Wind turbine terms

The cross-sectional shape of the blade. Wind turbines use thick sections from the NACA or DU families.

The steel stud cage cast into the foundation that the first tower section bolts down to.

A certified fixed point that safety equipment may be attached to.

The wind speed sensor on top of the nacelle. The controller decides cut-in and cut-out from it.

The angle between the relative wind and the blade chord. Too large and the flow separates: the blade stalls.

The automatic greaser that pumps measured grease into bearings and gear teeth on a schedule.

The share of time the turbine is available to produce. Contracts often penalise anything under 97 percent.

The theoretical maximum a rotor can extract: 59.3 percent, or 16/27. It cannot be beaten.

An aerodynamic shell of glass or carbon fibre composite. On an N90 it is 43.8 m long and weighs six to seven tonnes on its own.

The toothed slewing bearing between blade root and hub that lets the blade rotate.

The cylindrical end of the blade that bolts to the hub, held by hundreds of studs.

The outermost end of the blade. It sees the highest speed and the worst erosion.

Stretching the bolt directly with a hydraulic tensioner and seating the nut. Preferred on large flanges.

Inspecting inside the gearbox with a camera without opening it. The fastest way to see tooth surface damage.

The friction element in the brake caliper. Measuring pad wear is a standard item in every scheduled service.

Annual energy produced divided by what the machine would make running flat out all year. Typical onshore values in Türkiye are 30 to 38 percent.

The distance from leading edge to trailing edge of a blade section. It tapers from root to tip.

The switching device that interrupts fault current. Vacuum types are common at medium voltage.

The process of testing a newly built turbine and bringing it into production.

Vibration sensors permanently installed in the nacelle for continuous monitoring.

The slight forward opening of the blades out of the rotor plane, serving the same purpose.

A space with restricted entry and poor ventilation. The hub and the inside of a blade both count.

An electromagnetically operated power switch, used in motor control.

The power electronics that match generator output to grid voltage and frequency.

The radiator and fan set that cools gearbox oil and the generator. One of the biggest sources of summer alarms.

Repair after a failure. It is unplanned and the downtime cost is high.

The flexible connection between gearbox and generator. It absorbs misalignment and vibration, and slips under overload.

Deliberately reducing output because of the grid, noise or shadow limits. It is not a fault.

The lowest wind speed at which the turbine starts producing, typically 3 to 4 m/s.

The upper limit where the turbine shuts down for safety, usually 25 m/s.

Composite layers separating from each other. It heads the list of structural blade damage.

A generator whose rotor winding is fed through a converter. It makes variable speed economical; this is what the N90 uses.

A design where the rotor turns the generator without a gearbox. Enercon's signature.

The mechanical brake on the high-speed shaft. It backs up aerodynamic braking and holds the rotor for parking and service.

Time the turbine cannot produce. In contracts it has a price.

Bonding equipment to earth potential. The basis of both lightning and touch safety.

A stop triggered by a red button, breaking the safety chain directly. The blades go to feather.

A sensor measuring angle or speed. Pitch and yaw position are read from it.

The device that locks onto the ladder rail or rope and stops a fall.

The number the control system raises for a specific fault. Most service work follows that number.

Turning the blade roughly 90 degrees so it offers minimum resistance. It is the primary way to stop a turbine.

The ring-shaped face where two sections meet and are bolted together. The most critical place for torque checks.

The reinforced concrete mass that carries the turbine. A machine in the N90 class sits on 500 to 800 m³ of concrete.

A drive that sets motor speed by changing frequency, used on yaw and pitch motors.

Wear and corrosion at tightly fitted surfaces caused by micro-movement.

The wearer's side of the fall arrest system. It is inspected by eye before every use.

A converter the whole generator output passes through. It gives the most flexible grid compliance.

The transmission that steps the rotor's roughly 15 rpm up to the 1,500 rpm the generator needs.

