DYNAMIC FEATURES OF SPEED INCREASERS FROM MECHATRONIC WIND SYSTEM

The paper main objectives are to extend the library of planetary increasers that can be used in wind systems and to establish the dynamic properties of a speed increaser that are necessary in the controller design. The proposed increasers are derived from some representative speed reducers by flow power inversion.

The wind turbines are designed for certain environmental parameters (wind power). Most wind turbines trainsinclude a gearbox to increase the speed of the input shaft to the generator. An increase in speed is needed because the wind turbines rotors shafts turn at a much lower speed than is required by most electrical generators. A sensor of the control system measures any changes in the wind power, and a control plate commands the speed increaser coupling/decoupling from the system, in order to function at the efficient level. Taking into account these considerations, it can be derived that it is important for the wind system running, to establish the premises necessary in designing the control system, part of these requirements being given by the speed increaser dynamics. Therefore, the paper main objectives are the enlargement of the library of speed increasers for wind systems, and the establishment of the increaser dynamic model. The first objective is achieved in the first part of the paper, by proposing new solutions of speed increasers with high transmission ratios and efficiencies, which are derived from some representative speed reducers by wind power inversion. A comparative analysis of the structural and dynamic specific features of the different types of planetary speed increasers is also presented in the first part of the paper.

Fig. 1. Wind turbine

NEW

SOLUTIONS OF PLANETARY SPEED INCREASERSIn order to extend the library of planetary increasers that can be used in wind turbines, the first

step is to establish a list of requirements, taking into account the turbine and the generator prerequisites. Thus, a speed increaser for wind must accomplish the following main requirements:

1) the increase of the multiplication ratio 2) an acceptable efficiency , 3) the reduction of the radial / axial overall size, 4) the reduction of the complexity degree, 5) the reduction of the technological costs etc.The development of new schemes of speed increasers means the minimization of some of the

disadvantages, in the condition of an increased multiplication ratio. The schemes proposed in this paper take into account the cost reduction, by reducing the transmission complexity degree, while an acceptable efficiency and the necessary multiplication ratio are obtained.

A source in the development of new schemes of increasers with higher performances, which can be used in wind turbines is represented by the planetary reducers with a large technical use. The reducers with one sun gear, which were taken into account to generate speed increasers, are relatively new developments of the planetary reducers with two sun gears. These developments have, as main objective, the increase of the efficiency; the development is reduced to the replacement of one of the 2 gear pairs with a synchronic coupling with a superior efficiency. The increaser contains 2 satellites in parallel connection and a Schmidt semi-coupling with rollers or pins, which allows the satellites parallel and equiangular assembling.

Fig.2 Cycloidal Gear amplifier (Schmidt clutch type) with bolts and two satellites in parallel (overview)

CONCLUSIONSA) The reducers with one sun gear, used in the paper to generate speed increasers, are relatively recent developments of the planetary reducers with two sun gears. The solution consists in keeping only one of the two gear pairs and replacing the rest of the gear pairs by a synchronic coupling with a superior efficiency. The multiplication ratios of the speed increasers, the efficiencies and their expressions for speeds and torques B) A way to improve the transmission efficiency is referring to the use of internal cycloidal gears with rollers or pins, whose efficiencies are higher than of the involute gears. The speed increasers with cycloidal gears can obtain multiplication ratios that are comparable to the reduction ratios of the reducers from which they were derived; this type of increasers can obtain high multiplication ratios because the cycloidal gears can simply accomplish the condition z 1 (the difference between the numbers of teeth can be equal to 1, without the risk of interference). The results analysis highlight the fact that the planetary cycloidal reducers with one sun gear can be efficiently used as speed increasers by reversing the role of the input and output shafts; thus, a considerable enlargement of the library of speed increasers can be obtained.