Products
Find a transformer supplier for your specification
Send one specification for a distribution, cast resin or oil immersed transformer. We put it to the manufacturers whose range covers its rating, voltage pair and standard, and the offers come back comparable.
- Rating
- kVA or MVAnever kW, because the unit carries apparent power
- Voltage pair
- primary and secondarythe network sets the primary at the connection point
- Construction
- liquid immersed or dry typeset by where the unit stands and whether oil is allowed there
- Standard
- IEC or IEEEset by the specification and the destination market
A transformer is specified in a fixed order. The load and the starting behaviour of its largest motor set the rating. The network sets the primary voltage, and the installation sets the secondary. Where the unit stands decides the construction. The enclosure, the tapping range, the fittings and the loss requirement follow from those three.
Capacity is stated in kVA or MVA because a transformer is rated for apparent power. Convert a load in kilowatts with its power factor before you compare it with a rating. Skip that step and the unit arrives undersized.
Transformer types
Distribution
Choosing the construction
| Construction | Typical placement | Why it is chosen |
|---|---|---|
| Liquid immersed, mineral oil | Outdoors, or in a dedicated transformer room | Usually lower cost per kVA, and suits outdoor installation |
| Liquid immersed, ester | Where fire safety or water protection governs | A higher fire point and better biodegradability than mineral oil |
| Dry type, cast resin | Indoors, including occupied buildings | No insulating liquid, so no liquid containment and a lower fire load |
| Pad mounted | Outdoors at ground level, on North American style networks | A tamper resistant cabinet that needs no separate enclosure |
Distribution transformer ratings
| Rating | Full load current at 400 V | Full load current at 433 V | Next step |
|---|---|---|---|
| 100 kVA | 144 A | 133 A | Request a quote |
| 160 kVA | 231 A | 213 A | Request a quote |
| 200 kVA | 289 A | 267 A | Request a quote |
| 250 kVA | 361 A | 333 A | Request a quote |
| 315 kVA | 455 A | 420 A | Request a quote |
| 400 kVA | 577 A | 533 A | Request a quote |
| 500 kVA | 722 A | 667 A | Request a quote |
| 630 kVA | 909 A | 840 A | Rating page |
| 800 kVA | 1155 A | 1067 A | Request a quote |
| 1000 kVA | 1443 A | 1333 A | Rating page |
| 1250 kVA | 1804 A | 1667 A | Request a quote |
| 1600 kVA | 2309 A | 2133 A | Rating page |
| 2000 kVA | 2887 A | 2667 A | Request a quote |
| 2500 kVA | 3608 A | 3333 A | Rating page |
Rated current at 400 and 433 V, three phase. The 630, 1000, 1600 and 2500 kVA rows open the engineering detail for that rating, and every other row opens a quote request with the rating filled in.
Where the destination changes the unit
In the UK, distribution network operators specify their ground and pole mounted units to ENA TS 35-1, now Issue 8 of March 2026. It covers two winding, liquid immersed, naturally cooled transformers from 25 to 2000 kVA at 7.2, 12, 24 and 36 kV. The loss ceilings of Regulation (EU) No 548/2014 still apply in Great Britain as assimilated law, with the EU's 2019 amendments already in the GB text. That includes the Tier 1 allowance for a one to one replacement where meeting Tier 2 would cost disproportionately.
In the Gulf the heat changes the design. IEC 60076-2 assumes a site of at most 40 °C, 30 °C in the hottest month and 20 °C over the year, and where the site exceeds any of these, every temperature rise limit falls by the excess. Kahramaa in Qatar specifies 55 °C maximum, 40 °C in the hottest month and 30 °C over the year, with a 50 °C design temperature. DEWA's standards in Dubai set 50 °C as the outdoor temperature all equipment must work in.
Documents and when they arrive
| Document | What it shows | When you receive it |
|---|---|---|
| Technical datasheet | Rating, voltages, losses, impedance, dimensions and weight of the unit offered | With the quotation |
| Outline drawing | Footprint, lifting points and cable connection positions | With the quotation or at order |
| Routine test report | The tests on the individual unit to its standard | Before shipment |
| Type test report | The design has passed the type tests of its standard | Referenced with the quotation, where a type test exists for the design |
| Rating plate details | The declared values carried on the unit itself | With the delivered unit |
| Declaration of conformity | Conformity with the legislation of the destination market | With the delivered unit, where the destination market requires one |
| Operating and maintenance manual | Installation, operation and maintenance instructions | With the delivered unit |
The destination market, the standard and the manufacturer decide which documents apply. The quotation lists them for the unit offered.
Getting a transformer to site
A delivery date means little until the site is ready for the unit. Its outline drawing gives the dimensions and the mass, and those decide the vehicle, the crane and the route to the plinth. Ask for the drawing early, because a change of rating or construction changes all three.
A liquid immersed unit normally travels filled, so the transport rules for its liquid apply on the road and the handling plan applies on arrival. A border crossing adds customs documents, and where the destination has its own conformity or efficiency rules, the paperwork follows the destination rather than the country of manufacture.
Each quotation states the delivery basis the manufacturer gave for the unit offered and the date it was given, because order books move.
What every transformer request needs
- Rated power in kVA, or the connected load and the largest motor if the rating is not fixed yet
- Primary and secondary voltage, and the tapping range if the network operator sets one
- Phase, frequency and the vector group, or the earthing arrangement it has to suit
- Construction: liquid immersed or dry type, and whether oil is acceptable where the unit will stand
- Indoor or outdoor, ambient temperature, altitude and any corrosive or dusty exposure
- The standard and the loss requirement the destination market applies
- Quantity, destination and the date the equipment has to be on site
- Whether surplus or refurbished units are acceptable, or new only
Specification template
Fill it in on screen or by hand, then upload it with your request.
Questions buyers ask
Which documents come with a transformer?
The datasheet and outline drawing with the quotation, the routine test report before shipment, and the rating plate, declaration and manual with the unit. The table above sets out when each arrives.
Do you publish prices?
No. A transformer price moves with rating, loss level, voltage pair, tapping, enclosure, standard and delivery basis. Every quotation is priced for the specification it states.
Can you source to a North American specification as well as IEC?
Send it as written. We put an IEEE or IEC specification to the manufacturers whose range covers that standard, and the reply says whether a unit built to it can be supplied to your destination.