Air gap generator monitoring
With very large generators and electric motors, it’s important to determine the radial run out of the rotor inside the motor compared to the stator. Due to imbalances during operation, which could be due to wear caused by extreme wind and weather conditions, the rotor might touch the stator, which could lead to catastrophic failure. Therefore, non-contact optical and capacitive sensors are used to measure the distance between the stator and rotor and to monitor the rotor gap whilst the motor is running. Non-contact capacitive sensors provide long-term stability, reliability and temperature stability.
During air gap monitoring in a wind turbine generator, the average temperature is 120°C. Some suppliers such as Micro-Epsilon offer capacitive sensors that are specially adapted to measurements in a generator. They are resistant to vibration and are protected by a special housing. Their unique triaxial design enables flush installation into electrically conductive materials as the guard ring electrode and grounding are also located on the front edge of the sensor alongside the measurement electrode.
The gearbox temperature is measured during operation. Heating up of gearbox components may indicate a potential problem with a component. Subsequent remedial action can be started or maintenance planned.
In order to control air supply, the air flaps automatically open and close depending on the temperature. Draw-wire displacement sensors are able to monitor the position of the open air flap.
Supporting moments of the nacelle
In order to monitor the supporting moments, eddy current displacement sensors measure the distance between the wind turbine nacelle and the tower, which enables early recognition of any fluctuations.
Non-contact laser triangulation sensors are ideal for measuring the distance between the tower and the foundation. High measuring rates enable the sensors to detect any changes reliably. Depending on the number of sensors installed, detailed evaluations about the vibration behaviour of the mast can be determined.
Test rigs for measuring rotor stress
Test rigs have been developed for load tests on wind turbine rotor blades, which simulate the real loads caused by high winds and extreme weather conditions. The tip of the rotor blade can be distorted by up to 10 metres due to mechanical loads. Draw-wire sensors are mounted on these test rigs for measuring this distortion. Two sensors per traction point measure the deflection and torsion of the rotor blade. The draw-wire sensors operate with measuring ranges between 3m and 10m. The digital signal output is provided for further simulation and analyses.