Journeyman Electrician Practice Exam

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Get ready for the Journeyman Electrician Exam. Study with flashcards, multiple-choice questions, and detailed explanations. Prepare effectively and ensure success on your certification!

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What is the approximate current each ungrounded conductor carries at full-load in a 208Y/120-volt, three-phase service with a balanced net computed load of 90 kVA?

200 amperes
250 amperes
300 amperes
350 amperes

The correct answer is: 250 amperes

To determine the approximate current each ungrounded conductor carries at full load in a 208Y/120-volt, three-phase service with a balanced load of 90 kVA, it's essential to use the formula for three-phase power: \[ P = \sqrt{3} \times V_{L-L} \times I \] where $ P $ is the power in watts (or VA), $ V_{L-L} $ is the line-to-line voltage, and $ I $ is the current. Given that the service is 208Y/120 volts, the line-to-line voltage $ V_{L-L} $ is 208 volts. The power in kilovolt-amperes (kVA) can be converted into watts (W) since 1 kVA = 1000 VA. Therefore, 90 kVA becomes 90,000 VA. Rearranging the formula to solve for current $ I $: \[ I = \frac{P}{\sqrt{3} \times V_{L-L}} \] Substituting the given values into the formula: \[ I = \frac{90,000}{\sqrt{3} \times 208} \]