I have a transformer (15 KVA, High volt 240/480, Low volt 120/240, single phase) that I am trying to determine if it is going bad. It is fed from 460 Vac, secondary voltage is 240 Vac.The transformer feeds a UPS system for a computer server room. The UPS occasionally shuts down due to voltage outside of tolerance. I have been using a Fluke model 43 power quality analyzer to test the output voltage. I had the tester on the primary and secondary for a couple of weeks on each side. The primary never showed any noticeable power fluctuations. The secondary showed some power dips as low as around 198 Vac. I checked all connections several time to be sure of them. They all look good. Is this an indication that the transformer is going bad ? Before I spend the money on a new transformer I just want a little bit more to go on. Thanks for any help.
How to properly test a transformer for clean output.
- Thread starter steve61
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
So when the secondary voltage dropped to 198 volts the primary was still at 480?
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
(You say power in some places and voltage in others.)
Is the transformer sized for the UPS and not otherwise overloaded? How big is the UPS?
What are the current readings and the load on the UPS? Could be that the UPS gets a heavy load or that the input side of it is causing a heavy draw and pulling down the voltage.
Is the transformer sized for the UPS and not otherwise overloaded? How big is the UPS?
What are the current readings and the load on the UPS? Could be that the UPS gets a heavy load or that the input side of it is causing a heavy draw and pulling down the voltage.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
The only way to test a transformer is with a dedicated meter, often called a TTR even though it does more.
Transformers do not usually go bad except for turn to turn faults which change the ratio of the transformer.
It takes a lot of loading, including harmonics, to force a power transformer into saturation, so most voltage regulation issues are from the loading. Have you gotten any waveforms when loaded and unloaded.
Transformers do not usually go bad except for turn to turn faults which change the ratio of the transformer.
It takes a lot of loading, including harmonics, to force a power transformer into saturation, so most voltage regulation issues are from the loading. Have you gotten any waveforms when loaded and unloaded.