- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
I posted the original TP-1 reference, I am well aware that it is an average over a period.But the 35% isn't a single point. It's average loading over a 24-hour period.
You'd need to have a 24-hour load profile to work out what the optimum design was for least energy losses over a typical 24-hour period.
No-load losses are primarily Fe losses. I don't quite see how reducing Cu I2R losses would or should increase Fe losses but I'm not a transformer designer.
Maybe you could explain?
Mike_Kilroy already explained there is a tradeoff between conductor and core sizing. There are physically more materials required to build a 500kVA unit then are required to build a 150kVA unit. Like most items there is no single 'always' correct answer for transformer sizing, but once you start to limit the number of variables, it becomes easier to find a correct answer. For a specific loading profile of <50% (ave over 24hr) an oversized transformer is typically a waste energy. Likewise for a loading profile of >95% fed by a transformer with little to no oversizing.
Most general purpose transformers have been wound with aluminum conductors for the past 50 years or so.
It has been decades since I was able to cost justify copper over aluminum windings based strictly on I?r losses and the resulting 'energy bill' savings.