R-7 Phase a Matic wiring....?

[Perryk]

Hello,

Quick question on wiring size....

I have a R-7 phase converter....and according to their Phase A Matic formula I need wiring for around 25 amps.

FLA= 10amps

FLA x 1.5 + 5amps idle for converter +20%

(10*1.5+5) x 120%= 24amps

I need 75' of wire to get my 220v single over to my R-7.

What size of wiring would I need? and how do I account for start amperage vs FLA?

My machine is a 3hp lathe...

Thanks

 

[matt_i]

I would run #10 thhn in conduit. The big draw is when the idler is started up...there's a locked rotor condition for a second or two with big inrush until the start capacitor kicks in to shift the 3rd phase and get the idler running. The idler will draw very low current as it is just spinning the motor shaft and no actual mechanical work. Also, just to mention that a 3phase motor which runs from a single phase will never make full nameplate power. 2/3 is a good estimate.