Bench Talk

Wind turbines are a 21^st-century windmill that turn a breeze into electrical energy. From an engineering standpoint, these turbines are quite impressive masterpieces of design, with rotors reaching 80m in length that, combined, provide a swept area of 20,566m². In all, these leviathans often have more than 8,000 components, but perhaps surprisingly, some of the most critical components are just centimeters long: The many sensors that keep these engineering masterpieces functioning in the face of extraordinary stresses, vibration, and various other hazards.

More specifically, sensors are key because they provide data that helps prevent large-scale failures by:

• Detecting, monitoring, and communicating information about parameters such as changes in the distance between two components near each other
• Monitoring levels of vibration that, if excessive, can cause major damage
• Monitoring changes in temperature, pressure, and mechanical stresses

What types of sensors are used? A variety, including those that measure eddy current, displacement, and vibration, wind, and temperature:

Eddy Current Sensors

• Detect changes in the electrical current created when a conductive material enters a moving magnetic field. When this occurs, the strength of the field can be translated into changes in distance.
• Measure the lubricating gap of the shaft; changes in this gap can indicate the need for maintenance to prevent the shaft from binding or seizing.
• Measure how the turbine shaft rotates both axially and radially inside its housing, which is important in determining maintenance needs.
• Measure the turning effects (moments, or torque) applied to the nacelle caused by vibration, wind loads, or other factors that affect structural integrity.

Displacement Sensors

• Laser displacement sensors detect very small movements of the foundation in relation to the tower, which is needed to help indicate whether problems are developing and how rapidly it is progressing.
• Capacitive displacement sensors measure the generator air gap, which is needed to ensure conductive surfaces function in high-temperature environments and highly-electromagnetic fields.
• Draw-wire displacement sensors measure changes in distance in components that are located far away from the object that is moving.

Vibration, Wind, and Temperature Sensors

• Accelerometers detect and monitor vibration within main, yaw, and slew bearings, as well as other rotating components.
• Ultrasonic wind sensors measure the distance to an object by using sound waves, sending out a very-low-frequency sound wave and detecting the wave after it has been reflected by the target object.
• Wind sensors detect changes in temperature that are indicative of the overheating of some type of component or subsystem.

Sensors play a key role in reducing the likelihood of major failures in wind turbines. Eddy current and displacement sensors, accelerometers, and wind and temperatures sensors are key to monitoring turbines and communicating potential and needed maintenance.

For more information about wind turbines and the sensors that support them, check out Barry Manz’ article, “Wind Turbines: Tiny Sensors Play Big Role,” in Mouser’s Application and Technology site.