Why is there a line that conductors aren't supposed to be above in transformers?

[rhamblin]

Random question here. Why is there a line in dry transformers that conduits aren't supposed to be above? I remember talking about this back in apprenticeship school, but never figuring out the reason. I'm thinking because of the heat that the coil creates, might damage the wires? But 90°C wires should be able to handle any heat a transformer could create can't they? Transformers don't get that hot do they?

 

[infinity]

Some have them some don't. Not sure why.

 

[jumper]

Quick search of install manuals did not really answer the question. Some allude to heat and some to cable radius bending. Nothing definitive that I found.

 

[Ingenieur]

Looks like they can get pretty hot
150-200 C
and that assumes adequate ventilation
http://apps.geindustrial.com/publib...nstallation and Instruction|475A667AAP001|PDF

 

[jumper]

Looks like they can get pretty hot
150-200 C
and that assumes adequate ventilation
http://apps.geindustrial.com/publib...nstallation and Instruction|475A667AAP001|PDF

Yep, but this was their info also:

All cable connections to the transformer should be brought into the enclosure as low as possible to allow for the required cable
bending radius. Side entry of cables is recommended as it leaves the ventilation areas unobstructed.

So heat or bending radius?:?

 

[Ingenieur]

Yep, but this was their info also:



So heat or bending radius?:?

not mutually exclusive
both
tight radius + high temp = more likely insul damage?
cracking, expansion/contraction, vibration, etc

 

[rhamblin]

Thanks for the replies guys, always kinda wondered.