Fundamentals of Electrical Engineering Unit 3 – Transformers: AKTU previous year questions
39 AKTU questions from Unit 3 (Transformers) asked in 2022–2026, tagged by marks, year and topic. In short: about 24 marks of every paper come from this unit; the most asked topic is Transformer Losses and Efficiency (23 times); 36 questions came back in a later year. The latest ones are listed below; on the page you can filter them by 2-mark or long questions, topic and repeats.
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)
- Write the condition for maximum efficiency of transformer. (2 marks, 2025, Transformer Losses and Efficiency)
- Draw the phasor diagram of a practical two-winding transformer in no-load condition. (2 marks, 2025, Ideal and Practical Transformer)
- Explain the working principle of transformer and derive the EMF Equation. (7 marks, 2025, Ideal and Practical Transformer)
- Describe different types of transformer losses and methods to minimize it. (7 marks, 2025, Transformer Losses and Efficiency)
- The primary and secondary windings of a 600 kVA transformer have resistance of 0.4 Ω and 0.001 Ω respectively. The primary and secondary voltages are 6000 V and 200 V respectively. The iron loss is 3200 W. Calculate the efficiency on full load at the load power factor being 0.8. (7 marks, 2025, Transformer Losses and Efficiency)
- A 100 kVA, single-phase transformer has an iron loss of 600 W and a copper loss of 1.5 kW at full-load current. Calculate the efficiency at (i) full load and 0.8 lagging pf, and (ii) half load and unity pf (7 marks, 2025, Transformer Losses and Efficiency)
- Why does not use of transformer in DC supply and derive the EMF equation? (7 marks, 2025, Ideal and Practical Transformer)
Most asked Unit 3 topics
- Transformer Losses and Efficiency – asked 23 times
- Ideal and Practical Transformer – asked 16 times
- Magnetic Circuits
Unit 3 question pattern
- 2-mark questions: 13 asked in 2022–2026
- 7-mark questions: 20 asked in 2022–2026
- 10-mark questions: 6 asked in 2022–2026
- About 24 marks from Unit 3 in every paper
- 36 questions were asked again in a later year
Unit 3 questions year by year
- 2026: 4 Unit 3 questions asked (23 marks across that year's papers)
- 2025: 8 Unit 3 questions asked (41 marks across that year's papers)
- 2024: 9 Unit 3 questions asked (48 marks across that year's papers)
- 2023: 8 Unit 3 questions asked (46 marks across that year's papers)
- 2022: 10 Unit 3 questions asked (68 marks across that year's papers)