What is the turns ratio if the primary phase voltage is 480V and the secondary phase voltage is 240V?

To determine the turns ratio of a transformer, you can use the relationship between the primary and secondary voltages. The turns ratio (N) can be calculated using the formula:

[ N = \frac{V_{primary}}{V_{secondary}} ]

In this case, the primary phase voltage (Vprimary) is 480V and the secondary phase voltage (Vsecondary) is 240V. Plugging in these values:

[ N = \frac{480V}{240V} = 2 ]

This means that for every 2 turns in the primary winding, there is 1 turn in the secondary winding, which gives a turns ratio of 2:1.

Understanding this turns ratio is crucial because it illustrates how voltages change in relation to the number of turns in each winding. When the primary voltage is higher than the secondary voltage, as in this case, the transformer is a step-down transformer, which reduces voltage. Therefore, option B is the correct choice, representing a fundamental principle in transformer operation.