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Why Do Transformers Hum? Understanding Transformer Noise

Why Do Transformers Hum? Understanding Transformer Noise

Loud equipment is often a nuisance, but it can also be a safety issue if it contributes to excessive noise levels. Transformers often hum or buzz, but it usually doesn’t mean anything is wrong with them. Humming can be a sign of normal operations and magnetic forces at work. Still, too much transformer noise can cause problems in workplaces and public areas, so understanding why transformers make noise can help you reduce humming and its adverse effects.

Knowing how to reduce transformer noise requires understanding several mechanical processes and the unique characteristics of your installation.

What Makes a Transformer Hum?

Magnetostriction is the main reason for transformer noise. It refers to how ferromagnetic materials expand and contract in response to magnetic fields. When the field is applied, the molecules extend. When the field is removed, they contract and return to their original shape. A transformer generates magnetic excitation with alternating voltages and currents. This magnetic activity produces flux, lines of magnetic force that run through a material — in this case, the transformer core. When you apply higher flux levels to a transformer, you get higher levels of magnetostriction and noise.

A transformer’s core comprises many magnetic sheets, which expand and contract in response to the magnetic fields generated by the transformer. They do this twice per magnetization cycle, so a transformer running at 60 cycles per second would experience 120 cycles of expansion and contraction. The latter measurement gives us the fundamental noise frequency.

These movements don’t occur uniformly. They can be erratic, which causes the transformer to emit noise in different multiples of the fundamental noise frequency. All the movements are too small to be seen with the naked eye but large enough to produce vibration and noise.

Other elements that can contribute to a transformer making noise include the following:

  • Age: As a transformer ages, the layers in the core can start to come apart and increase the noise that occurs during vibrations.
  • Fans: The more heat a transformer generates, the more fans it may need. These fans can contribute to the overall noise related to the transformer’s operation.
  • Windings: Transformer windings also expand and contract along with the current, adding noise to the system.

These are just a few of the reasons you should purchase a high-quality transformer that can minimize heat and stress and stay in good condition for decades.

How to Reduce Humming Noise in a Transformer

Although flux is related to a transformer’s vibrations, reducing noise is more complicated than reducing flux. Many different factors determine a transformer’s voltage, including the system requirements and the number of turns in the winding. Plus, the relationship between flux and magnetostriction is not linear. If you increase the magnetization, the level of magnetostriction won’t change by the same amount. Using flux to adjust noise levels isn’t economical and won’t reduce the noise very well.

Instead, you can use other tactics to reduce transformer hum. Here are some effective methods for minimizing noise.

1. Install Your Transformer in the Right Place

Consider how sound travels when placing your transformer. The ideal location is one that:
Install Your Transformer in the Right Place

  • Has minimal traffic: While keeping your transformer away from people won’t reduce its noise, it can make the sound less irritating to passersby and safer for workers. A space with low traffic can help keep the noise of the transformer away from business operations, allowing you to create a better experience for everyone, such as guests walking by an apartment building or employees who can easily communicate with each other.
  • Has a heavy, sturdy surface: Install your transformer on reinforced concrete that’s 10 times as heavy as the unit itself. This dense, heavy surface won’t amplify the noise like thin walls and plywood can.
  • Is away from corners, stairwells or corridors: Each of these areas can reflect and amplify sound waves, making the hum seem louder than it already is. Avoid these bends and other twists and turns that could create more noise reflections.
  • Has about 10 feet of clearance: Similarly, your transformer should sit a safe distance away from other equipment and objects. Distance is an affordable, simple way to reduce noise.

2. Fix Any Loose Components

As with other types of equipment, loose bolts and screws can add noisy vibrations. Make sure all of these elements are screwed in tightly to prevent noise from the transformer’s housing and incorporate them into regular maintenance procedures so they stay in place. Remember to remove any mounting screws you used.

3. Use Noise-Dampening Materials

Noise-dampening materials can be especially effective in reducing transformer hums and keeping the noise away from people working or passing by in the area. Acoustic materials generally work by trapping sound waves and dissipating the energy, effectively absorbing the sound. They can make a significant difference in how far the sound from a transformer can travel and make the surrounding area much more enjoyable.

Some products you can use include:

  • Acoustic tiles
  • Outdoor wall panels
  • Acoustic enclosures
  • Oil barriers
  • Cushion padding

4. Use a Transformer From a Quality Manufacturer

Although hum is a normal part of transformer operation, you can minimize excess noise by getting your equipment from a trustworthy company. A quality company is more likely to have well-designed equipment, such as transformers with sturdy joints and flat, consistent steel. Even something as simple as fewer bolts in the transformer can help reduce noise since the unit has fewer parts that can come loose and start rattling.

Manufacturers can also help minimize noise with good cooling technology. A cool transformer has less need for fans and other noisy parts that would keep it in optimal temperature ranges.

Keep an eye out for innovative new transformer designs, too. As manufacturers continue improving engineering and materials, soundproofing measures should benefit.

Find the Right Transformer for Your Installation

Find the Right Transformer for Your Installation

A hum is the sound of a working transformer, but the noise can still be troublesome. A good installation involves considering the effects of the hum and what resources you have available to combat it. For example, if you need to keep your transformer close to the equipment it powers, you won’t have enough room to reduce sound over a long distance.

ELSCO Transformers offers a wide range of dry type and pad-mount transformers, with many available to ship in 24-48 hours. Our transformers are made with high-quality materials to help you keep noise levels down for years to come. Our team has decades of industry expertise to help you solve sound issues, including custom-built transformers, retrofits and repairs. Whether you’re ready for a new, quieter transformer or need to fix an old one, we’re here to help. Request a quote today to get started!

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