Question

An AC non motor-generator arc welder on an individual circuit has a nameplate primary current of 100A and a duty cycle of 70%. The branch circuit conductors must be a minimum size ___ AWG THHN copper. select one:

a. # 3 AWG
b. # 4 AWG
c. # 6 AWG
d. # 8 AWG

Answer 1

For an AC non-motor-generator arc welder with a nameplate primary current of 100A and a duty cycle of 70%, the minimum size for the branch circuit conductors must be #3 AWG. So, the correct option is a. # 3 AWG.

Step-by-step explanation:

To determine the minimum size for the branch circuit conductors, you must consider the primary current and duty cycle of the welder, along with the appropriate wiring regulations, such as the National Electrical Code (NEC). Since the welder has a primary current of 100A and a duty cycle of 70%, and assuming we aim to use 80% of the allowable ampacity for continuous loads, we apply the following calculation:

100A * 70% = 70A for the duty cycle

70A / 0.80 (80% capacity) = 87.5A, which would be the minimum ampacity required. According to the NEC tables, a #3 AWG THHN copper wire supports up to 115A. Therefore, this size would be adequate for a welder with a 70% duty cycle and a primary current of 100A.