Using Variable Frequency Drives to Save Energy

As energy prices continue to rise, the need for energy-efficient motor control solutions grows with them. In order to reduce energy-related losses, process engineers are often turning to variable frequency drives as an alternative to throttling devices like valves and dampers, or fixed speed controllers. Today, advancements in drive technology, alongside the intelligent use of motor control strategies, and power system configurations ensure that control capacity, operating performance, and energy usage all benefit from the use of  variable frequency drives.


Of course, saving energy isn’t just beneficial for business reasons – energy efficiency also plays one of the most crucial roles in reducing CO2 emissions – responsible for as much as 53% of all CO2 emission reductions. With variable frequency drives, energy consumption cost falls by up to 60%.

The Need for Variable Frequency Drives

According to reports, the global market for variable frequency drives was worth approximately $15,489 million in 2013, and is on its way to reaching a total value of $24,703.4 million. Between 2014 and 2020, experts forecast that the market will expand at around 7%, and the growing need for a more effective way to manage energy consumption is likely to influence demand. What’s more – as various applications begin to utilize induction motors, the variable frequency drive market becomes more necessary in today’s society.

Today, variable frequency drives find purpose in the development of infrastructure, manufacturing, automotive industries, chemical processing plants, power generation, and oil and gas industries. Though the manufacturing share held the majority of the global VFD market during 2013, it’s safe to say that there is plenty of space for need to grow.

How Variable Frequency Drives Save Energy

The formula for electrical power looks like this:

Power (P) = √3 x Voltage (V) x Current (I) x Power Factor (PF)

Centrifugal loads may offer the most significant potential for energy savings using variable frequency drives to control speed. The reason for this is that energy consumption in pump applications and centrifugal fans follow the laws of affinity – meaning that flow is proportional to speed, horsepower is proportional to the cube of speed, and pressure is proportional to the square of speed. In simple terms, this could mean that if an application needs around 80% flow, the pump or fan runs at 80% speed, requiring 50% rated power.

By controlling the speed of a pump or motor, rather than controlling the flow of energy through the use of throttling valves, the amount of energy saved using variable frequency drives can be substantial – for instance, a reduction in speed of 20% can create energy savings of 50%.

The Benefit of Variable Frequency Drives

When comparing the input of a VFD to output, it’s crucial to keep in mind the variables that relate to electrical power, including:

  • Power factor
  • Current
  • Voltage

This is also significant when using the torque and speed of the motor’s mechanical power to determine the input current to the VFD. Often, with all variables in mind, the input current is impressively lower than the output current, due to power factor improvement. Note that this power factor improvement, while making the power distribution conductors more efficient and releasing distribution transformer capacity, has very little if any effect on power consumption by the process being controlled from the variable frequency drive. A variable frequency drive matches the amount of energy your motor needs with the amount of work being done – for the best possible energy savings.

How do you feel about the introduction of variable frequency drives? Do you think that they will continue to get more impressive as technology evolves?

Using Variable Frequency Drives to Save Energy was last modified: July 20th, 2017 by admin

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Jerry is the owner of Sloan Electromechanical and is active in all aspects of the company. He is passionate about doing the work RIGHT and proposing the best product solution, hence the Sloan team is focused on aligning company values with client values. Please post your questions or comments and Jerry will respond. For a faster or confidential response, please contact Jerry directly 619-515-9691 or LinkedIn
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