| Summary: | A novel concept for a wave power plant is being developed at the Division for Electricity and Lightning Research at Uppsala University. The concept is based on a permanent magnet linear generator placed on the seabed, directly driven by a surface following buoy. Critical for the survival of the generator is that the air gap between the moving and static parts of the generator is constantly fixed at the designed width to prevent the moving and static parts from connecting during operation. The aim of this thesis was the development and evaluation of a sensor for measuring the air gap during the operation of the generator. Additionally, in order to survive during years on the sea floor inside the wave power plants, the sensor was required to be a passive component, as well as robust and compact. A coil etched on a printed circuit board, i.e. a search coil, was the chosen basis for the sensor. The sensor was tested on an existing test rig of a wave power plant and the results were compared with theoretical calculations. The results show that a search coil magnetic sensor etched on a printed circuit board is a good concept for measuring the air gap. Experimentally measured and theoretically calculated sensor signals showed very good agreement. The designed sensor has a sensitivity of +/- 0.4 mm in the range of 4 – 9.5 mm air gap. The potential for future improvements of the sensor’s sensitivity is large.
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