Can you calculate the energy loss of two 2 KVA BB transformers that operate 12 hours a day 6 days a week, 50 weeks for us? Fill in the blanks that are needed. I chose 2 KVA at random.
Assuming a pair of 2 KVA transformers to take 208V to 230V. This gives a load current of 75A, somewhere in the 25 or 30 Hp range.
Figure the transformers will have 5% core loss, running 24x7. So I estimate 200W * 8766 hours = 1750 kWh just to have the transformers present.
Figure the transformers will have another 10% copper loss when the load is on. So 400W * 12 * 6 * 50 = 400W * 3600 hours = 1440 kWh of losses when the transformers are loaded.
The load itself is assumed to be 24 kW, so 24 * 3600 = 86400 of real consumption.
So tacking the buck-boost transformer on adds 3.7% to energy use.
More realistically, the compressor won't be running full time during a shift. So the 1440 kWh of copper loss and the 86400 kWh of consumption both go down proportionally with run time. But the core loss is constant unless you put the transformers downstream of the control contactor (meaning the contactor has to deal with transformer inrush and higher current, not a good idea). Say the compressor runs 30% of the time...that core loss factor has now jumped to nearly a 7% energy use adder.
So IMHO the additional losses to using buck/boost transformers with the 'wrong' compressor are not huge in a relative sense, but also not insignificant.
-Jon
