Control Engineering offers an hour of webcast instruction with practical advice on “Motors, drives: How to better manage energy with variable speed drives” on Dec. 11, and this article offers related advice on money-saving VFD installations.
Industrial controller selection insights
- Explore industrial energy saving variable speed drive advice from system integrators experts, also instructors in a December Control Engineering webcast.
- Understand how variable speed drives save energy and learn where an industrial variable speed drive can save energy.
- See the webcast for more advice: Register for the Control Engineering webcast, “Motors, drives: How to better manage energy with variable speed drives,” archived until Dec. 11, 2026.
Get advice on “Motors, drives: How to better manage energy with variable speed drives” from Control Engineering in a Dec. 11 webcast (archived for a year); webcast instructors provide controller selection advice below. The instructors (Figure 1) are:
- Mike Daugird, director, facility design and engineering, ACS,
- Roger Manrique, automation specialist, GreyLogix Brazil,
Moderator for the webcast is Mark T. Hoske, editor-in-chief, Control Engineering.
Advice on industrial energy saving drives
Variable speed drives (VSDs) [also called variable frequency drives (VFDs), inverters or just “drives”] control and optimize motor starting, acceleration, deceleration and stopping to provide energy efficiency and sustainability benefits across myriad facilities and industrial applications. When should VFDs be applied to motor applications for better energy management and why? What VFD capabilities and functions are available, used and needed to optimize energy management? How can VFDs optimize an energy management plan for the combined motor, drive and motion control systems and process applications?
Learning objectives for the webcast are to:
- Identify variable frequency drive (VFD) features, functions and applications for improved energy management.
- Assess VFD energy management and the questions to ask to improve selection, integration, application and use through the VFD and motor-drive lifecycle.
- Understand VFD application examples demonstrating quantified energy savings for smarter energy management.
How do variable speed drives save energy?
Key VFD features for energy efficiency, Manrique said, are:
- Variable torque loads (pumps/fans) via Affinity Laws and pump/fan smart algorithms.
- Constant torque loads (conveyors/compressors) using flux optimization, energy-saving modes and advanced vector control.
- System-level efficiency features such as regenerative braking and harmonic mitigation.
Daugird suggested questions to ask in four areas to identify high-potential applications. These are:
- Load type: Is it a fan or pump (variable torque loads)? These yield the highest savings
- Existing control: Is flow/pressure controlled by throttling valves or dampers? This wastes significant energy.
- Operation profile: How frequently does the system run below full speed?
- Motor compatibility: Is the existing motor VFD-rated (inverter duty) for reliable long-term use?
Daugird provided a graph that shows how VFDs vary speed to operate fans and pumps closest to the systems BEP (best efficiency point). See Figure 2. The system curve, pump curve and motor efficiency are all represented together. Operating at the BEP also increases life of a pump. Varying speed with VFDs minimizes or eliminate waste gates or control valves to short cut system loops, he said.
Engineering design considerations also can add efficiencies, Daugird said, by sizing a system to use two smaller, efficient pumps to handle day-to-day pumping. Motors typically are most efficient near 75% of rated load. Department of Energy (DOE) suggests if a motor operates for extended periods under 50%, then HP load modifications should be considered. VFDs allow “lead-lag for day-to-day demand but allow control of two pumps simultaneously for meeting peak demand to efficiently service the complete engineering performance envelope,” Daugird said.
How much savings from variable speed drives?
An example from Manrique illustrates how powerful VFDs can be when applied to pumping systems operating with throttling control.
“A 75-kilowatt pump that was originally controlled using a throttling valve — a very common setup in water utilities, industrial processes and heating, venting and air conditioning (HVAC) systems. The pump operates about 8,000 hours per year, and the process typically requires around 80% of the nominal flow. Instead of adjusting speed, the system forces the pump to run at full speed and dissipates excess energy through the valve.
“After installing a VFD, we can reduce the pump speed from 60 Hertz down to 48 Hertz, which corresponds exactly to the 20% reduction in required flow. Thanks to the Affinity Laws, we know that pump power scales with the cube of the speed. So when we go to 80% speed, the power requirement becomes 0.8 cubed — about 51% of the original.
“That means the pump now requires only about 38.4 kilowatts instead of the full 75. In other words, we save 36.6 kilowatts every hour the pump is running.
“When we multiply that by the 8,000 hours of operation per year, the total annual energy savings amount to approximately 292,800 (two hundred ninety-two thousand eight hundred) kilowatt-hours. Since the original annual consumption was 600,000 kilowatt-hours, this represents a 48.8% reduction — almost half of the energy consumed previously. By saving this much energy per year, this single pump reduces annual CO₂ emissions by approximately 80.5 tons of CO₂ in Europe, 117 of CO₂ tons in the United States, or 29 tons of CO₂ in Brazil, depending on the local electrical grid’s carbon intensity. (These CO₂ figures are approximate; use local grid factors for precise reporting.)
And this result comes from a single pump. This example clearly demonstrates how replacing throttling control with speed control directly converts wasted energy into measurable savings, and why VFD retrofits in partial-load pumping systems are among the most cost-effective efficiency improvements available.”
The Dec. 11 webcast provides additional VFD savings opportunities and examples.
Mark T. Hoske is editor-in-chief, Control Engineering, WTWH Media, [email protected].
Keywords
Industrial energy savings, variable speed drives (VSDs), variable frequency drives (VFDs)
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Register for the Control Engineering webcast, “Motors, drives: How to better manage energy with variable speed drives,” archived until Dec. 11, 2026.
