Effect of load reduction on the number of installed fins/radiators.

[ProfT]

Hi,

I'm overseeing the installation of a power transformer. At full-load, this is a 7.5 MVA 30/6.6 kV transformer. However, the prospective load is roughly 2.5 MVA. How can I go about calculating the copper losses of this transformer if I have the winding resistances. Is it correct to say, copper losses=I2R+I2R (primary and secondary losses)?

Your assistance will be highly appreciated.

Regards,

 

[waross]

Load ratio squared. 1/3 load, 1/9 copper losses. (This neglects excitation current losses.
Generally all the radiators and/or fins would be installed. The fans may not all be installed.

Bill
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"Why not the best?"
Jimmy Carter

 

[ProfT]

Thank you.

I left out some piece of info. Not all fins can be installed due to repair issues. It is a relatively old transformer and the fins are rusted. Sandblast and painting introduces leaks (we test one). So what you are saying is that the copper losses will be a ninth of the losses at full load?

 

[waross]

If I is 1/3, I² will be 1/9.

Bill
--------------------
"Why not the best?"
Jimmy Carter