Corrugated wall transformers

[norcalnewb]

Has anyone had recent experience with a corrugated wall transformer design?

 

[argotier]

That type is very popular in my IEC based country for "off-the-shelf" distribution transformers up to 1250 kVA and 33 kV, with or without conservator tank.

Without conservator they are the most economical option, with reduced dimensions and low maintenance.

I guess they are more rare in ANSI world. What is troubling you?

 

[norcalnewb]

I have seen this design in smaller, utility style pad mounted transformers, but in general, we don't see them in substation transformers. In what applications are these used in your country? Industrial plants tend to be a bit more conservative in nature and not use "new" designs, so there is some concern about the reliability when placed in a harsh environment.

 

[argotier]

They are most usual for distribution grids (mostly residential and low consumer commerces/industries) in both overhead and subterranean applications.

In substations or big industries they are still used for auxiliary services within the power and voltage range I've said (up to 1250 kVA and up to 33 kV).

The corrugated wall have two functions:

1 - Heat dissipation: It's a low cost solution as they work as tank wall and radiator (a lot of material saving), but it's limited to trx of a few MVAs as much, beyond that it becomes impractical.
2 - Oil volume compensation: In hermetically sealed design (like the picture above), where the trx tank is completely filled with oil (there is no gas blanket, as usually goes in ANSI world), they have also the function of compensating for the oil expansion as those fins are flexible (to some extent).

Some costumers don't like this design for this #2. Flexible tank walls means that the vacuum/pressure tests you can apply to this design are much lower than in a traditional one and if not correctly designed you could have sealing problems in extreme service conditions (very low ambient temperature and unloaded or high temperature and full loaded). Adding a conservator or a gas blanket might help with the latter.

Hope it helps.

 

[cuky2000]

Below are some of the salient characteristics of the corrugated distribution transformer. The closest counterpart in the ANSI marketplace is the pad-mounted transformer type for three-phase distribution application.
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