Epoxy Shielded Transformers

[richanton]

Federal Pacific sells a product called "epoxy shielded" power transformers that they claim are better and cheaper than cast coil transformers. Any opinions on these. My application is for 2500kva size units that will be installed outdoors. I'm looking for alternates to using oil-filled transformers due to the problems of oil containment. Right now, my plan is to use a cast coil design.

 

[CHDean]

Cheaper yes, better is a relative statement.
What you are looking at is most likely a VPI dry-type with an additional epoxy insulation coating. If cost is the prime factor in making your choice you will not have to look farther. True cast coil designs will have cast primary and secondary coils and tend to be very pricey. But as with most things, you get what you pay for. Cast coils have very high mechanical strength and are immune to most environmental issues. There are designs that use epoxy fillied secondary windings to reduce cost but have reduced benifits. If your budget can stand it cast coil is a solid choice to make. One consideration you must keep in mind is the ANSI insulation level (BIL) rating. Dry and cast coil transformers have lower BIL ratings than oil unless you specify them higher. It's also worth the money to get a higher BIL