Tranformer Circular Core vs. Rectangular Core 1

[coloradog1]

I am looking for information on the advantages (and disadvantages) of Circular core transformers versus rectangular core.

I have heard that circular offers technical advantages but the rectangular core is cheaper. Can someone provide feedback on this?

The applications I am most interested in are
5MVA-20MVA @ 46kv/4.16kV
100-200MVA @ 230/46kV

Any literature would be helpful also.

Thank you

 

[dpc]

Talk with Waukesha - they will be happy to explain the advantages of the circular core.

The primary benefit is short-circuit mechanical strength for through-faults. Waukesha used to claim that they had never had a through-fault failure on one of their units.

 

[electricuwe]

Well, there are other, very simple reasons:

For the same area (iron) the cirumference (copper, losses) for a circular core is less

Higher cost is due to more difficult manufacturing:
more different widths of iron, more care during stacking

But with raising cost for copper and energy no one should use rectangular cross sections for transformers above a few kVA

 

[apowerengr]

A good book on transformer engineering could help too as well as understanding different winding construction techniques for circular designs. Of the transformers you listed the only one I'd consider for rectangular designs is the 5 MVA 46-4.16kV unit and that recommendation assumes that you have an on-line backup for the unit. Anything larger or higher voltages requires, in my opinion, circular designs using disk or helically-constructed windings.

dpc, as for Waukesha's claim I've seen their mechanical through-fault failure first hand.........not any better than the rest in that regard although they've taken steps recently to improve their through fault mechanical performance.

 

[Zogzog]

I believe the only advantage of a rectangular core is the better use of physical space for vault considerations.

 

[jghrist]

The short circuit concerns with rectangular coils are not much of a problem if the low voltage coils are full width sheet type.