Doubly fed electric machine
electric motors or electric generators, where both the field magnet windings and armature windings are separately connected to equipment outside the machine
A doubly fed electric machines, doubly fed induction generator (DFIG), or slip-ring generator is an electric motor or electric generator where both the field magnet windings and armature windings are separately connected to equipment outside the machine.
By feeding adjustable-frequency AC power to the field windings, the magnetic field can be made to rotate, allowing variation in motor or generator speed. This is useful, for instance, for generators used in wind turbines. Doubly fed electric machines are also used in variable-speed pumped-storage hydropower plants. Additionally, DFIG-based wind turbines offer the ability to control active and reactive power.
Introduction
Doubly fed electrical generators are similar to AC electrical generators, but have additional features which allow them to run at speeds slightly above or below their natural synchronous speed. This is useful for large variable speed wind turbines, because wind speed can change suddenly. When a gust of wind hits a wind turbine, the blades try to speed up, but a synchronous generator is locked to the speed of the power grid and cannot speed up. So large forces are developed in the hub, gearbox, and generator as the power grid pushes back. This causes wear and damage to the mechanism.
This brief starts where responsible research should: with the source description of “Doubly fed electric machine” as electric motors or electric generators, where both the field magnet windings and armature windings are separately connected to equipment outside the machine. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the general reference register because the source frames it as electric motors or electric generators, where both the field magnet windings and armature windings are separately connected to equipment outside the machine. Its deeper value depends on whether names, dates, institutions and citations support that framing.
Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Aug 14, 2026. The linked authority identifier is Q1420518. None of the 0 selected statements returned an explicit reference.
Overview language is designed for orientation and should not be treated as a substitute for the evidence cited beneath it. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Doubly fed electric machine” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.