Journeyman Electrician Practice Exam

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:

\[ I = \frac{90,000}{\sqrt{3} \times 208} \]