Abstract:
One aspect of the present invention concerns a generator for a hydroelectric power station, having a stator and a rotatably mounted rotor, and first vanes which act on the rotor and which cause rotation of the rotor. In order for the generator to be of a smaller structural size the stator is mounted rotatably and there are provided second vanes which act on the stator and which cause rotation of the stator in a direction opposite to the rotation of the rotor.

Description:
RELATED INFORMATION 
     The present invention concerns a generator having a stator and a rotatably mounted rotor, and first vanes which act on the rotor and which cause rotation of the rotor, and a hydroelectric power station having such a generator. 
     A generator for a hydroelectric power station is known from the state of the art, for example from CH 31 69 00, FR 1 082 831, DE-A1 199 07 180 and U.S. Pat. No. 4,289,971. 
     That kind of generators is generally known and is used for example in falling water power stations on reservoirs. It will be appreciated that, in all generators, there is an interaction between structural size and rotary speed. The higher the rotary speed of the rotor (for example a Pelton turbine), the correspondingly smaller can the generator be, with the same output—or expressed the other way round: the slower the rotor rotates (for example a Francis turbine), the correspondingly greater is the structure of the generator. 
     It will be appreciated that there is the possibility of providing a transmission between the first vanes which cause rotation of the rotor and the rotor of the generator, the transmission producing a high rotary speed for the rotor. As a result the generator itself could turn out to be relatively small. It will be noted however that the transmission reduces the level of efficiency of the installation, forms a potential source of trouble and naturally must be driven at a sufficiently high torque which in turn requires correspondingly large items of equipment such as rotor blades or guide vanes. 
     The object of one aspect of the present invention is to provide a generator which avoids the disadvantages involved in the use of a transmission but which nonetheless is of a small structure. 
     In accordance with one aspect of the invention, in a generator of the kind set forth in the opening part of this specification, that object is attained in that the stator is mounted rotatably and that there are provided second vanes which act on the stator and which cause rotation of the stator in a direction opposite to the rotation of the rotor. 
     In that respect one aspect of the present invention is based on the realization that the criterion for the structural size of the generator is the relative speed between the rotor and the stator of the generator. When the generator has a stationary stator, that relative speed arises solely out of the rotational speed of the rotor. If however the stator is mounted rotatably and rotates in a direction in opposite relationship to the direction of rotation of the rotation of the rotor, the two speeds are added together so that the sum of both speeds of rotation becomes effective. Accordingly the size of the generator can be halved, with the same output. 
     In order to embody a simple structure for the generator, a preferred embodiment of one aspect of the invention provides that the first and/or second vanes act by way of a shaft on the rotor and on the stator respectively. 
     So that operation in a fluid medium such as water is possible, the generator must be safely protected from moisture in a housing. In order to provide for a simple design configuration for the housing, it is of a multi-part nature and the stator is mounted in a water-tightly sealed part of the housing, which in turn is mounted rotatably and on the outside of which the second vanes are arranged. In that way the second vanes can produce rotation of the housing with the stator installed therein. 
     A rotor shaft can in turn be mounted rotatably in that housing, the rotor shaft on the one hand carrying the rotor and on the other hand, at a portion disposed outside the housing, carrying a further housing portion on which the first vanes are mounted in order to cause rotation of the shaft and thus the rotor of the generator. 
     In a particularly preferred development of one aspect of the invention the spacing of the vanes relative to each other is such that the aqua fauna is put at risk to the minimum possible extent. That involves on the one hand the respective spacing of the first and second vanes from each other in the peripheral direction and on the other hand the spacing between the first and second vanes in order to ensure that for example fish are not simultaneously exposed to the first and second vanes. 
    
    
     
