Power Transformers Blog – Expert Safety and Usage Info

MIDWEST had a customer who wanted to ask a question about a transformer but he said he was afraid we would laugh at him or think he was stupid. We assured him the only stupid questions are those not asked. He wanted to know if there was such a thing as transformer mounting feet. He had checked the internet and didn’t find anything helpful. He was told by an engineer to make sure they removed the mounting feet from a new transformer their company had bought to replace a failed transformer. He was a purchasing agent and thought the engineer was trying to embarrass him so he didn’t ask any questions. He had rented a 1500 kva electrical power transformer from MIDWEST in the past and thought we could help him. And we did. Dry type electrical power transformers have vibration dampening pads between the transformer mounting feet and the frame of the enclosure. These pads dampen the mechanical vibrations caused by the transformer. The mechanical vibrations cause sound vibrations, noise, which can be a problem. Excessive mechanical vibrations can cause a lot of trouble over time. And noise can be a huge negative human factor if people are working in the area. New transformers are shipped with mounting bolts between the transformer mounting feet and the frame of the transformer. Typically these mounting bolts go right through the vibration dampening pads. There are instructions for loosening or removing the mounting bolts such that the mounting bolts do not transfer the transformer vibrations to the enclosure. So, yes 100 kva, 1000 kva and even 5000 kva dry type air cooled electrical power transformers do have mounting feet. And yes the mounting bolts should be loosened or removed per the manufacturer’s instructions.

MIDWEST was asked if we ever rejected a transformer even though it passed all our electrical tests.  The answer was “yes.”  We scrapped an old 1000 kva dry type transformer used in a fairly clean room.  We had purchased the old transformer after replacing it with a larger unit in a paper mill.  The transformer was trucked to MIDWEST.  But an outer high voltage winding had physical damage that was found during the “hard focus” visual inspection. The riggers had damaged the outside of one winding with the tie down chains.  All the standard test results were very good.  And we energized the transformer at full voltage.  Everything tested out great.  But our inspection told us the transformer could not be used.  It was junk. Not worth repairing. It had what we call an “Incipient Failure.”  It was damaged and was going to fail.  When, who knows.  A day, a week, two years?  We didn’t know.  But we did know it was not reliable.  The high voltage windings were going to fail, short out.  It was just a matter of time before the used transformer became scrap.  We just hurried it up and declared it junk.  Here is another great example of pure technical knowledge just not being enough.  Experience and Knowledge were needed.