Power Transformers Blog – Expert Safety and Usage Info

At MIDWESTwe often get calls or receive inquiries from individuals or company employees seeking an exact transformer replacement for a particular unit.  The reasons are numerous.  Their existing transformer failed suddenly or they have a transformer that is in the process of failing.  Maybe they are trying to expand their facility with limited funds and do not want to pay for the services of an engineering consultant.  They look around and decide to copy what they already have and reason if they just had another one just like it and moved the walls out a bit, their newly purchased used machine ( another blog at another time) which hopefully will mean more income.  Possibly the building has a new owner and they are looking for a spare transformer (a gold star to them for being pro-active).  ‘Finding another one just like it’ is easy if you are shopping for a jar of Jiff ® or Skippy®.  But looking for running shoes just like the kind you purchased last year can be difficult.  Now you can imagine just how difficult it is to locate an identical twin to transformer in a building over thirty years old, assuming the transformer nameplate exists, is still legible and not covered with paint.  If you are fortunate to have the model or type number, a Google search may yield a possible match. Hopefully it is an available unit for sale and not a line item on a specification for a future construction project.

A GOOGLE search with only the transformer brand will help you find a soulmate who is usually looking for product data or a wiring diagram for that brand of transformer. 

Sadly, some transformer companies are no longer in business, their assets were sold to another company, the factory shuttered and you trail runs cold.

Assuming the transformer was not built for an Arc furnace and is a one-of-a kind relic (see future blog) you can usually replace a transformer that was made by company X with a transformer that was manufactured by Company Y.  To do so requires a complete list of specifications with all available information on the transformer whether you think it is relevant or not.  There are a lot of parameters that need to be known: KVA, footprint, height and weight, impedance and most importantly the primary and secondary voltage and also if this is a single phase or three phase transformer.  You also need to know where the transformer will be used (outdoors, indoors).  If it is a fluid filled unit, what type of fluid?  If it is a dry transformer (conventional dry type or encapsulated).  You have to know if this transformer needs to have high side voltage taps and if the primary and secondary are Delta or Wye.  If it is a large power transformer, where are the bushings and how are they arranged. Doing your homework first before you have the transformer shipped to you from another state will help you avoid the embarrassment, grief and additional charges that will rack up if the replacement transformer arrives and it will not fit or is suitable for the application or you discover your cable stretcher is undersized.

by Vince

We like it when we run into something unusual.  Recently we had a request for a replacement transformer.  That wasn’t unusual until they told us they wanted a pad mount dry type transformer. That was a surprise. He was surprised we had one.  The company may have been trying to go green and was under a mandate to no longer use fluid filled transformers. This is becoming more common.  We see quite a few companies that require all replacement transformers to be dry type because of their “Green” policy.  Fortunately most of these companies are commercial facilities and do not use higher voltages and do not have huge loads. In addition, the transformers for commercial facilities are often indoors where dry type transformers are appropriate. Therefore non fluid filled replacement transformers are available and “Going Green” is a good option.  But an outdoor dry type pad mount transformer is uncommon.  Most pad mount transformers are oil filled.  And most pad mount transformers are green, painted green.  Pad mount transformers were developed decades ago for use in subdivision developments.  They were replacements for overhead distribution transformers.  The under ground distribution systems and low profile green box shaped transformers were unobtrusive in the beautiful new subdivisions.  So suburbia went green decades before it became environmentally important, but they did it for cosmetic reasons.

But that is not true for industrial facilities that frequently have higher voltages and larger loads, for example over 25 kv and over 3750 kva.  MIDWEST did have one occasion where a manufacturing plant wanted to eliminate the fire hazard of fluid filled transformers. But it was only because their insurance carrier determined their transformers were so close to the outside building walls that they created a fire hazard.  They were not trying to go green, they were trying to avoid going black.  Dry type replacement transformers would not reasonably work because of the size of their transformers.