I've generally sized my wire for my 3ph machines just like I do for 1ph things. Look at total max load and pick a wire that's next up from that. But just a few minutes ago while looking at what I'll do to hook up a new lathe that is coming, I ended up a little puzzled. I know this matters very little on small equipment, and anything big will be 3ph anyway.(not considering voltage drop and such here)
So, If you have a 3ph motor of 7.5HP, 240V. You end up with about 23amps. Does each of the 3 load carrying wires ever see the full 23amps draw like a 1ph wire would?, or does it only see a faction of it on 3ph? I saw one formula while googleing a minute ago, that had a .866 factor into it for 3ph, so I'm thinking that you can actually figure a smaller load per wire?
Next part of the question would be in regard to a steady resistive load like a large electric water heater that was 3ph. Say it draws 100amps total, would you technically have to use wire that carries 100amps, or would you say each of those wires is only seeing a portion of the total amperage? and what would that portion normally be?
What made me think of this is that right now my two 3hp-3ph/240v machines are on 10Awg wire, and then I thought, how weird my new 7.5hp 3ph machine could also use this same 10awg wire, I thought I was gonna go with #8, but looks like I wouldn't really have to go that big, mostly if each wire doesn't even see the full 23amps.
Thanks for any info on this.
So, If you have a 3ph motor of 7.5HP, 240V. You end up with about 23amps. Does each of the 3 load carrying wires ever see the full 23amps draw like a 1ph wire would?, or does it only see a faction of it on 3ph? I saw one formula while googleing a minute ago, that had a .866 factor into it for 3ph, so I'm thinking that you can actually figure a smaller load per wire?
Next part of the question would be in regard to a steady resistive load like a large electric water heater that was 3ph. Say it draws 100amps total, would you technically have to use wire that carries 100amps, or would you say each of those wires is only seeing a portion of the total amperage? and what would that portion normally be?
What made me think of this is that right now my two 3hp-3ph/240v machines are on 10Awg wire, and then I thought, how weird my new 7.5hp 3ph machine could also use this same 10awg wire, I thought I was gonna go with #8, but looks like I wouldn't really have to go that big, mostly if each wire doesn't even see the full 23amps.
Thanks for any info on this.