How does the noise level of MGM Transformers compare?

It’s not by accident that you rarely hear transformers while visiting schools, hospitals, and offices. These sound sensitive environments often call for quiet transformers, and MGM can design units with sound levels an average of 3 dB below NEMA ST-20 standards. For some KVA ratings and KV classes, we can reduce sound levels up to 7 dB below NEMA!
What Causes Transformer Noise?
Transformers, by design, produce an audible “hum” caused by vibrations in the electrical steel. The vibrations are caused by a property known as “magnetostriction” which causes the core steel to change its shape and dimension while magnetized. As the vibration increases, the ‘humming” sound levels rise.

Why is it Important to Reduce Noise Levels?
For all units, MGM adheres to NEMA standards that specify sound levels depending on KVA. Additionally, there are special applications where increased noise reduction is critical. Examples include hospitals, high-rise buildings, schools, offices, libraries or other uses where transformers are placed near their loads in noise-sensitive environments.
How Does MGM Reduce Noise Levels?
MGM has a proprietary noise-reduction design that uses techniques to minimize magnetostriction-caused humming. Our design adjusts the clamping force, core material, core design, and installs anti-vibration pads throughout the unit. In addition to design, transformer placement is critical, so MGM offers support services to ensure acoustical principles are considered during installation.
How Does MGM Test Noise Levels?
Per the NEMA testing standards, MGM tests each unit at its rated frequency & voltage under no-load conditions. The testing room is approximately 10 feet larger than the transformer on all sides with an ambient sound level of 5 db. Five sound readings are taken with an approved / calibrated sound meter one foot from each side of the transformer enclosure and one foot above the enclosure. The sound rating is the average of these five readings.