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The VIRYA-3.3Swindmill is designed especially for manufacture in developing countries. This windmill is designed to be coupled to the 3-phase asynchronous motor of a small centrifugal pump. The pump motor should have a nominal power of 0.55 kW and should be loaded up to maximal a factor 0.8 of the nominal power. The rotor of the VIRYA-3.3Shas three curved blades which are made from 2.5 mm galvanised steelsheet. 12 blades can be made from a standard sheet size 1.25 * 2.5 m with almost no material waste. The blades are bolted to a welded spoke assembly which is bolted to the hub. A special blade press is designed for cambering the blades. This windmill uses a generator whichis made ofa 6-pole asynchronous motor frame size 112. The motor is modified by a 34-pole permanent magnet armature with 51 neodymium magnets size 40 * 10 * 5 mm. The original motor shaft isused. The windmill rotor is mounted direct ly to the generator shaft. The generator stator is provided with a special 3-phase winding which has 18 single coils. The generator can probably be used as a brake by short-circuiting the generator winding over a resistance. A frequency controlled 3-phase switch is mounted in between the generator and the pump motor. This switch connects the motor and the generator at a frequency of about 52 Hz and disconnects motor and generator at a frequency of about 35 Hz. This facilitates starting of the rotor and gives a pulsating water flow even at low wind speeds. This switch also allows the use of a positive displacement pump or even an other load which accepts a varying frequency, like a cornmill.The windmill is provided with the so called “hinged side vane safetysystem” to limit rotor rpm and thrust at high wind speeds. The rotor axis is offset from the tower axis. The vane juts out along the rotor and the vane blade is connected to the vane arm using hinges. At low wind speeds, the vane blade hangs in almost vertical position and the rotor is perpendicular to the wind. At windspeeds higher than about 5 m/sthe rotor starts to turn gradually out of the wind. The rotor is about 35° turned out of the windat a wind speed of 11 m/s. At very high wind speeds the rotor turns out of the wind by about 75° and the vane blade is in almost horizontal position. The behaviour of this system is very stable and the rotor speed is well controlled.Detailed description of this safety system is given in public report KD223 for a rotor with cambered steel blades. The free standing tubular tower consists of three,3metrelong sections which are bolted together. The lowest section is clamped in between two heavy foundation stripswhich are poured into concrete. The tower can hinge at the tower foot by using only two of the eight foundation bolts, an auxiliary towerand a winch. A prototype of the VIRYA-3.3Shas not yet been built and tested but an Indian company is interested to build it and will first test a prototype of the generator. A prerequisite for manufacture of this windmill in developing countries is that one is able to import some of the materials and standard parts. Kragten Design cannot supply materials and parts such as bearings, generators, magnets, electronics and pumps. The required workshop skills are sawing, drilling, turning, milling and welding.


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