A transformer rated ___ kVA or larger shall be provided with a nameplate giving the name of the manufacturer, rated kVA, frequency, primary and secondary voltage, and the impedance of the transformer.

A transformer rated ___ kVA or larger shall be provided with a nameplate giving the name of the manufacturer, rated kVA, frequency, primary and secondary voltage, and the impedance of the transformer.

• A. 112.5 kVA
• B. 25 kVA
• C. 50 kVA
• D. 33 kVA

Answer: (B)

Transformers need a nameplate that shows essential data so technicians can verify ratings and perform safe system analysis, including fault calculations and protection coordination. The data typically required are the manufacturer, rated kVA, frequency, primary and secondary voltages, and the impedance, which is used to determine fault currents and voltage drop under load. The standard sets this nameplate requirement for transformers rated at 25 kVA or larger, making 25 kVA the minimum size that triggers the requirement. Any transformer at or above that size must have the nameplate; larger sizes would also meet the requirement, but the 25 kVA threshold is the point at which the rule begins.

Transformers need a nameplate that shows essential data so technicians can verify ratings and perform safe system analysis, including fault calculations and protection coordination. The data typically required are the manufacturer, rated kVA, frequency, primary and secondary voltages, and the impedance, which is used to determine fault currents and voltage drop under load. The standard sets this nameplate requirement for transformers rated at 25 kVA or larger, making 25 kVA the minimum size that triggers the requirement. Any transformer at or above that size must have the nameplate; larger sizes would also meet the requirement, but the 25 kVA threshold is the point at which the rule begins.