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What is a Permanent Magnet Generator?

A permanent magnet generator is a device that converts mechanical energy to electrical energy. In this device the rotor windings have been replaced with permanent magnets. These devices do not require a separate DC supply for the excitation circuit or do they have slip rings and contact brushes. These machines are superior alternatives to traditional induction motors that can be coupled with turbines, diesel generators and used for hybrid vehicles. Another major advantage is that these machines does not require any specific work environment and hence can be used in wind and water machines.

The PMG can be a DC voltage machine with brushes and rotary collector or much more frequently an AC synchronous multiphase machine whereas the stator and rotor magnetic fields are rotating at the same speed. 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. If you are considering a permanent magnet DC generator then the inductor will be found at the stator with an array of permanent magnets. But in case of an AC generator the inductor is located at the rotor with an assembly of permanent magnets.

A PMG reduces loses in the rotor by 20 to 30 percent. Thus we get a much cooler system. This temperature reduction also reduces the temperature of the bearings and hence improves the reliability and the lifetime of the bearings. Recent developments in PMG technology have been made possible by a significant improvement of the magnetic materials during the past decade. A little piece of Neodymium Boron Iron (NeFeB) is 10 times stronger than the traditional ones made from ferrite magnate. Thus with further research we can improve the strength and reliability of these devices.

The demand for these devices is increasing day by day. With the increasing cost of electricity people are looking for an alternate source of energy and the permanent magnet generator perfectly fits in that place. These devices do not use any environmental resources to produce energy and thus are environment friendly. Besides no wastage or by products is generated from these device in the process of energy generation. Environment experts recommend the use of permanent magnet generators as these can reduce the impact of pollution by up to 50%.

ALXION manufactures 3 phase permanent magnet alternators, see STK Alternators range.

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