       BREIF DESCRIPTION OF DRAWINGS 
       Aspects of the invention are described in greater detail hereinafter with reference to the accompanying Figures in which: 
         FIG. 1  is a simplified cross-sectional view of a generator according to one embodiment of aspects of the invention, and 
         FIG. 2  shows the pressure pattern in the water when flowing through the generator. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a generator arranged in a flow passage  10 . In this case the direction of flow of the water is from left to right in the Figure. The generator is supported by supports  40  which in the Figure are a component part of the flow passage  10 . It will be appreciated that those supports  40  can equally be subsequently fitted in an existing flow passage  10 , together with the generator. 
     In this case, the flow passage  10  is of a tubular configuration and at its ends has flanges  15 , with which a connection can be made to passage portions (not shown) which are already present. That design configuration permits mounting or repair of the generator in the flow passage  10  when released from the other passage portions. As carrier eyes  11  are provided on the flow passage  10 , replacement or release of the flow passage  10  from the other passage portions can be correspondingly easily implemented. 
     The generator illustrated in the flow passage  10  has essentially two housing portions, a front portion  14  and a rear portion  12 . In this case the front housing portion  14  is of a streamlined configuration and avoids a dynamic build-up of the flowing water upstream of the generator. 
     The rear housing portion  12  accommodates the generator with the rotor and the stator  22  and further contains an exciter machine  28  for transmitting the exciter power to the rotor  22  of the generator. 
     As a relative movement is required between the rotor  20  and the stator  22 , the rotor  20  is held and mounted rotatably with a rotor shaft  18  in the rear housing portion  12 . In this case by way of example that mounting effect is afforded by way of rotary connections  30  and  31  as front and rear rotor mountings. In order to seal off the rear housing portion  12  in relation to the water, the arrangement has a seal  38  which is shown in simplified form in the Figure as an individual sealing lip but which can also be in the form of any other suitable seal. 
     The generator is arranged in the supports  40  with a front water-lubricated bearing  34  and a rear water-lubricated bearing  36 . Those water-cooled bearings  34 ,  36  are reliably lubricated by a permanent supply of the lubricant—namely water—during operation. In addition, the water flowing through the arrangement is not endangered by other lubricants such as greases or the like. 
     That mounting arrangement permits rotation of the rotor  20  and the stator  22  of the generator in opposite directions. In order to supply the exciter power and to carry away the electrical power generated, the shaft  19  which is mounted in the rear, water-lubricated bearing  36  must be in the form of a hollow shaft in order to permit cables to be passed therethrough from a slip ring member  26  into the interior of the rear housing portion  12 . The cable run is not shown in order to avoid unnecessarily restricting clarity of the Figure. 
     The mode of operation of this generator is described hereinafter. The water flowing through the flow passage  10  firstly impinges on the first vanes  16 . Those first vanes  16  are connected to the rotor shaft  18  by way of a hub  17  at such an angle of incidence that it is caused to rotate, for example in the clockwise direction. In that respect the hub  17  and the vanes  16  are of such dimensions that they receive approximately half the kinetic energy of the water and convert it into rotary movement. 
     After the water has flowed further on in the flow passage  10 , it reaches the rear housing portion  12  with the second vanes  24 . In that case the angle of incidence of those vanes  24  is so selected and the vanes  24  are so dimensioned that the afflux flow of water also causes rotational movement of the rear housing portion  12  with the stator  22  of the generator, which is fixed therein. In the present example, it will be assumed that the direction of rotation is counter-clockwise. In that situation the vanes  24  again take approximately half the kinetic energy from the water and convert it into rotational energy. 
     As the rear housing portion  12  with the stator rotates with respect to the flow passage  10  and the front housing portion  14  with the rotor  20  in turn rotates with respect to the rear housing portion  12 , the exciter power is fed by way of the slip ring member  26  through the shaft  19  in the form of a hollow shaft and an exciter machine  28  to the rotor  20  of the generator and the electrical power induced in the stator  22  of the generator is in turn taken away from the generator through the hollow shaft  19  and the slip ring member  26 . 
       FIG. 2  shows the pressure pattern in the water in the flow passage  10 . As the first vanes  16  and the second vanes  24  are so designed that they each take approximately half the kinetic energy from the water and as the first vanes  16  and the second vanes  24  rotate at a relatively low speed, the effects of the generator according to the invention on fish in the flow passage  10  are not as serious as the effects of comparable, conventional generators. 
     That is due in particular to the fact that conventional generators involve only one set of blades which in the best case take all the kinetic energy from the water and convert it into rotational energy. Accordingly, the maximum possible pressure drop occurs when flowing through that stage. In the case of the generator according to the invention, the pressure drop is distributed to two stages each involving approximately half the amount and accordingly less serious effects on the aqua fauna. 
     By virtue of the configuration and arrangement of the blades, it is possible to eliminate the installation of guide blades which are required in conventional generators in order to cause rotational movement of the water flowing into the generator or to cancel out again the rotational movement caused by a conventional generator. That function is performed here by the oppositely rotating first vanes  16  and second vanes  24 . Therefore, the inflowing water is displaced in a clockwise rotational movement by the first vanes  16  corresponding to the direction of rotation of the first vanes  16 . As however the second vanes  24  perform a counter-clockwise rotational movement, that clockwise rotational movement is thereby compensated again so that the discharge flow of water issues from the flow passage  10  in a substantially pressure-less condition and in a straight line.