The machine that turns mechanical rotation into electricity. The N90 uses a doubly-fed induction type.

The body that sets the industry's common training standard. Its certificates are effectively mandatory for site access.

The thickened oil used in bearings and gear teeth. The wrong type will finish a bearing.

The rules a plant must follow to connect to and behave on the grid. They differ by country.

Distorting current and voltage components at multiples of the fundamental frequency, produced by power electronics.

The parallel-shaft stages after the planetary stage. These do most of the speed increase.

The shaft between gearbox output and generator. The mechanical disc brake usually sits on it.

The screen through which an operator talks to the turbine, on the panel at the tower base.

The cast structure the blades bolt onto, carried by the main shaft. It houses the pitch drives and their backup batteries.

The pump and accumulator set that supplies pressure to brakes, pitch or locking systems.

Ice forming on the blade. It causes imbalance, lost output and an ice-throw risk, and calls for a shutdown.

A generator whose rotor turns with slip relative to grid frequency. Simple and rugged.

The rounded edge that meets the wind first. Rain and dust erosion starts here.

Wear of the blade's leading edge from rain and dust. It costs production and is repaired with coating.

The chain of receptor, conductor and earthing. One of the most frequently measured systems on site.

The metal disc at the blade tip. It catches the strike and takes it down a conductor to earth.

A switch detecting a mechanical end position. It stops pitch and yaw from over-travelling.

Cutting the energy and securing it with a physical lock and tag. The first step of any electrical work.

The turbine's ability to stay connected through a short grid voltage dip. It is a grid code requirement.

The shaft between hub and gearbox, turning at rotor speed.

The large bearing supporting the main shaft. Replacing it is one of the most expensive failures in the machine.

The shaft that carries the slow rotation from the hub into the gearbox.

Replacing a heavy part such as a gearbox, generator or blade using a crane. A costly operation lasting days.

Generally the 6 to 36 kV range. The turbine transformer output and site distribution sit here.

An independent measurement mast on site. It is the reference for power curve verification.

The machine house on top of the tower. It holds the main bearing, gearbox, brake, generator and control cabinet.

Testing a gear oil sample for metal particles and chemical degradation. It warns early.

A generator with magnets in the rotor, needing no excitation current. Common on direct drive machines.

The system that makes sure risky work is done under a written permit and defined conditions.

Setting power and loads by rotating the blade about its axis. The standard on modern machines.

The electric (or hydraulic) drive that turns the blade. On loss of supply, batteries drive it to feather.

The system that rotates each blade about its own axis to set the angle of attack and therefore the power.

Small pits forming on a bearing or tooth surface. The early stage of fatigue damage.

The high-torque input stage of the gearbox, which spreads load across several planet gears.

The turbine's main control computer. It reads every sensor, drives every actuator and raises the alarms.

How much of the wind's energy the rotor actually takes. A good machine peaks around 0.45 to 0.50.

The curve of power against wind speed. It is the turbine's identity card.

The ratio of active to apparent power. The grid operator usually dictates a band for it.

Helmet, glasses, gloves, steel-toed boots, hearing protection and harness.

The slight upwind curvature built into the blade. It keeps the tip clear of the tower under load.

Catching a failure early from vibration, oil and temperature data and acting before it happens.

The tensile force in the bolt produced by tightening. Preload is what actually holds the joint, not the torque itself.

A non-contact position detector, used for rotor lock, hatches and limit sensing.

A sensor measuring temperature through resistance change. Standard for bearing and winding temperatures.

The maximum power the turbine can hold continuously. 2,500 kW for the N90.

The wind speed at which rated power is first reached. Above it, pitch holds power constant.

The non-working component of power exchanged to support grid voltage, measured in kVAr.

A signal-level switching and protection device.

A reset done from SCADA without going to site. Some alarms are locked out of it.

The rope system used to lower an injured worker down the tower. Every team must carry one.

