SAFETY DEVICE FOR WINDMILLS

Abstract: Device to protect the turbine and generator of a windmill against abnormal stresses as for example high wind velocities, loss of electric power in the network, excessive temperatures, and mechanical vibrations. The device is provided with indicators (22, 23, 24a, 24b) which register such abnormal operating conditions, and with a releasable coupling (15) which can be connected with both the turbine shaft (20 and 28 respectively) and with a cog wheel (7) fitted to the turbine mast. In the event of abnormal stress, the motion of the turbine is transmitted to cause a turning movement in the plant, with the turbine turning so that its plane of rotation becomes parallel to the direction of the wind.

Description: SAFETY DEVICE FOR WINDMILLS The invention herein presented concerns a device in a windmill comprising a . horizontally housed turbine with a generator also attached to the shaft of the turbine, so that the turbine and generator are located at the top of a mast and can be turned so as to protect the turbine and generator against abnormal stresses, as for example loss of electric power in the network, high wind velocities, excessive temperature, and mechanical vibrations in the plant. As is well known, a wind turbine which can operate a generator may be used to produce electrical energy. The turbine is customarily situated at the top of a mast and may be turned. With the turbine located at a certain distance from the center of the mast, the turbine will turn by itself in the wind and assume a - . During operation the plant may be exposed to impermissible stresses which can cause damage. At very high wind velocities, for example, the turbine is 5 subjected to great mechanical stresses, and the generator will produce outputs in excess of those specified as permissible. Moreover, there may be a loss of electrical power in the network connected to the generator. The turbine will then increase its speed of rotation to an u excessive level . To protect the turbine and generator against such impermissible stresses, various devices have been employed in-plants up to the present time. For example mechanical brakes or air brakes have been used on the 5 turbine blades. Further, a foldable or rotatable fin has been fitted to the plant, turning the plant out of .the . wind. However, the existing devices have not proven .effective enough to provide adequate protection for "the turbine and generator under abnormal operating conditions. β - • The purpose of the invention herein .presented is to achive an arrangement which makes it possible to protect the turbine and generator effectively from impermissible stresses. The device does so by virtue of the following principal features; indicators designed to register 5 abnormal operating conditions, and a releasable coupling so designed that under abnormal operating condtions it is coupled directly or indirectly by electromagnetic effect to the turbine shaft and also to a shaft provided with a gear wheel which meshes with a cog wheel fitted -0; .to the mast, thus transmitting the motion of the turbine turning so that its plane of rotation becomes nearly parallel with the direction of the wind. The invention will be described more in detail with reference to the attached diagrams, where Figures 1a and 5= 1b present an overall view of the wind turbine as seen from the side and front, respectively, igure 2 shows a plant, partly in cross section, with a synchronous generator. Figure 3 shows a plant, partly in cross secJjLfij-b "" Figures 1a and 1b shows a windmill designed in accordan with the invention. The mast 1 is fixed in place by means of attachments 2 on base 3. The mast 1 is also provided with stays 4 and 5 for raising and lowering .it. At the top of the ma x st, the gondola is disposed to permit turning, so that the turbine can assume a suitable position in relation to the direction of the wind. A generator 8 is attached at the gondola. The turbine, with the turbine hub 10 and rotor blades 9, is set on the . same shaft as the generator. Centrifugal weights 11 are attached to the blades. On the base of the mast, there is a box-like room or similar structure where- all the electrical control facilities are located. - Figure 2 shows the plant, but in detail, with the generator consisting of a synchronous generator 8. The generator and the turbine hub 10 are set on a: common fixed hollow shaft. Whithin the fixed hollow shVft, there is a drive shaft 20 connected to the turbine; the drive shaft is connected by a universal joint 19 to the shaft 18 leading to the releasable coupling 15, which can be joined to the shaft leading out 21. This shaft is connected by means of a bevel- gear drive 13 to the vertical shaft 12 which is provide with a gear wheel 14. This gear wheel meshes in turn with a cog wheel 7 which is fitted around the mast 1. The releasable coupling 15 is normally held in the disengaged position by means of the electromagnet 16. Thus, when the magnet 16 is subjected to electric current from a power source, the coupling is disengaged. When the current is interrupted, the pull of the magnet 16 ceases, and the spring 17 returns the releasable coupling to the engaged -position. This means that the shaft 20, via the universal joint 19, the shaft 18, the releasable coupling 15, the shaft 21, bevelgear drive13, the shaft 12 and the gear wheel 14, is connecte with the fixed cog wheel 7 on the mast, The rotation of the turbine will then be.transmitted to the gear wheel 14, so that the gondola turns itself out of the wind and the rotation plane of the turbine becomes nearly parallel with the direction of the w.ind. " In this position, the turbine will cease to rotate, and the plant will remain in this position. By means of this arrangement, the turbine can thus be disconnected if it is subjected to impermissible stresses of the. kind mentioned in the introduction. The indicators 22, 23 and 24 are connected to the plant. By means of these indicators, such as stresses in excess of the specified limits can be indicated. If, for example, there should be a loss of the • electricity in the network, the generator would have no load, or be overloaded. To protect the generator against this, one of the indicators 24a is designed to register the tension in the network and as necessary disconnect the pull magnet 16, so that the turbine is turned ou.t of the wind and stops. This indicator is located in the control room 12. Another indicator 24b is designed to register the output of the generator. This output becomes excessive if ' wind velocity is too high, and there is a danger that the windings of the generator will be burned. When the output registered reaches a certain level, the current to the pull magnet 16 is therefore interrupted, so that the turbine is disconnected. This indicator is also located in the control room 12. A third indicator 23 may b-e installed to register the temperature in the generator or its housing, so .that when a certain maximum permissible temperature is reached, the pull .magnet is released and the turbine disconnected. The indicator 23 is located close to the windings of the generator. Further, an indicator 22 is designed to register vibrations in the plant. For example, when ice forms on the rotorblades, an imbalance can arise in the turbine. A large imbalance can cause severe vibrations which can damagethe plant. This indicator is located at the top of the mast underneath the yaw bearing and releases the pull magnet in the event of severe vibration. The plant is then disconnected, and the lockable coupling thus turns the turbine to a : position where its plane of rotation is in parallel .with the direction of the wind. Since the abnormal operation conditions can change - for example, the wind can die down - the turbine is turned out of the wind only for a limited interval of time. To achive this, a timed relay, for example, may be used and ' set at an appropriate time interval. By means of the relay, the electric current to the pull magnet is interrupted for the desired length of time, after which the. current is restored. The turbine then turns toward the wind and resumes supplying power. If some abnormal operating condition again is registere the puli magnet is again released, and the turbine turns out of the wind and is disconnected. Here both the registration of abnormal operating conditions, and the resumption of normal operation are done automatically. Thepull magnet 16 of the coupling 15 is operated from the control panel 12, which as mentioned may be placed at the base of the mast. From this control panel it is also possible to control the pull magnet manually, so that the plant can be disconnected for inspection and service, for example. As indicated, Figure 2 shows the turbine connected to a synchronous generator 8. This consists of a 1 ow-rotational -speed generator of the reluctance type designed to supply current to an electric power network. Figure 3 shows another design, in which the generator is asynchronous. The generator has a high rotational speed and is equipped with a gear reduction set 25. In this design, the motion of the turbine is transmitte from the shaft leading in 28 to the bevelgear drive 13 by means of a gearbelt drive transmission 27. With the pull magnet 16 the rotation of the turbine is connected to the gear wheel 14 in the same plant are indicated. The- device described provides automatic d sconnection of the plant under abnormal operating conditions and thereby protects the plant against damage. The device is not restricted to the form of design described above; variations in different respects are of cource possible within the scope of the invention. -~y-

