Transformers are rated by:

Transformers are rated by:

• A. Voltage at primary
• B. VA at the secondary
• C. Current at primary
• D. Power factor

Answer: (B)

A transformer’s capacity is defined by how much apparent power it can transfer, not by voltage alone or by the current alone. This capacity is expressed in volt-amperes (VA) and represents the maximum product of secondary voltage and secondary current the windings can carry safely without overheating. The rating is typically shown on the nameplate as a VA (or kVA) value for the secondary side, because that’s the measure of heat and practical load the transformer can handle. The primary voltage is determined by the source and the turns ratio, and the corresponding primary current is derived from the VA rating using I_primary = VA / V_primary. So the rating isn’t the primary current by itself. The power factor describes the mix of real and reactive power in the load and doesn’t set the transformer’s size; a given VA rating applies to loads with different PF, within the same heating limit. So, the correct concept is that transformers are rated by the VA capacity on the secondary side.

A transformer’s capacity is defined by how much apparent power it can transfer, not by voltage alone or by the current alone. This capacity is expressed in volt-amperes (VA) and represents the maximum product of secondary voltage and secondary current the windings can carry safely without overheating. The rating is typically shown on the nameplate as a VA (or kVA) value for the secondary side, because that’s the measure of heat and practical load the transformer can handle.

The primary voltage is determined by the source and the turns ratio, and the corresponding primary current is derived from the VA rating using I_primary = VA / V_primary. So the rating isn’t the primary current by itself. The power factor describes the mix of real and reactive power in the load and doesn’t set the transformer’s size; a given VA rating applies to loads with different PF, within the same heating limit.

So, the correct concept is that transformers are rated by the VA capacity on the secondary side.