M WR
Wound-rotor induction motor
A wound-rotor induction motor includes a rotor winding arrangement with documented external connections.
SLD / Schematic
Symbols · WTG T2
Variable-slip wind turbine generator (Type 2)
A wind turbine using a wound-rotor induction generator with controlled external rotor resistance to widen the slip range.
In plain English
What does Variable-slip wind turbine generator (Type 2) mean?
A Type 2 wind turbine uses a wound-rotor induction generator whose rotor circuit is connected to a variable resistance, usually switched by power electronics mounted on the rotor. Raising the rotor resistance lets the slip increase to around ten per cent, which softens torque peaks from gusts while the stator stays connected directly to the network.
A simple example
Drawings show the generator circle with rotor slip-ring or rotor-winding marks and a resistor element with a variable arrow attached to the rotor side. The stator side follows the same path as a Type 1 machine: soft starter, capacitor compensation and step-up transformer.
What the drawings help you do
Energy dissipated in the rotor resistance is lost as heat, so the symbol says nothing about efficiency or about any capability to deliver reactive power. Fault ride-through behaviour and resistor ratings must be read from the turbine model data.
This particular reference
A wind turbine using a wound-rotor induction generator with controlled external rotor resistance to widen the slip range. A Type 2 turbine dissipates rotor energy in resistance; a doubly-fed generator returns rotor power to the network through a converter.
- Winding
- A coil of conductor inside an electrical machine or transformer.
- Rating
- A value stating the conditions for which equipment is specified.
- Schematic
- A drawing showing function and connections rather than physical appearance.
Read the source: AutoCAD Electrical: Power station and substation concepts · Resistors and heater-element symbols
SLD / Schematic · WTG T2
What it represents
A Type 2 wind turbine uses a wound-rotor induction generator whose rotor circuit is connected to a variable resistance, usually switched by power electronics mounted on the rotor. Raising the rotor resistance lets the slip increase to around ten per cent, which softens torque peaks from gusts while the stator stays connected directly to the network.
Drawings show the generator circle with rotor slip-ring or rotor-winding marks and a resistor element with a variable arrow attached to the rotor side. The stator side follows the same path as a Type 1 machine: soft starter, capacitor compensation and step-up transformer.
Energy dissipated in the rotor resistance is lost as heat, so the symbol says nothing about efficiency or about any capability to deliver reactive power. Fault ride-through behaviour and resistor ratings must be read from the turbine model data.
How to read it
- The variable resistor on the rotor side is a slip control element, not a braking resistor or a load.
- Stator-side compensation capacitors are still normally present.
Information to show or reference
- State rotor resistance control range.
- Show stator connection and compensation.
- Reference turbine model data for dynamic studies.
A distinction that matters
A Type 2 turbine dissipates rotor energy in resistance; a doubly-fed generator returns rotor power to the network through a converter.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
AutoCAD Electrical: Power station and substation concepts
Wind station representation used as site-level context.
Resistors and heater-element symbols
Public variable-resistor symbol context for the rotor resistance element.
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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Fixed-speed wind turbine generator (Type 1)
A wind turbine whose squirrel-cage induction generator connects to the network directly, running at nearly constant speed.
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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.
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Variable resistor
A variable resistor provides a documented adjustable resistance in a circuit path.
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