If a transformer has a VA rating of 1,500, a source voltage of 480VAC and the output voltage is 240VAC, what is the approximate maximum current that can be safely delivered by the transformer?

If a transformer has a VA rating of 1,500, a source voltage of 480VAC and the output voltage is 240VAC, what is the approximate maximum current that can be safely delivered by the transformer?

• A. 1 amp
• B. 6 amps
• C. 10 amps
• D. 3 amps

Answer: (B)

The output current a transformer can safely deliver is found from its VA rating and the output voltage. The VA rating represents the maximum apparent power on the output side, so Iout ≈ VA / Vout. With 1,500 VA and an output of 240 V, Iout ≈ 1500 / 240 ≈ 6.25 A, which is about 6 A. This is the current available to the load on the secondary side. The primary current would be about 1500 / 480 ≈ 3.1 A, but the question focuses on the output current.

The output current a transformer can safely deliver is found from its VA rating and the output voltage. The VA rating represents the maximum apparent power on the output side, so Iout ≈ VA / Vout. With 1,500 VA and an output of 240 V, Iout ≈ 1500 / 240 ≈ 6.25 A, which is about 6 A. This is the current available to the load on the secondary side. The primary current would be about 1500 / 480 ≈ 3.1 A, but the question focuses on the output current.