Transformer simulation, from losses to hotspot temperature
Find out where a transformer’s losses arise, how hot the windings run at full load and overload, and which core, winding or cooling changes bring the hotspot down, before the first unit is wound.
Transformer temperature rise is often judged on the average winding temperature, yet insulation ages fastest at the hottest spot. Leakage flux at the ends of the windings induces eddy currents in the conductors, the tank and the clamping structure, so the worst losses and the highest temperatures can sit well away from where a design-sheet estimate places them.
More about transformer simulation
Transformer simulation solves the magnetic field through the core and windings to give core loss, winding loss including eddy current effects, and stray loss in the structural steel. Those losses are then applied as heat sources in a thermal model of the transformer and its cooling, so the predicted hotspot follows from the real loss distribution rather than an assumed one. The same field solution gives the electromagnetic forces on the windings when a short-circuit current flows.
A three-dimensional model of core, windings and tank lets alternative duct spacings, core steels or radiator arrangements be compared on equal terms. SixGate™’s engineers design as well as analyse, so what comes back is a set of changes to winding layout, shielding or cooling that can go straight into the detailed design, drawings and production of the next unit.
Typical products: distribution and dry-type transformers, cast resin units, traction and rectifier transformers, reactors and high-frequency magnetics for power electronics.
What a transformer study tells you
Where is the hotspot, and how hot is it?
Winding hotspot temperature and its position at rated load, overload and your worst-case ambient, set against the temperature limit of the insulation system.
How are the losses split?
Core loss, winding I²R loss, eddy current loss, and stray loss in the tank and clamps, each located in the geometry so you know which one to attack.
Is the cooling doing its job?
Oil or air velocities through the cooling ducts, radiators and fans, showing starved ducts and places where the flow bypasses the windings.
Will the windings withstand a short circuit?
Radial and axial electromagnetic forces on the windings at peak fault current, ready for a structural assessment of the spacers, supports and clamping.
Is stray flux heating the structure?
Leakage flux entering the tank walls, clamping frames and bushing plates, and whether magnetic shunts, conductive shields or non-magnetic inserts would reduce the heating.
What we model
Magnetic field and core loss
Flux density through the limbs, yokes and corners, with core loss taken from the steel’s loss data at your operating flux density and frequency.
Winding losses
Resistive loss plus eddy current loss from leakage flux, including proximity effects at higher frequencies.
Stray losses in structures
Eddy current heating in the tank, clamps, flitch plates and bushing plates, with shunts and shields compared directly.
Oil-filled cooling
Natural and forced oil circulation through windings, ducts and radiators, covering ONAN, ONAF and forced-oil arrangements.
Dry-type and cast resin units
Air cooling through and around the coils, including the enclosure, its ventilation openings and any fans.
Short-circuit forces
Electromagnetic forces on the windings under fault current, with the loads from the field study applied to the structural model of supports and clamping.
Coupled electromagnetic-thermal
Losses applied as heat sources in the thermal model, with conductor resistance taken at operating temperature rather than cold.
Before you start
What to send us
- CAD or dimensioned drawings of core, windings, tank and clamping (STEP or native)
- Rating, voltage ratio, frequency and winding connections
- Winding details: turns, conductor size, strands and transposition
- Core steel grade, or its loss and B-H data
- Cooling arrangement, with duct, radiator or fan details and oil or resin properties
- Load cases: rated, overload, maximum ambient and short-circuit current
Can you model a transformer without full 3D CAD?
Yes. Dimensioned drawings of the core, windings and tank are enough for us to build the model, and we can produce the CAD as part of the study.
Can you simulate oil flow, or only temperature?
Both. Oil velocity through each duct is solved together with the heat transfer, which is how starved ducts and local hotspots show up.
Can you help with a stray loss problem on an existing design?
Yes. With the design data and the losses you have measured or expect, we can locate where stray flux is heating structural parts and compare shunts, shields or non-magnetic sections to reduce it.
Does simulation replace the temperature rise test?
No. Type tests remain the evidence your customer or standard requires. Simulation means you go into that test with a design whose temperatures you already understand.
Send us your transformer
