⚡ Transformer MCQs for PSU Exams Part 2⚡

⚡ Transformer Quiz – Part 2 (Q13–20) ⚡

👋 This is Part 2 of the transformer quiz. It covers saturation, phasor diagrams, tests, equivalent circuits, and voltage regulation. Complete this section to finish the full set!

13Can a 50 Hz transformer be used at 25 Hz with rated voltage? 🌀

a) Yes, current unchanged
b) No, flux doubles → saturation
c) No, resistance ↓ → current doubles
d) Yes, insulation safe

Check Answer

Answer: b) No, flux doubles → saturation
Explanation: Flux ∝ V/f. At half frequency, flux doubles → core saturation.

14On load phasor diagram of transformer, the core loss component of current remains in phase with? 📐

a) No‑load current
b) Primary supply voltage
c) Core flux
d) Primary induced voltage

Check Answer

Answer: b) Primary supply voltage
Explanation: Core loss current represents real power → in phase with supply voltage.

15The induced reactance of a transformer depends on? 📐

a) Electromotive force
b) Magnetomotive force
c) Magnetic flux
d) Leakage flux

Check Answer

Answer: d) Leakage flux
Explanation: Leakage reactance arises from leakage flux linking only one winding.

16Open circuit test performed on a transformer with? 🧪

a) Rated secondary terminal voltage
b) Rated transformer current
c) Direct current
d) High frequency supply

Check Answer

Answer: a) Rated secondary terminal voltage
Explanation: Conducted at rated voltage on LV side with secondary open to measure core losses.

17In transformer equivalent circuit, the core losses are represented as? 📊

a) Series resistance
b) Shunt resistance
c) Series inductive
d) Shunt inductive

Check Answer

Answer: b) Shunt resistance
Explanation: Core losses are modeled as a resistance in parallel with magnetizing branch.

18When a transformer is operating on no load, the primary applied voltage is approximately balanced by? ⚡

a) Primary induced emf
b) Secondary induced emf
c) Terminal voltage across secondary
d) Voltage drop across resistance/reactance

Check Answer

Answer: a) Primary induced emf
Explanation: Applied voltage ≈ induced emf in primary, since drops are negligible.

19Full load voltage regulation of a power transformer is zero when power factor of the load is near? 📈

a) Unity and lagging
b) Zero and leading
c) Zero and lagging
d) Unity and lagging

Check Answer

Answer: a) Unity and lagging
Explanation: At unity PF, voltage drop due to reactance cancels → regulation zero.

20In transformer, zero voltage regulation at full load is? 📈

a) Not possible
b) Possible at leading power factor load
c) Possible at unity power factor load
d) Possible at lagging power factor load

Check Answer

Answer: b) Possible at leading power factor load
Explanation: Leading PF load can cause terminal voltage rise, making regulation zero or negative.

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