Why and How to Vary Speed in an Industrial Centrifugal Fan

A variable-speed fan is just what it sounds like. In this case, we’re talking about an industrial centrifugal fan that is capable of operating at more than one speed. That means it can run above or below the constant motor speed specified. There are several reasons why you would need a variable-speed fan, several ways to do it, and a few things to be careful to avoid when operating at varied speeds.

What Drives the Need for a Variable-Speed Fan?

A variable-speed fan adds efficiency and performance by reducing energy consumption compared to fixed-speed fans in an industrial setting. They enable adjustments to speed based on the demand, saving energy during periods of lower airflow requirements. Lower energy consumption also means lower energy costs. Some industrial applications also require variable speed fans to achieve specific airflow rates or patterns to meet the process requirements, enhancing productivity and quality.

Ways to Vary Centrifugal Fan Speed

The ability to control fan speed for optimal efficiency, performance, and productivity depends on the motor drive. On direct-driven fan applications, we tend to use a variable frequency drive (VFD) for external control of the fan’s motor.

A VFD can also be effective on belt-driven fan applications for simple speed changes. However, one of the benefits of a belt drive is that it enables the fan’s operating speed to differ from the motor’s synchronous speed. You can accomplish this by modifying the sheave ratio on the belts.

What to Watch Out For

Even when a variable-speed fan is optimal, there are still some precautions to keep in mind. Every industrial fan has a max design speed, and you need to avoid speeds that are either higher than that.

Each application is unique, and you may find that certain speeds excite a natural frequency within the fan and cause it to run at a higher vibration. Vibration can cause a host of other issues like excess noise, fan imbalance, and ultimately bearing failure. You’ll need to know and avoid those speeds as well.

Hear from an Application Engineer About the Variable Speed Fan

Chet White, Senior Application Engineer / Sales & Marketing Manager, illustrates the variable speed fan in this 1-minute whiteboard video.

To ask questions, get more details, or discuss your application, reach out and connect with one of our application engineers.

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