Why do 50 Hz transformers cost more than 60 Hz transformers?

The “Ask Control Engineering” blog recently received the following question from a reader: Most of the projects our company builds are used in North America, but we sometimes have to adapt equipment for overseas applications. Why is it that transformers capable of operating in a 50 Hz environment cost more than those for domestic 60 Hz operation? Is this a marketing ploy or is there...

05/01/2009


The “Ask Control Engineering” blog recently received the following question from a reader: Most of the projects our company builds are used in North America, but we sometimes have to adapt equipment for overseas applications. Why is it that transformers capable of operating in a 50 Hz environment cost more than those for domestic 60 Hz operation? Is this a marketing ploy or is there a real justification for the cost difference?

According to Steven Ensign of Ensign PowerVolt, a producer of transformers and power supplies: Back in high school physics class we observed the circular patterns, called magnetic flux lines, made by sprinkling iron filings over a magnet. An energized transformer is an electromagnet and therefore creates similar magnetic flux line patterns.

When dealing with flux lines and transformers, two laws of physics are particularly significant:

1) Each magnetic material has a limit on how many flux lines it can handle; and

2) The lower the operating frequency, the more flux lines that are generated.

Operating a transformer at 50 Hz generates 20% more flux lines than at 60 Hz. As the number of flux lines approaches the magnetic material’s limit, the heat in both the magnetic core and the internal coil wires increases, and under certain circumstances, unpredictably so. This can result in a transformer that exceeds safe temperature levels. Therefore, a transformer designed to run at 50 Hz will simply run cooler at 60 Hz. But one designed only for 60 Hz may overheat at 50 Hz.

In order to accommodate 50Hz operation, the transformer must employ a magnetic core material that can handle the added flux lines. Such materials are readily available, but they are significantly more costly than the normal core materials. Using high-grade core materials when they are not required results in transformers that are over-designed and not competitively priced.

To see more “Ask Control Engineering” questions and answers, or to post your own question, go to www.control-eng.com , click on the “Blogs” tab in the multimedia box at the right side of the page, select “View all Blogs” at the bottom of the Blogs window and scroll down to the “Ask Control Engineering” blog.





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