What is a Variable Frequency Drive?

About 25% of the world’s electrical energy is used by electrical motors in industrial applications. This is a significant and costly power input that businesses generally look to reduce any way they can.

Variable frequency drive (VFD) systems can dramatically reduce industrial electrical consumption, while offering a range of other benefits.

A VFD is a control system that is used to drive an electric motor. It varies the frequency and voltage of the motor’s power supply, thereby adjusting the speed to better fulfill the requirements of the driven load. Since frequency is directly related to motor speed, varying the frequency will create a proportional change in the motor speed. As a result, a VFD can also be known as a variable speed drive.

Common uses

VFDs are used in applications ranging from small appliances to large industrial compressors, fans and pumps. They are regularly required for heating, ventilation and air conditioning (HVAC) systems, as well as fluid pumping systems in mining, water treatment, manufacturing, power generation and a range of other industries. They can be used to provide control systems for positive displacement pumps, gear pumps, reciprocating pumps, conveyors, extruders, extruder knife-cutters, mixers, reciprocating compressors, cooling fans, airflow systems and much more.

Reasons to implement a VFD system

There are plenty of reasons why you may want to implement a VFD systems including:

  • System efficiency and energy conservation
  • Match speed, torque or power to process requirements
  • Reduce noise and vibration and improve working conditions
  • Reduce wear and tear
  • Improve variability and flexibility of motor usage
  • Ramp up or down of motor during start up/shut down
  • Increase or reduce output during peak or off-peak periods
  • Reduce current drawn during peak demand periods

These are some of the main benefits that a VFD system can provide for electrical motors in industrial applications.

  • Reduce energy consumption and power costs

A VFD control can vary the power supply to match the requirements of the motor. Running the motor at the optimal speed helps to reduce energy consumption and electricity costs. The power required to run a motor varies approximately with the cube of the speed. This means that even a small reduction in motor speed will result in large reduction in power consumption. A VFD controlled motor will consume only 25% as much energy at 50% speed as it will at 100% speed.

While VFD systems have a fairly high up-front cost for installation, the reduction of energy costs following the installation is enough to offset, if not completely pay for, the high implementation costs.

  • Reduce carbon footprint

Reducing energy consumption has the flow-on effect of reducing the carbon footprint of machinery and processes involved. That means less carbon emissions from your processes, which is good for the planet and good for your company’s green credentials.

  • Reduce machinery wear and tear

By varying the power input of the motor, and therefore the speed, you’re minimising operational strain. This reduces wear and tear, increases the operational life of the motor, lowers repair and maintenance requirements and reduces machinery downtime.

A VFD can also be used to gradually speed the motor up and down prior to turning the motor on and off. This reduces shock damage and long-term excessive wear on the motor. At the point of energisation, a fixed speed motor at zero speed is subject to extremely high torque and can require up to 600% of full-load running current. This current will gradually drop off as the motor comes up to speed. However, this can cause serious voltage sag on the system on the power system. A VFD will help to prevent this.

  • Tighter process controls

A VFD system can provide precise control over acceleration, flow, monitoring, pressure, speed, temperature, tension, and torque. By setting electrical motors to their optimal operating parameters, you have better process control and improved precision and process sensitivity. Adjusting motor speeds can also help reduce mistakes and achieve steady motor speeds, which can be vital for machinery like conveyor belts or bottling lines.

A variable frequency drive (or variable speed drive) is a sophisticated piece of electronic engineering designed to reduce power consumption and improve the operation of electrical motors. If your systems are operating without VFD controls, it’s worth considering implementing this system today.

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