An Electrical Contractor called MIDWEST with an emergency. A customer lost a 1500 kva dry type power transformer. The voltage was 13,200 to 480. Two of the fuses in the primary load break switch had blown. They checked things out and couldn’t find anything wrong, but wanted MIDWEST to test the transformer anyway. Meanwhile they checked out the secondary switchgear and a 480 volt to 208 volt dry type transformer in the same room as the switchgear. They found no smell and no smoke, so they figured they might get lucky, although we both knew that was not very probably. When 15kv, 100 amp fuses blow, a lot of energy went somewhere. The 1500 kva dry type transformer was a typical indoor unit substation type, with LAs, cooling fans and a fan control package. When we got there, the electrical contractor already had the panels off the switchgear and transformer, and everything properly grounded. They offered to help haul up the test equipment, which is always nice, but we said to hold off for a minute. It took 15 seconds to get our flashlight and then it took another 15 seconds to inspect the transformer and tell them the transformer had failed and they needed to get a replacement transformer or a rental transformer. Their skepticism was obvious, and for good reason. But we showed them the debris that had blown out the bottom of the center high voltage winding. Then had them look down through ventilation ports of the blown high voltage winding so they could see the blown out turns within the high voltage winding. They understood immediately. We ran a quick turns ratio test to document the failure. A case of seeing is believing.
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.
Categories: Uncategorized Tags: 100 KVA Transformer, 1000 kva dry type transformer, 1500 KVA Transformer, 5000 KVA Dry Type Air Cooled Transformer, Dry Type Electrical Power Transformer, electrical power transformer, Excessive Mechanical Vibrations, Mounting Bolts, Mounting Feet, new transformer, Replace Failed Transformer, Transformer Mounting Feet, Vibration Dampening Pads