Final answer:
The phase voltage for a 3-phase, 4-wire, 240V system is calculated by dividing the line voltage by the square root of 3, resulting in approximately 138.56V. A good reading for the phase voltage should be close to this value.
Step-by-step explanation:
The phase voltage across a single phase to neutral for a 3-phase, 4-wire, 240V system can be calculated by dividing the line voltage by the square root of 3 (assuming it is a balanced Y-connected system). This is because in a 3-phase system, the line voltage is greater than the phase voltage by a factor of the square root of 3. The formula for this calculation is:
Phase voltage = Line voltage / √3
For a 240V line voltage, the phase voltage would be:
Phase voltage = 240V / √3 ≈ 138.56V
A good reading for the phase voltage would be close to this calculated value of approximately 138.56V.