Permanent magnets provide greater efficiency in wind energy

Permanent magnet generators improve the financial performance of wind power projects and are the answer for turbine manufacturers, who are looking for a powertrain that offers high efficiencies with partial load, greater availability and a simplified grid connection that protects the generator from any type of disturbance.

These permanent magnet generators, too, can be applicable to direct drive, medium speed and high speed systems.

A common view is that permanent magnet generators are applicable only to direct drive offshore wind turbines, where their use eliminates the potentially problematic gearbox. However, permanent magnet generators offer so many compelling advantages that they are now being designed as gearbox transmissions to operate at a wide range of output speeds.

Permanent magnet generators replace double feed induction

Dual-powered induction generators have provided the wind power industry with many years of excellent service. However, the number of undeveloped Class I wind sites decreases with each passing year, while project developers demand improvements in plant reliability and availability.

In this regard, permanent magnet generators offer a wide range of performance advantages to wind farm developers and operators that can make a significant and positive difference to project economics.

For example, permanent magnet generators are incredibly flexible. Your design can be customized for:

• Optimise the performance of the complete wind turbine powertrain.

• Speed, efficiency, weight and cost are four fundamental and interdependent factors that can be varied to meet the objectives of the wind turbine OEMs.

• The permanent magnet generator designer can exchange the properties and weights of magnet, stator copper and stator lamination to achieve the required objectives without the need for the turbine OEM to accept a standard, market-optimal, non-optimal generator.

Permanent magnet and rare earth generators

The magnets in the rotor of a permanent magnet generator use rare earth metals. The magnets used in these generators generally contain ~ 30% Nd (neodymium) in weight, and most of the remaining weight is made up of low-cost ferrous materials.

Permanent magnet generators are flexible. They allow wind turbine designers to consider powertrains with a wide range of topologies, from conventional modular gearboxes and generator arrays to fully integrated systems (or hybrids) assembled within a single cabinet, and even direct drive systems that operate without a gearbox. Every topology has merits.

In addition, a conventional high-speed drive train with fully independent or modular gearbox and a permanent magnet generator appears in the layout of the modular drive train.

This gives the turbine OEM the maximum flexibility to select the suppliers of the gearbox and generator, as both are completely independent.

Finally, by integrating some components of the powertrain, the overall length and weight can be significantly reduced. This is achieved by combining the main bearing and gearbox for a medium or high speed shaft design, or by close coupling of the gearbox and generator as shown in the integrated powertrain layout.

All these features of permanent magnet generators make it possible to reduce costs in wind energy. If you want to know more about this technology, at IMA we can advise you on the magnetism solution that best suits your project. If you have questions, you can contact us.