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Kendrion N.V.

Kendrion N.V. is a public limited liability company incorporated under the laws of the Netherlands, with its registered office in Zeist.

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Wind turbine

Permanent magnet brakes for

Renewable energies

Especially for the field of energy technology Kendrion offers permanent magnet brakes which are robust, low-maintenance and excel by low energy consumption.

Renewable energies

Kendrion is a manufacturer of electromagnetic components for energy technology applied in particular in the field of wind power stations.
Especially for the field of energy technology Kendrion offers permanent magnet brakes which are robust, low-maintenance and excel by low energy consumption.

Drive systems for wind turbines-
Permanent-magnet brakes for pitch control in wind turbines

Meeting high energy requirements worldwide whilst reducing the associated carbon dioxide emissions – one of the main causes of global warming – is a major challenge which can only be tackled through strong and committed efforts. The increasing use of renewable energy sources, especially wind power, is a crucial factor for achieving these objectives. By improving the output capacity of the individual wind turbines, the number of required system installations can be reduced. With the growing share of renewable energy sources in covering the total energy requirements, the strong weather-dependent variations in the wind energy yield have become an increasingly pressing issue. In addition to increasing the installed rated output capacity of all wind turbines, ensuring a mostly uniform energy yield throughout the day is a key factor to mitigate output variations. To achieve this, wind turbine manufacturers opt for individual power output control of wind turbines through active pitch control of the rotor blades. With this solution, the power output of wind turbines can be collectively controlled according to actual electricity requirements and based on the actual wind resources available at a given time. Moreover, another factor to be considered is that the material stress to the rotor blades caused especially at high wind speeds must be kept below the rated stress limits. This means that in stormy weather the rotor blades must be pitched out of the wind and kept in a braked position. All these requirements in terms of higher output capacity, uniform energy yield and enhanced safety raise new and increasingly complex challenges for wind turbine manufacturers. Active pitch control is implemented by means of electric drives that are coupled with electromagnetic brakes. Once the optimum wind turbine power output has been adjusted by the pitch control system based on the available wind resources and the energy requirements at a given time, the electromagnetic brake keeps the rotor blade at the desired pitch angle. This means the motor is not required to transmit any torque and can be unpowered. Moreover, the brake also ensures that the rotor blade is not turned into the wind accidentally during high-wind periods, which would cause excessive structural loads or breakage of the rotor blades. Kendrion Industrial Drive Systems boasts many years of in-depth experience as an industrial solution provider of brakes for electric motors used in a variety of applications, among which rotor pitch control systems in wind turbines. For this specific application, Kendrion has developed a Cold Climate Version (CCV) of its permanent-magnet brake to provide a special solution designed to ideally meet the wind power requirements of onshore and offshore wind farms. The continuously increasing demand for this type of brake from the wind power industry confirms its unique quality. The permanent-magnet brakes satisfy the most exacting holding torque requirements even in adverse weather conditions in summer or winter at temperatures of between -40°C and +70°C and strong humidity variations. Owing to the use of high-quality brake components, Kendrion meets even the most stringent requirements of the wind energy sector in terms of the reliability of all individual component parts. Excellent functional reliability and minimum idle time give wind farm operators outstanding cost-effectiveness of their wind turbines, even if their installations are located in remote or difficult-to-access areas.

Functional principle of permanent-magnet brakes

Compact dimensions and relatively low weight are among the key benefits of permanent-magnet brakes. The power density resulting from the use of permanent magnets is about twice the density of spring-applied brakes. Sophisticated qualification and testing procedures enable Kendrion to guarantee maximum torques. During motor rotation, the special design of the permanent-magnet brake ensures reliable brake release with zero residual torque. This eliminates wear during operation and ensures an exceptionally long lifecycle. Moreover, unlike with spring-applied brakes, permanent-magnet brakes remain unaffected by the centrifugal forces generated during rotor rotation. In spring-applied brakes, the friction disc contact with the friction partner located on the external side with respect to the axis of rotation of the rotor becomes stronger, thus causing increased unilateral wear during starting. This start-up wear may significantly reduce the brake lifecycle.