Wind Turbine Research and Teaching Laboratory


In the small wind industry there are two main types of turbines: grid tied machines with a constant rotor speed, and inverter based machines with variable speed permanent magnet generators. The benefit of grid tied, constant speed machines is that they don’t need an inverter, which can be costly and unreliable. The drawback is that there is only one wind speed where constant speed rotor aerodynamics are optimized, and wind speeds can vary over a large range. Below or above that optimal wind speed the constant speed rotor is less efficient and turbine performance suffers. Inverter based machines can speed up or slow down their rotor (optimizing it aerodynamically) by varying the load on the inverter.

IIT's DOE-sponsored wind turbine incorporates a proprietary continuously variable planetary (CVP) gearbox in order to have both benefits. It can use a grid tied induction generator without the costly and unreliable inverter, yet it can still optimize the rotor aerodynamically by speeding up and slowing down the rotor mechanically. Since the induction motor speed is held to within a small range based on slip speed, the term “ratio” is used to describe the CVP output speed to input speed. A ratio of 2.0 means that the rotor side of the CVP is spinning at half the generator speed, and a ratio of 0.5 means that it is spinning twice as fast.

The Viryd Test Stand consists of two main halves: the turbine side and the drive side. The turbine side of the test stand contains the entire Viryd turbine driveline, with the addition of a torque transducer. This is the same drive that is employed in the field unit at IIT. The drive side consists of a drive motor, gearbox, torque transducer, and inertia wheel, which together are used to realistically simulate the rotor. This setup can be used to simulate wind profiles in a controlled environment over a shorter period of time.