Buck Boost Transformer

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czars

Czars
Location
West Melbourne, FL
Occupation
Florida Certified Electrical Contractor
I have a client that has purchased a 230V air compressor. Unfortunately, his shop is supplied with 120/208 3 phase. The motor manufacturer states that the motor will not run properly on 208V. My client wants to utilize a Buck Boost transformer to generate 240V from the 208V. The motor FLA is
21A, so thats 4830KVA. Does he need a transformer larger than 5KVA in order to handle the higher motor starting current?
 
czars said:
I have a client that has purchased a 230V air compressor. Unfortunately, his shop is supplied with 120/208 3 phase. The motor manufacturer states that the motor will not run properly on 208V. My client wants to utilize a Buck Boost transformer to generate 240V from the 208V. The motor FLA is
21A, so thats 4830KVA. Does he need a transformer larger than 5KVA in order to handle the higher motor starting current?
Click to expand...

Nope, first, I am assuming that you are referring to a single phase air compressor. That is good, because the single, reasonably constant load is the ideal application for a boosting transformer. However your calculation is wrong. The actual size required is 240-208=22 volts change in voltage, times 21 full load amps for a transformer size of 672 volt-amps. 1KVA buck boost transformer will do just fine.

You see, the transformer is not an isolation transformer carrying the entire load of the equipment, it only "sees" the change in voltage.
 
Thanks for the info. Never dawned on me to use the difference in voltage. After looking at various transformer sites, I am not armed with better info.
 
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