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A power transmission line feeds input power at 3300 V to a step-down transformer with its primary windings having 2000 turns. What should be the number of turns in the secondary in order to get output power at 330 V?

Asked in GSEB Board March 2020 · Transformers

• (1) 200
• (2) 400
• (3) 33
• (4) 40

Step-by-step solution

Why the other options are wrong

• (2) No single slip gives 400. Sanity check: 400 turns would give Vₛ = 3300×(400)/(2000) = 660 V, twice the voltage wanted.
• (3) No single slip gives 33. Sanity check: 33 turns would give only 3300×(33)/(2000) ≈ 54 V.
• (4) No single slip gives 40. Sanity check: 40 turns would give only 3300×(40)/(2000) = 66 V.

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