welder calculation

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perlin68

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I have a welder with a primary side of 208V, 115A, 21.8kw, 23.9kva. The secondary side has; 40V AC, 30V DC, 300A, Duty cycle 60%, max ocv(?) 80. Then at the bottom of the name plate it reads; Duty cycle 125% rated output 35%. Welding range inert gas 5 to 460. The owner does not have the owners manual, and it has a 50 amp 3 wire cord already on it.
The welder is supplied with 3 #6 thhn conductors on a 50 amp breaker. This appears to be fine under normal use, however, when they try to turn up the welder to weld aluminum they overload the circuit. At this setting the welder is using 88 amps.
Suggestions? I have read art 630.11(A) and the calculation is a little confusing to me. Any help would be greatly appreciated.
 
Without nameplate information you'd take the 115 amps times the duty cycle miltiplier, .78 for 60%, and find your wire needs to have an ampacity of 90 amps. Your OCPD would be sized according to 630.12, and 200%x115amps = 230 amps.

That's the general approach, you should be sure it's an arc welder and read the entire Part II.

Jim T
 
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