Drive system for optimal energy production Drive systems with planetary drive motors and converters are always present from small systems for village power supply in India to the newest 5 MW leviathans. They provide an as high as possible energy yield and low risk potential for the system at the same time. With their help, the gondola and thus the wind turbine is constantly matched to the wind direction on the one hand, and on the other hand the rotor blades are brought into the ideal position. The systems are different depending on the size and configuration of the machine. The wind energy system manufacturer prefers a modular system which he can make use of in a flexible manner.Operation at the optimal speed is decisive for the efficiency of the energy producing drive train from the rotor to the generator. If it turns too slowly, insufficient energy will be produced; if it turns too quickly, there are dangers to the complete wind turbine. Two main final control elements ensure that the speed is kept as optimal as possible: One is for the positioning of the gondola which has to keep the rotor directly in the wind. The wind must always hit the rotor at right angles in order to ensure optimal exploitation of the power. The second final control element, which is responsible for the optimal speed, relates to the position of the individual rotor blades. The aerodynamics are influenced by the incline of the blades against the wind. In strong winds, the adjustment is made up to the break of the air stream with the consequence of rotor standstill.Always head-on to the wind
Given the huge dimensions and masses of the 5 MW turbines to be moved, which currently account for the performance peaks of the wind turbine construction, it is obvious which forces are necessary in order to perform the tasks described above. However, it is not only the movement torque but also the holding torque which are decisive for the design of the azimuth drive. Several geared motors with brakes are used in order to always put the gondola with its weight of more than 100 (metric) tons and a rotor span of up to two football pitches at right angles to the wind and keep it there. The sensor technology reports wind direction changes to a control unit which then puts several geared motors in motion in a matched way via the frequency converters in order to track the gondola. The tracking is usually triggered by a wind direction deviation of seven degrees. The requirements for precision and exactly matched drive behaviour are decisive for the choice of the drive system.A few thousand newtonmeters are sufficient for this task for small systems. The constructor will find suitable geared motors from 1,000 Nm rated torque in the Bonfiglioli product range. The azimuth drives were designed for 1.1 million Nm peak torque for the Repower 5 MW system recently put into operation. Eight single drives with specially designed planetary gear motors with 5.5 kW motors from the Bonfiglioli 700 series are used. They each yield 70,000 Nm rated torque and 140,000 Nm peak torque for a gear reduction of i = 1.281. They contribute to the high total weight of the gondola with their individual weights of 1.200 kg, a total of practically 10 (metric) tons; however they are the first choice with respect to their power-to-weight ratio. Rotor blades optimally positioned
The pitch drives, which are responsible for the efficiency of the complete system, behave similarly. They provide the maintenance of the optimal rotation speed via the position of the individual rotor blades. If the speeds are too high, there is a risk of the system being damaged by the wind pressure. In both cases, the adjustment of the rotor blade inclination is effective favourably. Here also, the thickness and at the same time the precision of the drives are sought after because the adjustment ranges are surprisingly small. The gear reduction ratios are in the range of 1:600 to 1:2000. The pitch controller reacts to the smallest changes in speed in the threshold range and effects a coordinated adjustment of the rotor blades via the three pitch drives in order not to exceed the maximum rotation speed.As well as the requirements already mentioned, due to the position in the rotor hub, the pitch drive must also be particularly small, light and easily installed for combination from case to case with angular gears as preliminary stage. In addition, these drives are fitted with special seals in order to perform their service in rotary positioning and also at the tip of the rotor in any weather conditions uncomplainingly year in year out Drive electronics have prerequisites
With decades of experience with geared motors in wind energy system construction behind it, Bonfiglioli now also provides the control and linking of the azimuth and pitch drives with its own frequency converters from the Bonfiglioli Vectron product range. The high end Active converter series meets all the conditions for this. Namely, it has a very economic internally developed system bus which also minimises the complexity for assembly and cabling. The compensation runs completely synchronously via the bus connection and thus always places and holds the system in the ideal position. Furthermore, the equipment itself also provides high flexibility for assembly and cooling and also solutions with the high IP 65 protection class. Thus, in conjunction with the planetary gear motor range, the system constructor is offered a construction kit of integrated and above all competitive solutions for both the important requirements for wind energy systems. Bonfiglioli also supplies the generator gearboxes for smaller systems. Here, the largest industrial gearbox manufacturer in Europe with 1.4 million units per year applies its experience in the construction of high torque planetary gears. Planetary gears up to 500,000 Nm are supplied in the standard series business. The requirements for compactness and low weight are best met with planetary gears. Low costs are guaranteed by the highly efficient production, which in the meantime has also achieved high quantities with the Mobilhydraulik (planetary gears with hydraulic motors) application.For other capacities, the experience of the Bonfiglioli Vectron subsidiary in Krefeld comes into play not only with the most up to date converter technology but also on the subject of mains regenerative feedback. The Bonfiglioli application engineers can resort to a wealth of experience of supplying energy into grids from applications outside drive technology, especially from photovoltaics. Thus there are no barriers to fitting out smaller and medium-sized plants with a complete system from Bonfiglioli. Worldwide experience
“The international wind energy systems market is very important for us” says Thomas Becker, CEO of Bonfiglioli Deutschland GmbH. “Germany is also leading in this field and we see additional growth opportunities despite our high market share”. Since starting its commitment to the wind energy systems market a quarter of a century ago, Bonfiglioli has experienced practically all the peaks and troughs of the sector. Becker: “Our advantages are our technical flexibility and our international presence. There are great differences in the requirements which we know in detail and can implement in close collaboration with our customers”. Hardly anyone in this market provides the power of the gearboxes and the precision of the control by the converters from the same source. Short response times, uncomplicated procedure and last but not least the common language help to rapidly resolve the detail problems of wind energy system manufacturers. Based on its long experience, the North Italian drive specialist builds a specific gearbox as required for every type of system and application and optimises the converters for each application case. Surprises must not occur either in the mechanics or in the electronics for the required 20 years service life. The planetary gear motors in the Bonfiglioli Trasmital product line have already proved this, because Bonfiglioli has a market share here of around 20% as one of the largest suppliers for azimuth drives and pitch drives. As regards the converters, Becker expects further upswing: “The appropriate drive system provides benefits for everyone, both the system constructor as well as the operator. In the end, the system is always optimally adjusted to the wind”.