On your transformer chart, in the three phase area, you have 3a Wire, 4b Raceway, and 5. EGC while on the 208 volt side, you have 3b Wire, 4b Raceway and 5. Are these correct and if so where is the corresponding notes at the bottom as there is no 3a or 3b and 4a and 4b has to do with wire size and not raceway. Just a little confusing...

I have become a Journeyman electrician in 1987. In 1999 I purchased one of Mike Holts books. I read it and it has helped me. In 2014 I reread it and took the Masters exam in the state of Michigan and passed. I have since been a fan of Mike Holt books and teachings. One problem that I still have is when calculating loads and applying all that I have learned and I come up with something different than the manufacturer has installed to their equipment that I am hooking up and responsible for.

example: I have a 12.5KVA Load at 230vac single phase. It goes to a Mag plate to hold dies in a CNC mill. Voltage available is 480vac. This Magnet is a continuous load. After my calculations the load comes in at 32.5amps @ 480vac. So I would size the conductors with a #8awg THHN on the primary of a 12.5KVA. This is what I believe to be correct for the primary. The Secondary current came out to be 67.92amps at 240vac. This would require a #4awg THHN. However, when I looked at the unit the manufacturer has placed a single phase #10awg 3 conductor Cable on the output to the mag unit. I will call Manufacturer soon however, I was hoping to get comments on others who have run into this problem.

Hi Mike, Could the 15KVA, 208V 3 phase secondary be 60 amps (not 50 amps)to match standard panel sizes?

How come no 600 V ? It is a Code Recognised voltage (347/600).

This is not a comment need some info what circuits in a dwelling require arc fault breakers

Mike, When you released the former version of the motor tables, I called your attention to the fact that 240.6(A) tells that ?Additional standard ampere ratings for fuses shall be 1, 3, 6, 10 and 601?. Please note that in the updated tables, this was considered for the single-phase motors, but not for the 3-phase motors. Any reason for that? Jacob Mendelovici

thanks