Industrial Maintenance Technician Practice Test

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Question: 1 / 400

In a 480 volt three-phase system, what would the meter read if you measured from one leg to ground?

120 volts

240 volts

277 volts

In a 480 volt three-phase system, the voltage measured from one leg to ground is typically 277 volts. This is derived from the relationship between the line-to-line voltage and the line-to-ground voltage in a three-phase system.

In a three-phase system, the line-to-line voltage is the applied voltage between any two of the three phases. For a 480 volt three-phase system, the line-to-ground voltage is calculated using the formula:

\[ V_{lg} = V_{ll} / \sqrt{3} \]

Where $ V_{lg} $ is the line-to-ground voltage, and $ V_{ll} $ is the line-to-line voltage. Substituting 480 volts into the equation gives:

\[ V_{lg} = 480 / \sqrt{3} \approx 277 \text{ volts} \]

Therefore, if you measure from one leg to ground in a 480 volt three-phase system, the meter would read approximately 277 volts, making this the correct choice.

Industrial Maintenance Technician Practice Test

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