Proposals for a practical calibration method for mechanical torque measurement on the wind turbine drive train under test on a test bench

Hongkun Zhang,Jan Wenske,Mohsen Neshati,Andreas Reuter

doi:10.1002/we.2472

Hongkun Zhang, Jan Wenske + Show 2 more

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https://doi.org/10.1002/we.2472

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Abstract

AbstractThe mechanical torque input into the wind turbine drive train is a very useful measurement for tests performed on a test bench. To ensure the accuracy and the reliability, an accurate calibration of the torque measurement must be carried out and repeated within a certain period of time. However, owing to the high torque level and large structure size, such a calibration is both expensive and time consuming. To overcome this challenge, a new calibration method is proposed here. The method is based on the electrical power measurement, where a high level of accuracy is much easier to achieve. With the help of a special test process, a relationship between the torque‐measuring signal and the electrical power can be established. The process comprises two tests with the drive train running in different operating modes. The calibration is possible by carrying out the same test process on several different torque levels. Detailed uncertainty analysis of the method is presented, whereby the uncertainty can be calculated by means of matrix operation and also numerically. As a demonstration, the implementation of the method on a test bench drive train that contains two 5‐MW motors in tandem with the motors operating in a back‐to‐back configuration is also presented. Finally, some variations on the method and possible ways of achieving better accuracy are discussed.

Highlights

The mechanical torque plays a very important role in the power transmission of wind turbines, transferring the mechanical power gained by the rotor all the way to the generator
The mechanical torque input into the wind turbine drive train is a very useful measurement for tests performed on a test bench
This paper proposes a new calibration method that establishes a relationship between the torque and the electrical power, so that the torque measurement is indirectly calibrated through the electrical measurement

Summary

Introduction

The mechanical torque plays a very important role in the power transmission of wind turbines, transferring the mechanical power gained by the rotor all the way to the generator. Torque measurement is vital for the determination of the drive train efficiency, as well as the aerodynamic efficiency of the rotor. Multi-MW wind turbines have one of the highest torque levels found in modern industries, along with hydro power and the shipbuilding, for example. A calibration traceable to a national or international standard at this level is not possible at present, since the largest such calibration capacity available anywhere in the world is only 1.1 MN·m,1 which is owned by the German national metrology institute PTB in Braunschweig. The governing calibration standard is the German DIN 51309 standard.[2] A new torque standard machine with a capacity of 5 MN·m is under development at the PTB.[3] Until adequate calibration capacity becomes available, the torque measurement can only be partially calibrated. The PTB has developed a 5-MN·m reference torque transducer

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