Transformer no-load and load loss — quick reference
Enter the load and the transformer data. The engine returns the no-load loss P0, the load loss Pk at the actual load, the total loss, the no-load share of the annual loss, the load-zone judgement, the temperature rise and the annual energy loss. Anything the input cannot support is shown as not available - never as zero.
Sample case pre-filled: transformer 1000 kVA / Dyn11 with GB 20052-2020 grade-1 typical P0/Pk, load 600 kW at cos phi = 0.90, ambient 40 C, 8760 operating hours per year with 4000 equivalent full-load hours. Overwrite the fields with your own nameplate data - every number below is computed by the engine, not by this page.
RequiredRecommendedLeft bar: blue = required, gold = recommended. Optional and advanced fields are collapsed by default.
P0 and Pk are nameplate values. Enter them and the engine uses them (source: user). Leave them empty and the engine substitutes the GB 20052-2020 grade-1 typical values and marks the result as typical - this page shows that mark next to the number instead of hiding it. Leave the energy price empty and the annual cost is shown as not available.
Not calculated yet - fill in the input data and press Calculate.
Not available: the engine does not output a numeric transformer efficiency for this study, and this page does not run a second calculation of its own. Efficiency is therefore expressed through the engine outputs that do exist: the load-zone judgement, the no-load share of the annual energy loss and the loss figures above.
Not available: this page models the transformer only. Line and cable loss need a complete topology with outgoing cables - open the scheme-based Losses column for those.
P0 and Pk: the nameplate values if you enter them, otherwise the GB 20052-2020 energy-efficiency grade-1 typical table interpolated by rated capacity (single source: engines/params.js P0PK_TAB / resolveXfLoss).
P_loss = P0 + Pk x (S/Sn)^2; annual energy loss = P0 x t + Pk x (S/Sn)^2 x t_eq, with S/Sn taken from the actual load and power factor.
No-load reactive loss q0 = i0 % x Sn; load reactive loss qk = uk % x Sn x (S/Sn)^2. Temperature rise follows IEC 60076-7 (55 K top-oil and 80 K hot-spot at rated load, exponential model).
This page performs no calculation of its own. Every number comes from the engine module studies2.js losses() through the standard design endpoint; that study reads the single P0/Pk source in engines/params.js. The page only maps your input to the request and displays what comes back.
Sample case: 1000 kVA transformer with the GB 20052-2020 grade-1 typical P0 = 1.15 kW and Pk = 9.00 kW, load 600 kW at cos phi = 0.90, so the load rate is (600 / 0.90) / 1000 = 0.667 pu and P_loss = 1.15 + 9.00 x 0.667^2 = 5.15 kW.
Definitions, units and why the number matters for selection and quotation. Searchable, grouped by topic, collapsed by default.
Every ? mark on this page opens the same explanation in place — no page change.
5 term(s) shown of 5
No-load loss of a transformer: the power absorbed at rated voltage and rated frequency with the secondary winding open (IEC 60076-1). It is essentially the core (hysteresis + eddy) loss.
Why it matters: It runs continuously — about 8 760 h a year — so it dominates the lifetime energy bill. Tenders commonly capitalise it at a $/W figure, which means a lower P0 can justify a higher purchase price.
Load loss (short-circuit loss) of a transformer: the power absorbed at rated current with the secondary short-circuited, corrected to the reference temperature (IEC 60076-1). It includes the I²R loss plus stray and winding eddy losses.
Why it matters: It grows with the square of the load and is the basis of efficiency guarantees and of any loss-capitalisation clause. Pk and uk% come from the same test, so a datasheet giving one without the other is incomplete.
Short-circuit impedance voltage of a transformer: the primary voltage, in percent of rated voltage, that drives rated current through the short-circuited secondary winding (IEC 60076-1).
Why it matters: It fixes the LV fault level (approximately I″k ≈ In / uk) and at the same time the voltage drop under load. This is a real quotation trade-off: a larger uk lowers the fault level (cheaper switchgear downstream) but increases voltage drop and losses. Always quote uk together with the transformer rating.
Power factor cos φ: the ratio of active power to apparent power (displacement factor between voltage and current), with the distortion factor included when the current is distorted.
Why it matters: It sets the kVA that the transformer, generator or supply contract must provide for a given kW, and it is contractual: a low power factor triggers penalty charges or a mandatory compensation bank. It is therefore both a design input and a line in the price.
Loading: the current (or power) carried by a branch expressed as a percentage of its rated capacity.
Why it matters: It is the acceptance number for cables and transformers. Above 100 % the element will trip or have to be derated, and the margin left at the design case is exactly what the customer is paying for — so it must be shown with the assumption (load factor, ambient temperature) that produced it.
This page is a preliminary engineering estimate for one transformer. Network line/cable loss, loss allocation across the whole diagram and the full load flow need a complete topology - open the scheme-based Losses column for those.