Journeyman Electrician Practice Exam

Question: 1 / 400

What is the full-load running current of a 208-volt, 3-phase, 50 hp, continuous-duty squirrel-cage AC motor?

120 amperes

143 amperes

To determine the full-load running current of a 208-volt, 3-phase, 50 hp continuous-duty squirrel-cage AC motor, you can use the formula for calculating the current in a three-phase motor:

\[ I = \frac{P}{\sqrt{3} \times V \times \text{efficiency} \times \text{power factor}} \]

Where:

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

- \( P \) is the power in watts (1 horsepower is approximately 746 watts),

- \( V \) is the voltage.

For a 50 hp motor, the power in watts would be:

\[ P = 50 \, hp \times 746 \, watts/hp = 37,300 \, watts. \]

Using the formula, and assuming a typical efficiency of around 0.90 and a power factor of about 0.85 for a standard squirrel-cage motor, the calculation proceeds as follows:

First, calculate the apparent power \( P \) in watts:

\[ P = 50 \times 746 = 37,300 \, watts. \]

Next, input the values into the formula:

\[ I = \frac{37

Get further explanation with Examzify DeepDiveBeta

156 amperes

170 amperes

Next Question

Report this question

Download Journeyman Electrician Practice Exam PDF Study Guide
Subscribe

Get the latest from Examzify

You can unsubscribe at any time. Read our privacy policy