Clearing the alarm and returning the turbine to production. A reset without a cause found will repeat.

Identifying hazards and controls in writing before work starts.

The work of finding the real cause of a failure. The only way to stop it repeating.

The rotating assembly of blades, hub and spinner. This is what converts the wind's kinetic energy into rotation.

The pin that mechanically stops the rotor turning. It goes in before anyone enters the hub.

The hardwired circuit with every critical safety contact in series. If any one opens, the turbine stops.

The system for monitoring and commanding every turbine on site remotely. Production, alarm and trend data live here.

Planned maintenance on a calendar, usually packaged into six and twelve month services.

A serrated add-on fitted to the trailing edge. It lowers aerodynamic noise.

The small crane inside the nacelle. Good for tools and parts, not for major components.

The single-person lift inside the tower. The ladder still counts as the escape route.

The operating mode a turbine is put in for maintenance. Remote commands are disabled.

The target value a control loop is trying to reach.

The strobing shadow cast by a turning blade. It is a planning constraint near housing.

The vertical internal wall joining the two spar caps. It carries the shear load.

The brush and ring assembly that carries power and signals between the rotating hub and the fixed nacelle. Carbon dust build-up is a classic fault.

The total acoustic power the turbine emits, in dB(A). It can be turned down in a night mode.

The main composite band inside the blade that carries the bending load. The spine of the blade.

The aerodynamic cover over the hub. Everyone calls it the spinner; you climb through it to service the pitch system.

Flow separating from the blade when the angle of attack gets too large. Lift drops, drag rises.

The circle the rotor sweeps. Power scales directly with it: 6,362 m² on an N90.

The cabinet holding the medium voltage breaker, disconnector and instrument transformers, at the tower base.

Finding loose connections and hot spots in cabinets from a heat image.

A temperature protection element embedded in a winding. It stops the motor on overheating.

Tightening a bolt to a specified value. The manufacturer's figure always governs.

The angle of the main shaft to horizontal, about 5 degrees. It increases blade-to-tower clearance.

The linear speed of the blade tip. Onshore it is usually capped near 80 m/s because of noise.

The ratio of blade tip speed to wind speed. Modern machines run best between 7 and 9.

The short safety briefing held before starting work, covering the day's risks.

The tapered steel shell that lifts the rotor to where the wind is strong and steady. Usually erected in three to five sections.

One piece of the tower, bolted to the next through a flange. Transport limits decide how long a section can be.

The sharp rear edge of the blade. Most of the aerodynamic noise comes off it.

The transformer that steps generator voltage up to medium voltage. It sits at the tower base or inside the nacelle.

The time-stamped record of measurements. Root cause usually shows up in the trends.

The variation in wind speed relative to the mean. High turbulence drives fatigue loads and failures.

The twist built into the blade from root to tip. It keeps the angle of attack right at every station.

The battery-backed supply that keeps the control system alive when mains is lost.

Finding bearing and gear damage from the vibration spectrum.

Small fins bonded onto the blade. They delay flow separation and can add a few percent of output.

The slowing and added turbulence downwind of a turbine. It cuts the output of machines behind it.

The statistical model describing how wind speeds are distributed at a site, defined by shape k and scale c.

The polar chart of how wind is distributed by direction. Turbine layout is planned from it.

The increase of wind speed with height. It means the upper blade sees faster wind than the lower one.

The vane that measures wind direction. It is the reference for the yaw system.

One of the GWO basic modules, covering tower climbing, equipment use and rescue.

The large toothed slewing bearing between nacelle and tower. Its teeth are grease lubricated.

The calipers that hold the nacelle once it reaches its target heading. They apply partial pressure while yawing.

The geared electric motor that produces yaw movement. A turbine may carry four to eight of them.

The nacelle sitting off the true wind direction. Even a few degrees costs measurable production.

The system that turns the nacelle into the wind: motors, ring gear, yaw bearing and brakes.