systems by either installing or upgrading to Variable Frequency Drives can help reduce energy use in your facility by 30 to 35 percent. Furthermore, the use of VFDs helps reduce production costs and improve product quality.
  • Growth in production as a result of tighter process control: With VFDs, there are usually fewer or no mistakes especially if the motors in a business are operated at the most effective speed for the application. This boosts production levels, earning a business higher revenues. On both conveyors and belts, it helps get rid of jerks on start-up which allows high throughput.
  • Controlled Acceleration: Unlike AC motors that start across the line, VFD starts at zero speed and smoothly accelerates on an adjustable ramp. This helps reduce mechanical shock for the mechanically connected load and the motor, which consequently helps reduce wear and tear. Rather than being subjected to an abrupt jerk to full power, a slow ramp-up in power allows equipment to smoothly speed up.

Other benefits of a Variable Frequency Drive in the industrial setting include:

  • Reduced power disturbances
  • Lower power demand on start
  • Adjustable torque limit
  • Controlled stopping
  • Lower maintenance costs
  • Elimination of the need for expensive mechanical drive components

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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