Where an ac transformer arc welder has a 50-ampere rated primary current and a 60 percent duty cycle, determine the minimum size copper 60 deg. C rated conductors required to supply this welder.
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✓ Correct answer: C. 8 AWGThe loads on transformer arc welders are considered intermittent. <br/><br/>Therefore, the minimum ampacity of the branch-circuit conductors is permitted to be determined by applying the percentage values shown in Table 630.11(A). This calculation is done by selecting the appropriate factor from the table, based on the duty cycle and type of welder, then multiply by the value of the welder rated primary current. The conductors are to be selected from Table 310.16.<br/><br/>.78 (duty cycle factor) x 50 amperes (primary current) = 39 amperes<br/><br/>Table 310.16 requires size 8 AWG 60°C rated conductors.
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