Master Electrician Exam 2025 – 400 Free Practice Questions to Pass the Exam

Question: 1 / 400

What is the approximate full-load ampere rating of the primary side of a 150 kVA service transformer with a 480Y/277 volt 3-phase primary?

150 amperes

180 amperes

To determine the approximate full-load ampere rating of the primary side of a 150 kVA service transformer with a 480Y/277 volt 3-phase primary, the correct calculation involves using the formula for three-phase systems:

\[ I = \frac{P_{kVA} \times 1000}{\sqrt{3} \times V} \]

Where:

- \( I \) is the current in amperes,

- \( P_{kVA} \) is the power rating of the transformer in kilovolt-amperes,

- \( V \) is the line-to-line voltage.

For this transformer:

- \( P = 150 \, kVA \),

- The line-to-line voltage \( V = 480 \, volts \).

Substituting the values into the formula:

\[ I = \frac{150 \times 1000}{\sqrt{3} \times 480} = \frac{150000}{830.84} \approx 180 \, amperes \]

This calculation confirms that the full-load ampere rating of the primary side of this transformer is approximately 180 amperes, which aligns with the selected answer. This number is crucial for assessing the electrical load capacity

Get further explanation with Examzify DeepDiveBeta

200 amperes

220 amperes

Next Question

Report this question

Download Master Electrician Practice Exam PDF Study Guide
Subscribe

Get the latest from Examzify

You can unsubscribe at any time. Read our privacy policy