Methodology

Primary sources, one link per number, a date on every row.

Where the data comes from

We read each maker’s own product pages, datasheets and brochures, annual reports, exchange filings and press releases, state economic-development releases, then named trade press (T&D World, Utility Dive, Transformers Magazine, Korea Economic Daily, DIGITIMES and others). Every record lists its sources with the date we accessed them, and every number in the table links to the source it came from. This dataset was compiled on 11 November 2026: 60 makers, each with at least three sourced fields.

How we verify

Each row shows the date we last checked it. A field is filled only when a source states it; when a maker does not publish a figure, the cell stays empty. Largest rating and Highest voltage are the maximum the maker publishes or has delivered, across all its transformer lines; Product range and Voltage classes say which line each figure belongs to. Regional ranges, group-history claims, base ratings and phase-shifter throughput are identified separately; a maximum in one column does not imply that every plant or product can supply it. The country lists cover verified locations and may be incomplete. A US or EU plant counts only when it is operating; planned plants carry their target date. Expansion amounts stay in their original currency; the dollar column holds only figures the source states in dollars.

Who is in, who is out

A maker is listed when it builds power or distribution transformers in its own plants and we could source at least three facts about it beyond its name. Makers we could not source that far are left out until we can. Brands already covered by a listed maker stay on that row: Kuhlman under Hitachi Energy, Crompton Greaves under CG Power, Southwest Electric under SGB-SMIT, and Power Partners, Pioneer and Jefferson Electric under ERMCO. Pauwels is a separate maker: its Belgian plant restarted under EIC in 2021 (company history).

Corrections

Vendors and readers can send corrections to hello@transformervendors.com with a public source. We update the row and its verified date. Featured placement is paid and labelled; it never changes a row’s data or its position in the sorted table.

Reuse

The dataset is free to reuse under CC BY 4.0 with a link to transformervendors.com. Download it as CSV or JSON.

Field definitions

21 fields

Segment: Power when the maker publishes power, GSU, HVDC, autotransformer or reactor products or a rating above 20 MVA; Distribution when it publishes distribution, pad-mount, pole-mount, network or dry-type products; both when it publishes each. Derived from Transformer types and Largest rating.
Transformer types: Product types the maker lists, separated by semicolons: power, GSU, autotransformer, HVDC, shunt reactor, substation, distribution, pad-mount, pole-mount, network, dry-type (cast resin, VPI), mobile, rectifier/industrial, renewable and data center lines.
Largest rating MVA: Largest verified published rating in the cited product or regional scope, in MVA. Product range identifies base, forced-cooling, phase-shifter throughput or group-history claims; these rating bases are not interchangeable. Planned future ranges are described separately.
Smallest rating kVA: Smallest published rating, in kVA. Shows how far down the distribution range a maker goes.
Product range: The kVA/MVA range as the maker states it, by product line.
Highest voltage kV: Highest voltage class the maker publishes or has delivered, in kV (AC system voltage; HVDC noted under Voltage classes).
Voltage classes: Voltage classes and BIL as the source states them, by product or plant.
Plants: Transformer manufacturing locations, city and country. Planned plants carry their target date. Location lists identify verified sites and may not cover every factory in a global group.
Plant countries: Countries with verified operating transformer manufacturing in the cited scope; not necessarily the complete global footprint. Component and service-only sites do not establish new-unit manufacturing.
US plant: Yes when an operating US transformer plant is verified; No when the source shows the maker's plants and none is in the US. Empty means not verified.
EU plant: Yes when an operating transformer plant in an EU-27 country is verified (the UK, Norway, Switzerland and Turkey do not count). Empty means not verified.
Capacity expansion: Announced transformer capacity expansions: amount in the original currency, place, announcement date, target date and output change. US and EU projects first.
Largest US/EU expansion $M: Largest single announced US or EU transformer capacity investment, in US$ millions, where the source states a dollar amount. Euro amounts stay in Capacity expansion unconverted.
Expansion region: Where the announced capacity expansions are: US, EU, both, or only elsewhere (Other).
Certifications and standards: Quality certifications, listings and design standards the source names (ISO 9001, IEEE C57, IEC 60076, EU Ecodesign Tier 2, utility approvals).
Data center offer: Yes when the maker markets transformers for data centers or has disclosed a data center transformer order. Empty means not found.
Data center product or order: The named data center line, or the disclosed order with value and date.
Parent or owner: Parent company or owner where the source states one.
HQ country: Country of the maker's headquarters.
HQ region: Region of the maker's headquarters.
Legacy brands and names: Sourced former names and acquired transformer businesses, retained on the current maker row to avoid duplicate supplier counts.