Prime-mover dynamo plants – Fluid-current motors – Wind
Patent
1992-05-06
1994-05-24
Pellinen, A. D.
Prime-mover dynamo plants
Fluid-current motors
Wind
F03D 900, H02K 718, H02K 4102
Patent
active
053151593
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a wind turbine for generating electrical energy by means of wind energy, which wind turbine comprises a turbine rotor which is to be mounted on a mast and is rotatable about a rotor shaft with one or more rotor blades, and a generator equipped with rotor and stator. Such a wind turbine is known in practice, for example from the Holec brochure "Wind turbine type WPS 30-3 for wind farm application", 1987.
For various reasons, including environmental aspects and shortage of energy, wind energy has already been used for a long time now for the supply of electricity in thinly populated areas. The wind turbines used here are being built in increasingly large numbers and sizes. A problem here is the low energy content of the medium air. The power output of a wind turbine is in fact directly dependent on the wind-catching surface of the turbine rotor equipped with one or more blades, so that large turbine rotors have to be used. As a result of the high peripheral speed of the ends of such large turbine rotors, the maximum achievable speed of rotation is limited, inter alia, by material aspects such as strength, material fatigue etc., the shape and number of the rotor blades, and environmental aspects such as noise nuisance. This means that the available speed of ratation on the turbine rotor will be a factor of 10 to 30 times lower than in the case of a conventional generator.
Since the power output of a generator is directly proportional to the speed, measures have to be taken to increase the speed or to adapt the generator to the low speed. This adversely affects the price per unit of power supplied. As a general rule, it can be said that the price per unit of power supplied is related to the weight of the plant, i.e. the heavier the plant, the higher the price of the power supplied. In order, nevertheless, to be able to work with conventional high-speed generators and to obtain a reasonable power output, in the state of the art many wind turbines are coupled by means of intermediate shafts, geared transmissions, couplings and brakes to these high-speed generators. In this way the low speed of rotation of the wind turbine is adapted by means of a mechanical gear or up-converter to the much higher speed of rotation of the standard three-phase generator. The above-mentioned conversion components are generally accommodated in a heavy and bulky gondola on the top of the mast for the wind turbines.
In particular in the case of wind turbines for greater outputs, for example above 100 kW, it has been found in practice that in operation they are highly susceptible to serious defects and require frequent maintenance. The susceptibility to faults of the above-mentioned conversion train (turbine rotor, shafts, intermediate shafts, couplings, gearbox, brake and generator) has become increasingly clear. The complexity of the conversion train makes this train sensitive to the difficult conditions of wind turbine operation, such as vibrations, resonances, great force and couple variations.
In order still to achieve the same power output at low speeds of wind turbines without conversion by means of a whole conversion train, the generator can also be adapted. This can be achieved by, for example, increasing the number of poles in the generator. This leads in turn to an increase in the dimensions of the generator. German patent publications DE-3629872 A1 and DE-3638129 A1 give examples of a wind turbine in which a generator with a large number of poles and therefore large diameter is integrated in the tower structure. This generator is driven directly by the wind turbine in this case. The generator concerned here is of the synchronous type with permanent magnets, and built in the conventional manner as a round, rotationally symmetrical ring machine. Such a machine has, however, as disadvantages the use of expensive magnets and the large diameter of the stator on which, as a result of the low angular speed of the wind turbine with high pole number, they have to be designed. As a result of the large diamete
REFERENCES:
Sears, Zemansky & Young, College Physics, 1985, pp. 606-607, 635-638, 641-642.
Puchstein and Lloyd, Alternating-Current Machines, 1948, pp. 316-317.
Uwe Hansen, Germany Patent 3402035, Jul. 25, 1985, English abstract.
McAllister, Alternating Current Motors, 1909, pp. 74-79.
Holec Projects B.V.
Hoover Robert Lloyd
Pellinen A. D.
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