The permanent magnet variable-speed generator is directly coupled to the turbine. It has an external rotor. The stator windings are assembled on a fixed shaft in central position.
They are ventilated and refrigerated by contact with the water flowing around the bulb and by fans.
The rotor is equipped with permanent magnets, and is solid with the turbine runner. The magnets are assembled at the stator periphery.
The generator speed may vary according to the instantaneously-measured net head. It will thus enable to optimize the turbine efficiency, by placing it in its best efficiency area whatever the observed head. The VLH will thus keep its nominal efficiency down to 40% of the nominal head, which provides it with a yearly production capacity equivalent to that of a conventional double-adjustment Kaplan turbine(refer to speed variation).
The generator is pressurized to a relative value corresponding to the measured water pressure plus from 0.2 to 0.3 bar. Thereby, there will be no flooding of the stator due to possible lacks of tightness. This feature also helps drying the ambient air.
It is entirely assembled and tested in the factory, and mounted on site inside of the distributor.