The DF generator (DFIG) is an asynchronous wound rotor slip ring machine where the rotor windings are connected to a small converter via slip rings and brushes. The generator feeds power both from the stator and also from the rotor. A small (1/3 Pn) converter can be used, because a speed range of +/- 30 % is sufficient for wind turbine applications. The converter enables control of the generator speed, power and power factor, thus giving a wider speed range and improving the energy yield and ability to feed reactive power to support the grid. The DF concept therefore represents an economical way of achieving semi-variable speed operation and satisfying basic grid code requirements.

The proven ABB family of 1.5 – 3.6 MW DF generators has been designed to fit most turbines used today. The standard modular structure - with both air or water cooling - can be modified for different turbine interface connections. The generator features a rigid rotor design for higher overspeed and voltage peak withstand to fit most converter designs used in the markets. The new advanced ABB slip ring series is designed for long service life and easy maintenance.

Customer specific generators are available by request from 500 kW up to 6 MW.