Power Transformers Blog – Expert Safety and Usage Info

MIDWEST replaced the old main electrical power transformers for a manufacturing facility.  When we were done, the outdoor substation looked barren. It looked like the power capacity went way down.  We removed one 1000 kva oil filled three phase Westinghouse transformer, one 1000 kva oil filled three phase GE General Electric Transformer, and three 167 kva single phase oil filled transformers. We replaced all these transformers with one new oil filled 3750 Kva transformer. We replaced the concrete pad, of one of the old 1000 kva transformers, with a larger pad. Installed a new grounding system and replaced the fencing. But the new installation made the substation look bare.  Where there were five old oil filled transformers, there was now one new oil filled power transformer. The new 3750 kva transformer wasn’t much larger than one of the old scrap 1000 kva transformers. But, when you looked at the substation, you saw four abandoned concrete pedestals for the removed transformers. And that made the place look like it was going out of business, rather than growing.

The size of many very old GE General Electric, Westinghouse, and especially Allis Chalmers oil filled electrical power transformers was a third to even 100% larger than a new same Kva power transformer. Pad mount transformers are especially smaller because of their low profile.  The low profile green box pad mount transformers got extensive early use in subdivision developments, where the new owners of dream homes didn’t want ugly electrical overhead lines and transformers outside their windows. The little green boxes were small and everywhere, but there were barely noticeable because of their size and color.

So, for electrical power transformers, new is less, less space that is.  

MIDWEST frequently replaces old oil filled transformers with more efficient new oil filled power transformers. Being a specialty engineering firm, we usually get involved when the project is messy. We had a recent project involving replacement of very old Allis Chalmers 600 kva and 1000 kva oil filled conservator tank transformers.  These were monster units compared to the size the replacement transformers, which were 1000 kva.  As a training exercise, MIDWEST had a shop crew tear one of the old transformers apart. They quickly found out that the bushings for the old transformers extended twice as far inside the tank as they did outside. These may have been obsolete transformers, but they were built like battleships and who knows how long they may have lasted. The crew got a good look at the workings of the conservator tank.  Then they removed the top. The old transformer had a bolted on top and the core and coil assembly was bolted to the top, such that the transformer core and coil came out of the tank when the top was lifted. The crew was surprised at how small the core and coil assembly was. They thought it probably took up only the bottom third of the tank. We know that new replacement transformers are much smaller and lighter than the old and obsolete transformers used for manufacturing plants across the country. When we do a power transformer replacement, we seldom have to worry about space when the transformer being replaced is 60 years old.  Actually we have to provide a raised concrete pedestal when installing a new oil filled power transformer in place of one of these old units. So, as strange as it may be in this case, for a replacement electrical power transformer, new is small and old is tall. And seeing is believing.