In the course of the research project, the T30FN torque transducer offering 10 kN•m nominal (rated) torque was used.
The F in the type name refers to the frequency-modulated signal transmission method. This means contactless measurement signal and energy supply of the rotor without any influence of the coupling factors, for example air gap variations.
The N in the type name designates integrated magnetic rotational speed measurement. The mechanical power as the generator input quantity can be determined from torque and rotational speed.
Fig. 2 shows the torque transducer installed on top of the mast.
Fig. 3 clearly shows the relationship between wind speed and torque [2]. Torque increases with increasing wind force - while rotational speed remains unchanged.
The result: Additional mechanical power is generated. However, this also means that the generator can produce more electrical power.
Today, the wind energy is one of the major renewable energies and continues to be a market of the future with attractive growth rates. Furthermore, energy requirements have rapidly increased and the demand for alternative forms of energy has virtually exploded as a result of nuclear phase-out.
At the beginning of the 1990s, a wind turbine's average rated output was 200 kW. Today, it amounts to 2 MW. There has been an increase in rated output by factor 10 over just under 15 years. This increase mainly results from larger rotor diameters. Doubling the rotor diameter gives a quadrupling of the effective area.
Rotating torque sensors are incredibly precise instruments used to ensure peak performance in a variety of mechanical systems, from automotive drivetrains to wind turbines. Engineers take the time to carefully select the right type of torque transducer (analog/digital telemetry, circular shaft, reaction torque, etc.), and the same level of consideration should be paid to installing the device into the test and measurement driveline.
The output of a rotating body is obtained from the product of torque and angular speed.
P = Output in N•m/s (1N•m/s = 1 W = 0.00136 metric hp)
M = Torque in N m
ω = Angular speed in s-1
N = Rotational speed in rpm
Transformation and some other steps give the relationship for torque, the quantity to be measured.
The calculated torque must by no means be directly used as the basis for selecting the torque flange, because it does not take into account any additional influencing factors, for example starting performance or vibration. General information about torque measurement is provided in [3].
Suitable sensor technology must be employed to detect the damage to wind turbine rotor blades early enough and minimize the economic consequences. Discover more about this Structural Health Monitoring (SHM) system testing and new measurement technology.
Torque to be measured often ranges from the kilonewton range (kN•m) up to several Mega-Newtons (MN•m).This is to be illustrated by the following example:
Generator: P=2 MW
Gear unit: 1:100
The generator power of 2 MW and a rotational speed of 1500 rpm give the following formula:
(1) MD=12.74 kN•m / n=1500 rpm
(2) MD=1.3 MN•m / n=15 rpm
Bigger generators with lower rotational speeds are being discussed. However, the torque transducers will then reach their limits as well. Fig. 5 shows the implementation of a 1.5 MN transducer and a design proposal for higher nominal (rated) torques.
Fig. 5: Implementation of a 1.5 MN transducer and design proposal
However, the traceability of a calibration of this huge torque transducer is not guaranteed. The German National Metrology Institute (PTB) in Brunswick, Germany, houses the world's largest torque calibration machine at present. It enables test equipment up to 1.1 MN torque to be calibrated with 0.1% measurement uncertainty [6]. HBM's (now HBK) current torque calibration offer is shown in Fig. 6.
Fig. 6: HBM's torque calibration offer (at the moment of this article)
[1] Herbert Lauer: Die Windkraft meßtechnisch erfaßt, Markt&Technik No. 44 dated October 30, 1981
[2] MESSTECHNISCHE BRIEFE, MTB 17 (1981) Issue 2, Published by Hottinger Baldwin Messtechnik GmbH, 64293 Darmstadt
[3] Rainer Schicker, Georg Wegener: Measuring Torque Correctly, ISBN 3-00-008945-4
Published by Hottinger Baldwin Messtechnik GmbH, Darmstadt
[4] energiewelten.de
[5] Christian Scheer, Rainer Schicker: Energie wird knapp. Getriebe und moderne Drehmomentmesstechnik tragen zur Energieerzeugung aus Windenergie bei, Windkraftkonstruktion
[6] https://www.ptb.de/cms/index.php?id=2447
Rainer Schicker, International Product Manager Torque Applications, HBM (now HBK) Test and Measurement
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
