Heating, Ventilation, and Air Conditioning (HVAC ) Electrical Practice Test

Transformers are rated according to which specification?

1. Voltage at the primary

2. Current rating

3. VA at the secondary

4. Wattage output

The correct answer is: VA at the secondary

Transformers are primarily rated in volt-amperes (VA) at the secondary side because this measurement represents the capacity of the transformer to handle electrical load without overheating and while maintaining efficiency. The VA rating indicates both the voltage and current that a transformer can handle simultaneously, which is crucial for understanding how much power can be safely drawn from the secondary side of the transformer. While the voltage at the primary side is important for installation and connecting to the power supply, the VA rating is a more comprehensive measure of a transformer's performance and capability. The current rating, while relevant, does not provide a complete picture of the transformer's performance across varying voltage levels. Wattage output, similar to being linked with load calculations, is less commonly used for transformer rating since it can fluctuate depending on the power factor of the load. Therefore, the VA rating is the most appropriate and standardized specification for transformer ratings.