FAQs Archive | JDM Air Power Services Inc.

Q: Why Does My VFD Controlled Fan Run Rough at Certain Speeds?

When using a Variable Frequency Drive (VFD) to control fan speed, you may notice that the fan runs rough or vibrates excessively at certain speeds. This can often be attributed to two main causes: unbalance and resonance. Unbalance: If unbalance is the primary issue, the fan will tend to run worse as speed increases. This is because the unbalance force is proportional to the square of the RPM (revolutions per minute). As the fan spins faster, any slight imbalance in the rotating components becomes magnified, causing increased vibration and rough operation. In such cases, the fan may run more smoothly at lower speeds, but the vibration will intensify as the RPM climbs. Resonance Condition: In some cases, the fan may run rough at specific speeds but smooth out again as speed continues to increase. This is a sign of a resonance condition in the system. Resonance occurs when the frequency of the fan’s rotation matches a natural frequency of the system, amplifying vibrations. As the speed moves away from this resonant frequency, the vibrations may subside. Resonance can cause significant wear and tear on the fan and related components if not addressed. To resolve this, vibration analysis can be used to identify resonance frequencies in the system. Once the resonant speeds are known, the VFD can be programmed to avoid prolonged operation at those speeds. This adjustment helps to prevent damage and ensure smooth operation across a broader range of speeds. Working with a qualified technician to diagnose and adjust for these issues is crucial to maintaining optimal performance and prolonging the lifespan of your VFD-controlled fan system.

Q: My Fan Has Been Balanced But Is Still Shaking, Why?

While unbalance is one of the most common causes of excessive vibration in rotating machinery, it’s not the only factor. Even after balancing, your fan may still shake due to other underlying issues. Vibration analysis can help pinpoint additional causes, such as: Misalignment: If the fan and motor shafts are not properly aligned, this can lead to uneven distribution of forces, causing vibrations. Mechanical Looseness: Components within the fan or surrounding machinery may be loose or worn, contributing to instability and excessive shaking. Soft Foot Condition: This occurs when one or more of the mounting points for the equipment is uneven or not properly secured, resulting in vibrations. Bearing Issues: Worn or damaged bearings can also contribute to vibrations, even if the fan has been properly balanced. A thorough vibration analysis will help identify the root cause and allow for appropriate corrective actions, ensuring smoother operation. It’s always a good idea to have a technician evaluate these potential issues as part of your maintenance plan.

The Rotating Equipment Specialists

(519) 624-2131

inquiries@jdmairpower.com

The Rotating Equipment Specialists

(519) 624-2131

inquiries@jdmairpower.com

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The Rotating Equipment Specialists

Proudly serving businesses across Ontario, Canada, and North America, providing reliable solutions for industrial fans, motors, and rotating machinery. Whether you need local support in cities like Cambridge, Guelph, Kitchener, or Waterloo, or services across the country and beyond.

JDM Air Power Systems Inc. provides expert industrial fan and rotating equipment services, including vibration analysis, predictive maintenance, and performance testing. We specialize in diagnosing and repairing complex machinery issues with over 30 years of experience in field supervision, parts replacement, and installation. Proudly serving industries across Canada, JDM offers dependable solutions for industrial fans, motors, coils, dampers, and more. Trust us for reliable, cost-effective mechanical services tailored to keep your equipment running smoothly.

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