Learn Transformer Design
Start with the 26-chapter design course — chapters 1–2 are free — then follow the book-matched path through operations, diagnostics, manufacturing, components, protection, specials, site work, loading, repair, standards, asset management, the handbook and HVDC.
Open the design course → or follow the Design Engineer Track
Design Engineer Track
Four levels, ~400 guided hours and five capstone projects. Level 1 is free to start. Full Levels 1–4 need 12 months access.
Start the track →Design Engineer Track — 12 months access
One payment unlocks the entire learning platform:
- All four levels — Foundations, Distribution, Power Transformer and Specials & Mastery
- All courses & tools — design course, tutorial, academy, 3D models, formulas and design calculators
- Published model answers — the model answer for all five design projects. Capstones are not personally reviewed
- Written record — a record of every capstone you complete (currently stored on your device; account-synced progress is being added)
🏢 A whole team on one plan?
Engineering Team is a self-serve payment for 12 months of access. There is no live class and no custom training.
⚡ Transformer Grid Lab
Interactive 3D power system journey from 21 kV generator → 400 kV GSU → 220 kV autotransformer → 33/11 kV substations → 415 V consumer loads with live I²R loss calculations & OLTC regulation.
Launch Grid Lab →🧩 Component 3D Explorer
Rotate, zoom and explode a transformer in 3D — oil-immersed and cast-resin modes, toggle components, and click any part to learn what it does.
Explore 3D models →🧰 Course Tools Hub
One map of every interactive model and calculator that belongs with the design course — open a tool, then come back to the chapter that uses it.
Open tools hub →More Courses & Tools
Interactive learning and engineering tools — included with 12 months access.
Power Transformer 3D
Explore a 100 MVA 132/33 kV power transformer in interactive 3D.
Core & Coil Assembly 3D
See how the core is built and the coils are assembled, step by step.
TX Calculation
Live IEC 60076 sizing suite — distribution / power / cast-resin, three modes.
Construction Guide
From core to customer — a complete construction walkthrough.
Country-Based Designer
Design a transformer to a chosen country's grid and standards.
500 MVA Transformer 3D
A 400/220 kV giant in interactive 3D — radiators, conservator and OLTC.
OLTC 3D Cutaway
See inside an on-load tap-changer — diverter, selector and drive in 3D.
Condenser Bushing 3D
RIP and OIP bushings in an interactive 3D cutaway.
Core Topology 3D
3-limb vs 5-limb vs shell-form cores, compared in interactive 3D.
Industry events
OEM, supplier and institute events — live sessions, recurring series and on-demand replays.
Events calendar
In-person exhibitions and conferences worldwide, with map pins for upcoming editions.
The book-matched path
Volumes 0–19 in series order. Each card is original course copy that points to the matching volume — not a reprint of the book.
V0–V2 Design
Fundamentals (planned), Volume 1 Edition 1, and Volume 2 Edition 1 — beside the 26-chapter design core.
V3–V5 Test, diagnostics, failures
Factory testing and diagnostics (both planned / being prepared) plus forensic investigation of a failed unit.
V6–V10 Works, materials, losses, withstand
Manufacturing, insulation, components, loss economics and short-circuit strength.
V11–V16 Network, specials, site, loading, repair, standards
Protection, special transformers, site work, loading, repair and quality assurance.
V17–V19 Fleet, handbook, HVDC
Utility asset management, the question-indexed handbook, and the converter grid the installed fleet was not specified for.
The Design Curriculum
The 26-chapter design core, in the order a real design is built. Each lesson links to its matching volume. This week's spotlight is highlighted.
1 Fundamentals
How a transformer works — mutual induction, the EMF equation, ideal vs real behaviour, and the rating inputs (kVA, voltage ratio, frequency, phases) that drive everything downstream.
2 Classification & Specification
Power vs distribution, core-type vs shell-type, cooling classes (ONAN/ONAF), vector group, impedance, tap range and the standards (IEC 60076 / ANSI C57) the customer specifies.
3 Core Design & CRGO
Choosing core area and flux density, CRGO grades and stacking factor, and how silicon steel cuts hysteresis and eddy losses — setting iron weight and no-load loss.
4 Windings & Current Density
Conductor sizing from current density, LV-over-core then HV arrangement, layer/disc/helical windings, and the window-area check that confirms it all fits.
5 Insulation System
Turn, layer and major insulation; pressboard and paper (IEC 60641); clearances and creepage; oil as a dielectric — the discipline that decides reliability and life.
6 Thermal & Cooling Design
Temperature rise, radiators and fans, ONAN/ONAF/OFAF classes, oil flow and hot-spot control — turning loss watts into a safe operating temperature.
