HBM measurement technology on the test stand: Dynamic torque measurement in water turbines
How can torque be measured more reliably and efficiently? A well-known manufacturer of test stands for water turbines trusts in a new concept: Instead of using a force transducer to measure torque indirectly through the restoring force, installing the T12 digital torque transducer gives significantly better results. Thus, smart measurement technology substantially increases efficiency in hydroelectric power generation.
Energy efficiency is one of the hottest topics today. Consequently, an accurate evaluation of the performance parameters of components used for power generation is very important. For example, the turbines required for hydroelectric power generation are subject to rigorous testing. Torque measurement plays a decisive role here.
Reliable data is best obtained performing test runs on the test stand. For this purpose, such test stands are generally equipped with a facility for indirect torque measurement comprising a vertically arranged, pivoted loading device (dynamometer).
Braking effect as constraint
This loading device is connected through a shaft train to the turbine installed underneath. If the turbine is driven by water flow (inverse operation), the loading device exerts a braking effect on the shaft train and is thus subject to rotational acceleration. As a result it would now rotate about its vertical axis, unless it did not rest on a force transducer by means of a lever arm. The supporting force (restoring force) is measured by a force transducer; the measured value multiplied by the length of the lever arm gives the reaction moment.
The system described above provides good results; however, it has two major constraints:
- The measured torque value is modified by the value of the friction moment in the bearing and
- No definitive statements can be made about the dynamics of the measured torque, because the loading device's mass moment of inertia exerts a strong damping effect.
Direct mounting of a torque flange
To eliminate these constraints, the water turbine test stand of a well-known company is to be modified so that instead of the force transducer a torque flange is directly mounted in the shaft train between the turbine and the (blocked) loading device.
This design no longer requires any lever arm, force transducer, and bearing of the loading device, however, they can continue to be used for alternative comparison measurements.
HBM's measurement solution: Digital torque measurement using T12
HBM offers the adequate solution for implementing this highly dynamic water turbine test stand. The T12 digital torque transducer plays a key role; it is directly mounted into the drive train between the turbine and the loading device.
There are many reasons for using T12 - the transducer sets standards in precision, dynamics, and signal resolution.
T12 is the first torque transducer ever to provide results with highest accuracy and resolution - pushing the physical limits of strain gage technology - over a measurement frequency range from 0 Hz to 6,000 Hz.
The special analog-to-digital conversion method enables the analog signal to be digitized without loss of information; 19-bit resolution allows measurement of large and small signal amplitudes without having to switch measuring ranges.
These and more special features make T12 ideal for integration into test stands for water power turbines and ensure secure and reliable test results. Hence, T12 contributes to further optimizing turbines with regard to energy efficiency.
