I am more familiar with single phase buck boost transformers. I understand that to buck voltage to a 3 phase compressor, I will need two single phase autotransformers.
My compressors are 4.9A each. There are 2 compressors so a RATED load of 9.8A. The autotransformers I have access to are rated for 10.9A loads or 21.9A loads. I will have to use the larger 21.9A rated bucking transformer.
The max circuit breaker I can use for this autotransformer is 30A. I want to protect the autotransformer and not have any nuisance trips. Do I size the primary autotransformer OCPD of the secondary load, as long as it is below the max 30A?
Would these calculations work: 4.9A * 2.25 = 11.025 + 4.9A = 20A primary
Also, I see in NEC 450.4 information about OCPD's for the primary. Am I also able to put breakers on the secondary? For example, I have 2 compressors, can I put 10A UL489 breakers on each branch of the secondary?
My compressors are 4.9A each. There are 2 compressors so a RATED load of 9.8A. The autotransformers I have access to are rated for 10.9A loads or 21.9A loads. I will have to use the larger 21.9A rated bucking transformer.
The max circuit breaker I can use for this autotransformer is 30A. I want to protect the autotransformer and not have any nuisance trips. Do I size the primary autotransformer OCPD of the secondary load, as long as it is below the max 30A?
Would these calculations work: 4.9A * 2.25 = 11.025 + 4.9A = 20A primary
Also, I see in NEC 450.4 information about OCPD's for the primary. Am I also able to put breakers on the secondary? For example, I have 2 compressors, can I put 10A UL489 breakers on each branch of the secondary?