Авиационные генераторы с постоянными магнитами

Abstract

The capacity of aircraft generators reaches several hundred kV×A. For decreasing their specific mass, the generators are designed for limiting rotation frequencies in terms of strength considerations. With increasing the capacity of aircraft generators, their excitation system on the basis of high-energy permanent magnets can be regarded as an alternative to the electromagnetic excitation system. This is because the volume of magnets is several times smaller than that of ferromagnetic poles with windings. Therefore, permanent-magnet generators can be made with a rotor having a smaller mass and a shaft diameter several times larger than in a generator with electromagnetic excitation, due to which it becomes possible to increase their critical frequency and limit power capacity. In addition a rotor with permanent magnets has a higher strength and can be designed for higher rotation frequencies and for a larger number of poles than in case of using electromagnetic excitation. Permanent-magnet generators have higher efficiency values and higher overloading ratios. Rotors fitted with tangential magnets produce higher magnetic induction values in the air gap than the rotors fitted with radial magnets, due to which it becomes possible to make a high-frequency generator with a shorter length while keeping its mass almost unchanged. On the other hand, generators fitted with radial magnets have a stronger rotor and can be designed for higher capacities and rotation frequencies than generators with tangential magnets. Among many design arrangements of rotors, those with nonmagnetic yokes are the simplest ones, whereas arrangements with yokes made of gradient material are the most efficient ones. The most rational application of multipole permanent-magnet generators is in DC systems involving electronic converters.