Qwestrum Engineering360 · Electrical & Electronics · Electrical Machines – I
How does a transformer work?
A transformer transfers AC power between circuits by electromagnetic induction at nearly constant frequency — voltage changes but power (ideally) is conserved: V1/V2 = N1/N2.
Exam tip: keep SI units consistent end-to-end, write the governing relation symbolically before substituting, and sanity-check magnitude and sign.
Quick revision
Skim these first — then read the full notes below.
- Works on AC only — mutual flux links primary and secondary
- EMF equation: E = 4.44fNφm
- Core losses (hysteresis + eddy) and copper losses
- Efficiency maximum when variable loss = constant loss
Exams & GATE
- 1GATE EE: equivalent circuit, open/short circuit tests, efficiency calculation.
- 2Nagrath & Kothari transformer chapter is sufficient.
Interview prep
Utility and panel builder interviews: transformer cooling (ONAN, ONAF), tap changer purpose, % impedance.
📖 Standard books (India)
Electrical Machines — Nagrath & Kothari
Read: Ch. 1–3
Transformers, DC machines, and induction motors
Understand the concept
Transformers are everywhere in Indian grids — from 400 kV substations to the 11 kV/415 V distribution transformers on every street.
Schematic diagram for study — aligned with standard B.Tech / GATE syllabus.
Single-phase transformer. V₁/V₂ = N₁/N₂ = I₂/I₁ (ideal). Equivalent circuit from OC and SC tests.Explore related topics
See real electrical & electronics careers
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