Electrical Troubleshooting Quiz

In the last 18 months, a 75kVA dry-type transformer has had to be replaced twice. It's mounted in the ceiling of the facility's data processing room. There is a small UPS system in the room, but it doesn't provide enough ride-through for the time it takes to complete a transformer replacement.

A proposed solution was to run an alternative power line to the room, but replacing the transformer would still be highly disruptive. It's overhead work, so the people who normally work in that room would need to move their workstations and some equipment out to the corners.

How can you prevent a repeat of this, with the transformer that's now installed?

You need to move that transformer so it's not over the work areas. Transformers are often tucked into the ceiling to save room, but thermal considerations can render that a poor solution. Wherever you mount the new transformer, ensure it has adequate airflow around it. Install temperature monitoring, and for the first year conduct monthly thermal imaging.

Because the room is full of switching power supplies, use this project as an opportunity to derate the transformer and the conductors for harmonic content. If the derating calculations show the 75kVA is undersized, you've found your root problem. Look at the transformer secondaries with power analyzer and discuss your findings with the UPS vendor.

The alternative line is a good idea. But only if you install an automatic transfer switch to ensure smooth transition of the load to this secondary source and back again.