Anatomy of a Wind Turbine: Page 2 of 3


Inside this Article

Turbine head
Rotor, stator, diode rectifier, slip rings, and bearings exposed on a Bergey XL.1 1 KW generator.
Blade's airfoil
A cross-section of an extruded carbon-fiber blade shows the airfoil shape.
The stator from a 10 KW Bergey Excel showing multiple windings. A bearing in the center supports the rotor.
Slip rings, brushes, bearing
Slip rings and brushes, and yaw bearing assembly from an ARE wind turbine.
One feature of Southwest Windpower’s controller is to rectify the turbine’s AC output to DC for battery charging.
Before regulating
As the wind approaches this turbine’s rated speed for maximum power, the rotor begins to swivel out of the wind to prevent overspeed. (Before)
As the wind approaches this turbine’s rated speed for maximum power, the rotor begins to swivel out of the wind to prevent overspeed. (After)
Turbine head
Blade's airfoil
Slip rings, brushes, bearing
Before regulating

Shaft & Bearings

The shaft of a wind turbine carries both rotors—the blades and the rotating part of the alternator. The shaft is suspended in bearings, which are usually sealed permanently. They need to be designed to withstand all the stresses of supporting the blade hub and any vibration from the alternator. Bearings typically last five to ten years.

Slip Rings & Brushes

Wind generators yaw to face the wind, but the transmission wiring is fixed to the ground. This can be a recipe for twisted wires, especially at turbulent sites where the yaw bearing is very free-moving. Most modern turbines use copper alloy slip rings to connect the turbine wiring to the fixed wiring. The slip rings are usually mounted in the part of the turbine that is fixed to the tower top. A set of graphite brushes is mounted on the yawing part of the turbine. The brushes ride on the rings as the turbine yaws, and serve to connect the alternator to the fixed wiring.

Yaw Bearing

A wind turbine needs to be able to follow the wind, changing orientation each time the wind changes direction. The sealed bearing that supports the wind turbine as it swivels on its tower is called the yaw bearing, and the swiveling motion is called yawing.

Braking System

Braking, as distinct from governing, is the ability to stop the turbine when you choose to. This can be useful when there is a problem with the machine, when you need to work on it, or when you simply don’t need the energy. Manual braking is ideal, since it allows you to stop the machine in all conditions. Drum and disc brakes have been used in a few turbine designs, but most turbines use dynamic, or electrical, braking, where a big switch opens the connection to the grid or batteries, and shorts the three phases of the wind turbine together, making it very stiff to turn. Many wind turbines cannot be slowed by a short circuit once they are already running fast in high-wind conditions. Another method of control is manual furling—the ability to manually crank the tail over to furl the machine out of the wind.

Energy Transmission

Wiring routed down the tower carries the electricity generated by the turbine to the control room, usually as wild (varying voltage) three-phase AC. A few turbines rectify the output at the tower top, and transmit it as DC. Using thick copper wire reduces the risk of fire and limits power lost as heat. Where the wire run is very long, high-voltage AC transmission to a step-down transformer at the control room can be used to save on wire cost and energy losses. Batteryless grid-tied inverters work with higher voltages than most battery-based systems, so they lose less energy in transmission.


Some wind turbines use a plastic cover (cowling) spaced away from the alternator, which protects it from rain but allows airflow over the alternator for cooling. Many turbines have a separate nose cone, which serves an aesthetic purpose, as well as streamlines the turbine.

Comments (6)'s picture

The most efficient wind device ever conceived is the Mag Lev Vertical

Ian Woofenden's picture

I'm guessing that this idea/device is most efficient at separating dollars from investors (and perhaps homeowners) wallets.

The physics of vertical designs is not promising -- see and .

In addition, it's a mistake to put much focus on "efficiency" with wind turbines. They capture a free and abundant resource -- not a resource you have to pay for. So while capturing it more efficiently is useful, it's not as important as capturing it cost effectively. Hitting a specific efficiency number doesn't matter compared to what you pay for your kilowatt-hours over the lifetime of the machine.

And in the end, _reliability_ is the key measure of wind turbines. The "most efficient" wind turbine will make _very_ expensive energy if the machine only lasts a few months or years. The goal of wise wind turbine owners is a machine that reliably pumps out the kWh for years and decades. History shows that vertical designs and companies to not give this satisfaction. I recommend looking for products with a long track record, substantial warranty, and stable company that supports them.

Ian Woofenden, Home Power senior editor, and author of Wind Power for Dummies's picture

So do you even know What Vertical Axis Magnetic Levitation actually means?
cause if you did you know your statement is categorically wrong...
When you remove the bearings that ware out overtime, as well as the friction they intern create...
Why you can blow on the turbine with your own breath and make it spin...


Ian Woofenden's picture

There are many "brilliant ideas" that don't actually pan out in the real world of physics and business. While reducing bearing friction may be useful (though a minor factor), the bigger question is at what cost, and with what reliability. My experience -- and that of most long-time wind energy observers -- is that keeping it simple actually ends up making more kWh over the life of a machine.

A broken or very expensive machine that is "much more efficient" is actually not too useful. The bottom line is the cost per delivered kWh over the life of a real machine, not something that sounds like a good idea, but can't actually be purchased and operate for decades, providing energy to real people.

I'll continue to recommend tried and true machines from long-term manufacturers with warranty, support, and track record. The wind industry is full of distracting, time-and-money-wasting ideas and schemes. The real companies, products, and ideas last for decades and don't rely on hype or hyper marketing.'s picture

Oh I see.... it is that exact narrow mined thinking that has lead to no R&D into the subject matter in over 15yrs...
except one... little outfit not very well known Advanced Technology Industries (plural more than one Industry)
we have a 10mw system that will be deployed on the top of landfills as the "new standard" 4way hybrid Renewable Generation stations
worldwide starting July 2016

Shinning example of your defeatist attitude:
the electric car would have been the over welling car of choice on the highways today if what happened in 1992
never happened....i believe you get the picture...
Had Columbus listened to all those others saying you idiot...your gonna fall off the earth and never be heard from again...

Michael Welch's picture

Hi Solar Man. I suppose you are right, after many decades of either failed R&D involving vertical axis wind generators or the final products just not making it in the market for whatever reasons, my own views on the issue have been narrowed similar to Ian Woofenden's.

Home Power is not against research, but what we are against is touting technologies that aren't going to do what the customer needs. It's great to be excited about new possibilities, and that IS important to bringing new and successful technology to market.

But as a promoter of and a consumer of renewable energy technology, I flat out want stuff to work.

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