Claims: Pa ten t cl a i ms 1. Device in windmills comprising a horizontallay housed turbine, with a generator also attached o the shaft of the turbine, so that the turbine and generator located at the top of a mast can be turned so as to protect the turbine and generator against abnormal stresses, • as for exmple loss of electric power in the network, high wind velocities, excessive temperature, and mechanical vibrations in the plant, featuring the indicators (22, 23 24a and b) designed to register abnormal operating conditions and also featuring a relesable coupling (15) designed, when abnormal operating " conditions are registered, by electro¬ magnetic influence to connect, either directly or indirectly, the rotation of the turbine shaft to a shaft provided with a gear wheel (14) which meshes with a . cog wheel (7) fitted to the mast, thus trans- mitting the motion of the turbine to cause a turning πvQ-vement in the plant, with the turbine turning so that its plane of rotation becomes parallel with the direction of the wind. Device in accordance with patent claim 1 for influencin the detachable coupling (15), featuring a full magnet (16) influenced by electric current for disengagement and a spring device (17) for restoring to the engaged position. Device in accordance with patent claim 2, featuring a timed relay designed to be switched on when the pull magnet (16) is released, and designed to be switched on for the time that the plant is desired to be disconnected. Device in accordance with patent claim 1 , featuring an indicator comprising a device to register the voltage in the electric power network. Device in accordance with patent claim 1 , featuring an indicator comprising a device to • reg ister g e ~ --f m^s-~ 6. Device in accordance with patent claim 1, featuring an indicator comprising a device to register temperature. Decive in accordance with patent claim .1, featuring an indicator comprising a device to register vibration, 8. Device in accordance with patent claims 1-7 for abnormal operating conditions not capable of indication by the above mentioned indicator devices, featuring a device for manual control of the detachable coupling.

Inventors: WERNER PER-AXEL, WERNER, PER-AXEL
Applicants: SVENSK VINDKRAFT IND AB SVIAB, SVENSK VINDKRAFT INDUSTRI AB (SVIAB)
Application year: 1981
Main classification: F03D7
IPC codes: F03D7