Wind and tidal turbines

Drive train of WT in most cases include a gearbox and a generator (Fig.1,a). The gearbox and the generator can be mechanically integrated (Fig 1,b).

(a) (b)

Fig.1. Wind turbines with gearboxes.

Direct drives are usually bulky and heavy (Fig.2). There are, though, special designs usually based on integration with the WT structure (Fig.2,b), in order to reduce weight. In DriveConstructor we focus on geared solutions only.

(a) (b)

Fig.2. Wind turbines with direct drives.¹

Load characteristics

There is theoretical maximum power which is possible to extract following the maximum torque curve shown in Fig. 3-4.

It can be seen that generator speed increases in Region II and is kept almost constant in Region III. However, there should be kept some speed reserve (between $n_1$ and $n_2$ in Fig.5) for the overspeed case due to wind gusts.

Fig.3. Generator RPM vs torque. ² Fig.4. Wind speed vs RPM and power. ³ Fig.5. Turbine load curves.

Parameters of wind (or tidal) turbine

• Rated speed of the propeller (above this speed maximum energy is extracted)
• "Cut off" speed, which is maximum allowed speed (turbine and generator are not run above this speed)
• Rated torque (at this torque maximum energy is extracted)
• Extra torque (torque margin) is needed to prevent runaway of the turbine in case of wind gusts and very strong wind in general.

¹ Source of the picture ² Source of the picture ³ Source of the picture