Fundamentals of Electrical Engineering Unit 3 – Transformers: important questions for AKTU
Unit 3 (Transformers) questions that AKTU repeats most often. This unit carries about 24 marks per paper. Start with the repeated questions, then the most asked topics.
Most repeated Unit 3 questions
- State the significance of voltage regulation of transformer. A 4kVA, 200/400V, 50Hz single phase transformer has equivalent resistance referred to primary as 0.15Ω. Calculate: (i) Total copper losses on full load. (ii) Efficiency at full load 0.9 pf lagging. (iii) Efficiency at half load 0.8 pf leading. Assume total iron losses = 60W. (10 marks, 2022, Transformer Losses and Efficiency) – also asked in 2022, 2023, 2024, 2025, 2026
- What is the purpose of an equivalent circuit of a transformer? Obtain the approximate equivalent circuit of a transformer as referred to the primary with all necessary parameters. (10 marks, 2022, Transformer Losses and Efficiency) – also asked in 2022, 2023, 2024, 2025, 2026
- A 20kVA, 2000V/200V, single-phase, 50Hz transformer has primary resistance 1.5Ω and reactance 2Ω. Secondary resistance 0.015Ω and reactance 0.02Ω. No load current 1A at 0.2 pf. Determine: (i) Equivalent resistance, reactance and impedance referred to primary. (ii) Supply current. (iii) Total copper loss. Draw approximate equivalent circuit. (10 marks, 2022, Transformer Losses and Efficiency) – also asked in 2022, 2023, 2024, 2025, 2026
Most important Unit 3 topic
- Transformer Losses and Efficiency (Unit 3: Transformers) – asked 23 times in 2022, 2023, 2024, 2025, 2026
Most asked Unit 3 topics
- Transformer Losses and Efficiency – asked 23 times
- Ideal and Practical Transformer – asked 16 times
- Magnetic Circuits
More Unit 3 previous year questions
- What are the main parts of a transformer and how does it work? (2 marks, 2026, Ideal and Practical Transformer)
- The following results were obtained on a 5 kVA, 2400/120V transformer: Open circuit test 120V, 9.65A, 396W instrument on l.v. side. Short circuit test 92V, 20.8A, 810W instrument on h.v. side. Determine: (i) the circuit constants (ii) efficiency at half load, 0.8 p.f. lagging (iii) regulation at 0.8 p.f. lagging (7 marks, 2026, Transformer Losses and Efficiency)
- Explain operating principle of transformer and derive the equation for induced emf in a two-winding transformer. Also discuss the term regulation and efficiency w.r.t. transformer. (7 marks, 2026, Ideal and Practical Transformer)
- The efficiency of a 400 kVA 1-ϕ transformer is 98.77%, when delivering full load at 0.8 p.f. and 99.13% at half of the full load and unity power factor. Calculate (i) Iron loss (ii) Full load copper loss. (7 marks, 2026, Transformer Losses and Efficiency)
- Draw the phasor diagram of practical transformer at no load condition. (2 marks, 2025, Ideal and Practical Transformer)
Unit 3 syllabus topics
- Magnetic Circuits
- Ideal and Practical Transformer
- Transformer Losses and Efficiency