Oklahoma Electrical Practice Exam

In a 3 phase, 480 volt delta system with a balanced load, what is the line current for a total load of 80,000 VA?

1. 75 amps

2. 85 amps

3. 96.22 amps

4. 100 amps

The correct answer is: 96.22 amps

To determine the line current in a 3-phase, 480 volt delta system with a balanced load, we use the formula that relates power, voltage, and current in a three-phase system: \[ P = \sqrt{3} \times V_{line} \times I_{line} \] Where: - \( P \) is the total power in watts (or VA), - \( V_{line} \) is the line-to-line voltage, - \( I_{line} \) is the line current. In this case, the total load is 80,000 VA, and the line-to-line voltage for the delta system is 480 volts. Rearranging the equation to solve for the line current yields: \[ I_{line} = \frac{P}{\sqrt{3} \times V_{line}} \] Substituting the known values: \[ I_{line} = \frac{80,000}{\sqrt{3} \times 480} \] Calculating the term \( \sqrt{3} \approx 1.732 \), we find: \[ I_{line} = \frac{80,000}{1.732 \times