Novel torque sensors aid tidal turbine development10 August 2010

Novel non-contact torque sensors are playing an interesting part in the development of commercial-scale in tidal turbines, being built by Irish marine technology firm, OpenHydro.

The company is using Sensor Technology devices, based on surface acoustic wave (SAW) technology, to measure rotational speed and frictional forces for the turbine bearings in its simulator, to optimise the design.

Because OpenHydro's turbines are intended for deep submersion, they use open-centre turbine designs that can be deployed directly on the seabed.

However, OpenHydro mechanical engineer Kevin Harnett explains that, installation in such inaccessible locations makes reliability a prime consideration.

Hence the evaluation work, which, for the bearings, means determining how frictional forces vary with loads and rotational speeds – and hence also the measurement of torque in a shaft from the motor that drives the bearing under test.

That's hard to do with conventional sensors, but Harnett says that Sensor Technology's TorqSense RWT320 is providing an ideal solution. "We chose the RWT320 because of its convenient wireless operation, and because it was easy for us to fix in line with an existing shaft in our experimental set up," reports Harnett.

"In addition, this model of sensor has integral electronics and a serial output, which means that we can link it directly to a laptop in our test laboratory. This is a very straightforward and convenient arrangement," he adds.

OpenHydro is also using Sensor Technology's TorqView software, which provides dial, digital bar and chart graph displays for torque, rpm, temperature and power – as well as facilities for real-time plotting and data recording.

"We have found both the sensor and the software very easy to work with," comments Harnett, "and the sensor has proved itself to be well able to withstand the tough operating conditions in our laboratory. Overall, we're very happy with product and the service we've received. The sensor is providing invaluable data for our development work."

Brian Tinham

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