To order a transformer, we need to know primary voltage and secondary voltage. What is the third most important requirement?

To order a transformer, we need to know primary voltage and secondary voltage. What is the third most important requirement?

• A. Physical size
• B. V.A. rating
• C. Size of terminals
• D. Turns ratio

Answer: (B)

The key idea is how much power the transformer must deliver. After you know the primary and secondary voltages, the next crucial requirement is the VA rating (apparent power). This rating sets how much current the transformer can supply safely and, in turn, influences its size, insulation, and cooling needs. If the transformer is undersized in VA, it won’t handle the load current without overheating or voltage drop, even though the voltage values are correct. The turns ratio is determined by the voltage relationship you’ve chosen, so it isn’t the third independent requirement, and physical or terminal sizes follow from the VA rating rather than being separate constraints.

The key idea is how much power the transformer must deliver. After you know the primary and secondary voltages, the next crucial requirement is the VA rating (apparent power). This rating sets how much current the transformer can supply safely and, in turn, influences its size, insulation, and cooling needs. If the transformer is undersized in VA, it won’t handle the load current without overheating or voltage drop, even though the voltage values are correct. The turns ratio is determined by the voltage relationship you’ve chosen, so it isn’t the third independent requirement, and physical or terminal sizes follow from the VA rating rather than being separate constraints.