7 Tank & Accessories
Tank, conservator, bushings, tap-changer (OLTC/DETC), Buchholz, breather, protection and monitoring — the hardware around the active part.
8 Dry-Type & Cast Resin
Cast-resin and VPI dry-type transformers — where they win, their thermal classes, and design differences from oil-immersed units.
9 Worked Design Example
A complete 1000 kVA design worked end-to-end — from spec through core, turns, windings and window check to losses, the way a real designer builds it.
10 Losses, Impedance & Efficiency
No-load and load loss, leakage reactance and percent impedance, efficiency and voltage regulation — the numbers the customer guarantees.
11 Testing & Type Tests
Routine, type and special tests — ratio, winding resistance, no-load and load loss, impedance, insulation, impulse and temperature-rise — verifying against IEC 60076.
12 Standards
The IEC 60076 family, ANSI/IEEE C57, and the component standards for bushings, tap-changers, oil and pressboard you design to.
13 Vector Groups
Dyn11, Ynd1 and the rest — phase displacement, why it matters for paralleling, and how the connection is built in the windings.
14 Inrush
Magnetising inrush current — why it happens at switch-on, how large it gets, and how protection is set so it doesn't false-trip.
15 Special Types
Autotransformers, converter and furnace transformers, earthing transformers and other specials — what changes in the design.
16 Site & Life
Installation, commissioning, oil management, condition monitoring and end-of-life — getting the full service life out of the unit.
17 Protection
Differential, REF, overcurrent, Buchholz and pressure-relief protection — the relays and devices that keep a transformer (and the grid) safe.
18 Procurement & Tendering
Reading a tender spec, building a compliant offer, guarantees and penalties, FAT/SAT and how buyers actually evaluate transformer bids.
19 Glossary & Self-Test
Key terms in one place plus a quick self-test to check your understanding of the whole course.
20 After-Sales & Service
Warranty, spares, retrofits, oil treatment and field service — the support a transformer needs across decades in operation.
21 Bushings
OIP/RIP/RIS types, condenser grading, test taps, creepage & pollution class, and why bushings cause most transformer fires — with the 3D condenser-bushing cutaway.
22 Tap-Changers
OLTC vs DETC, diverter/selector/change-over, resistor vs vacuum switching, AVR control and DGA of the diverter — with the 3D OLTC cutaway.
23 Impulse & Stress Control
How a winding sees a steep surge: initial vs final distribution, the α constant, and static rings, shields & interleaving that protect the line-end turns.
24 Fire, Containment & Environment
Pressure/arc protection, nitrogen-injection & deluge, bunds and oil-water separation, ester fire safety and sustainability — the envelope around the transformer.
25 Worked 500 MVA Design
An EHV 400/220 kV worked design — currents, volts-per-turn, 5-limb core, impedance, impulse grading and ONAN/ONAF/ODAF cooling — behind the 500 MVA 3D model.
26 Engineering Data Appendix
Reference tables designers keep open beside the calculator — ratings, insulation levels, impedance bands, temperature-rise limits and insulating liquids.
Self-test and first-pass sizing
The knowledge check and sizing engine below run in the browser. The full formula set and design workspace ship with 12-month access.
Start free chapters → See plansTransformer Engineering Self-Test
Test your mastery of core electromagnetics, vector groups, thermal aging, and short-circuit forces.
⚡ Sizing Engine
Compute volts-per-turn, net core cross-section, turn counts, and line current densities.
Validation example
Inputs. 3-phase, 1,000 kVA, 11 kV / 0.433 kV, 50 Hz, peak flux 1.65 T, current density 2.8 A/mm², K = 0.45.
Expected. Volts per turn 14.23 V, net core area 388 cm², HV turns 446, LV turns 18, HV line current 52.5 A, LV line current 1,333 A, HV conductor 18.7 mm², LV conductor 476 mm².
References. Line current is I = S / (√3 · U) for three phases, the rated-current relation in IEC 60076-1, with U in volts. Phase voltage for a star winding is the line voltage divided by √3. Turns are that phase voltage divided by volts per turn. Net core area uses the sinusoidal EMF equation E = 4.44 · f · N · B · A, rearranged as A = Eₜ / (4.44 · f · B). Conductor area is current divided by current density. K√kVA is this page’s empirical volts-per-turn start, not an IEC constant. Star connection is assumed for the three-phase case.
Engineering course authored for TransformerPath. The calculator gives a first-pass estimate using simplified formulas — always design to the applicable IEC 60076 / ANSI C57 standard.
One tap tells us what to improve. Optional email for a follow-up.