Industrial Maintenance Technician Practice Test

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.