Master Electrician Practice Exam

To determine the minimum required kVA rating for a transformer supplying a secondary balanced load of 416 amperes per phase, it is essential to use the formula for calculating kVA, which is:

\[ kVA = \frac{Volts \times Amps}{1000} \]

Assuming a typical secondary voltage of 480 volts for three-phase systems, the calculation for each phase would be:

1. First, we find the total current for a three-phase load, which is computed as \( \text{Total Amps} = \sqrt{3} \times \text{Phase Amps} \) for balanced loads. However, since we already have the demand load per phase, we can directly use the given load.

2. Plug in the values:

\[ kVA = \frac{480 \, \text{Volts} \times 416 \, \text{Amps}}{1000} \]

\[ kVA = \frac{199680}{1000} \]

\[ kVA = 199.68 \]

This value rounds up to approximately 200 kVA. In practice, transformers are selected based on standard size increments, which means the minimum required rating