**Author details**

These forces are very high and are a major problem in bearing design. The axial force on the bearings is equal to the resultant force exerted on the stator, i.e. 76 kN. This problem exists

The operation of the speed multiplier is of synchronous type, with no possibility of direct control, so there is a risk of stalling one rotor relative to the other. A precise study of this phenomenon is yet to be done (because, oddly, there is nothing definite on this subject in the

In the absence of a comprehensive study, the main solution to this problem in the design of the wind system is to monitor the electrical angle, ψ, between the magnetic fields from the two rotors through position sensors placed on the two shafts, or by indirect measurement

When ψ tends to become greater than 90°, especially during rapid changes in the mechanical power from the wind turbine due to gusts, it is possible to influence the level of electrical power delivered by the generator in order to act on the dynamics of the driven load, allow‐

However, the system becomes more stable as the maximum torque level transmitted by the multiplier is distanced from the maximum torque absorbed by the generator. This necessari‐

The consequences of a possible stall are not really problematic for the intended application, provided that there is an electrical method of slowing down the wind turbine to allow me‐

The addition of electrical conductors at the high speed rotor, intended to act as electrical shock absorbers and allowing the transmission of high asynchronous torque, makes the op‐

It has been shown that a system combining a magnetic speed multiplier and a high-speed generator is an interesting alternative to the use of a direct drive generator. The high per‐ formance level of the magnetic gear discoid structure allows the design of a more compact

In this context, despite its limited capacity in the transmission of torque, the magnetic speed multiplier has many advantages over its mechanical counterpart, but the cost will inevitably

through the voltage produced by a detection coil placed at the magnetic teeth.

in most discoid machines and hampers their development.

bibliography). It goes without saying that this issue is delicate.

ing it to follow more easily the variations in speed.

ly leads to oversizing of the speed multiplier.

chanical braking or pitch control of the blades.

be higher because of the use of expensive materials.

eration safer.

**7. Conclusion**

system with better efficiency.

**6. Stability in operation**

264 Advances in Wind Power

Daniel Matt1 , Julien Jac2 and Nicolas Ziegler2

1 Institut d'Electronique du Sud - Université Montpellier 2, Montpellier, France

2 Société ERNEO SAS, Cap Alpha, Clapiers, France
