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NEW PERMANENT MAGNET GENERATOR OFFERS HIGH OUTPUT FROM SMALL SIZE
ABB has launched a new generator for wind turbines based on permanent magnet technology. Compared to a traditional machine, the new generator offers high output relative to the frame size, making for instance a 3.6 MW unit a full frame size smaller. The new generator can be operated in a wide speed range with a maximum output of 3.6 MW from a 500 mm frame. The efficiency is better than 98%. The design is based on ABB's low speed permanent magnet generator technology, launched last year. This has now been further developed with a more robust rotor suitable for higher speeds. The permanent magnet generator is a synchronous machine where the rotor windings have been replaced with permanent magnets. This eliminates the excitation losses in the rotor, which otherwise typically represent 20 to 30 percent of the total generator losses. The reduced losses also give a lower temperature rise in the generator, which means that a smaller and simpler cooling system can be used. The temperature reduction in the rotor also reduces the temperature in the bearings, improving reliability by increasing the lifetime of the bearings and the bearing grease. The high efficiency of the generator means better utilisation of the wind energy, producing more electrical power. The reduction in size and weight also makes the construction of the windmill easier as smaller lifting equipment can be used. Recent developments in permanent magnet generator technology have been made possible by a significant improvement of the magnetic materials during the past decade. A piece of neodymium boron iron material can have a magnetic force more than 10 times stronger than a traditional ferrite magnet.
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