M WR
Wound-rotor induction motor
A wound-rotor induction motor includes a rotor winding arrangement with documented external connections.
SLD / Schematic
Symbols · DFIG
Doubly-fed induction generator
A wound-rotor induction generator with the stator on the network and the rotor fed through a back-to-back converter sized for slip power.
In plain English
What does Doubly-fed induction generator mean?
A doubly-fed induction generator has its stator connected directly to the turbine transformer while the rotor windings, reached through slip rings, connect to a back-to-back AC/DC/AC converter. The converter injects rotor currents at slip frequency, allowing variable speed of roughly plus or minus thirty per cent around synchronous speed and independent control of active and reactive power.
A simple example
On a single-line diagram the generator circle shows two connections: the stator branch to the main breaker and the rotor branch to a pair of converter blocks joined by a DC link. A crowbar or DC chopper is often shown on the rotor converter for fault protection, and a line filter or reactor sits on the grid-side converter.
What the drawings help you do
Because the converter only carries slip power, typically a quarter to a third of the turbine rating, the symbol does not imply full decoupling from the network. Short-circuit contribution, crowbar operation and ride-through capability depend on control settings that the diagram does not show.
This particular reference
A wound-rotor induction generator with the stator on the network and the rotor fed through a back-to-back converter sized for slip power. A DFIG converter handles only rotor slip power; a full-converter turbine passes all generator output through the converter.
- DC
- Direct current: electricity flowing in one direction.
- AC
- Alternating current: electricity whose direction changes periodically.
- Winding
- A coil of conductor inside an electrical machine or transformer.
Read the source: Bidirectional three-/single-phase AC/DC PFC and inverter application note · Generator symbol variants
SLD / Schematic · DFIG
What it represents
A doubly-fed induction generator has its stator connected directly to the turbine transformer while the rotor windings, reached through slip rings, connect to a back-to-back AC/DC/AC converter. The converter injects rotor currents at slip frequency, allowing variable speed of roughly plus or minus thirty per cent around synchronous speed and independent control of active and reactive power.
On a single-line diagram the generator circle shows two connections: the stator branch to the main breaker and the rotor branch to a pair of converter blocks joined by a DC link. A crowbar or DC chopper is often shown on the rotor converter for fault protection, and a line filter or reactor sits on the grid-side converter.
Because the converter only carries slip power, typically a quarter to a third of the turbine rating, the symbol does not imply full decoupling from the network. Short-circuit contribution, crowbar operation and ride-through capability depend on control settings that the diagram does not show.
How to read it
- Follow both the stator and rotor paths; they usually join again at the turbine transformer low-voltage side.
- Identify the crowbar or chopper, since it changes fault behaviour.
Information to show or reference
- State stator rating and rotor converter rating separately.
- Show crowbar, chopper and line filter if fitted.
- Reference grid-code ride-through data.
A distinction that matters
A DFIG converter handles only rotor slip power; a full-converter turbine passes all generator output through the converter.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Bidirectional three-/single-phase AC/DC PFC and inverter application note
Public bidirectional AC/DC converter context relevant to the rotor-side back-to-back stage.
Generator symbol variants
Public generator symbol family context; the DFIG artwork is independently drawn.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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