| Popis: |
The aviation industry is in the process of developing the All-Electric-Aircraft through a succession of increasingly More-Electric-Aircraft. Through this evolution, previously pneumatically or hydraulically powered functions are being implemented by electrical systems. This requires an increase in electrical power generation and distribution. To meet this increasing demand at competitive power densities, a change of generator technology may soon be required. Permanent Magnet (PM) machines, due to their power density, efficiency and simple robust construction, are a strong candidate technology for future aircraft electrical power generation. A variable frequency AC system based around a non-salient PM machine and a parallel shunt regulator is assessed and analysed to examine the effect of generator electromagnetic parameters on the rating of the regulator. With the correct pairing of PM machine and converter, it is anticipated that a system could be conceived which provides the necessary performance to meet the coming needs of the evolving aerospace industry at a competitive mass density. Key to achieving an optimised converter is the realisation of a machine with a specific PM flux linkage and inductance. Surface mounted PM machines offer a robust and simple machine construction. This topology is often employed where electromagnetic saliency is not required. However, their design is currently constrained by the effect of rotor containment structures on the machine's magnetic circuit. Alternative containment materials with a degree of magnetic permeability are calculated to reduce the effective air-gap usually presented by the containment material. Cold-rolled AISI 304L stainless steel exhibits such magnetic propelties. A prototype rotor is constructed incorporating a containment sleeve constructed of this material in a laminated construction. The machine is then tested to verify the analysis and to demonstrate shunt regulation of a PM generator. A further investigation is then conducted to assess the suitability of salient machine designs for operation as shunt regulated generators before conclusions are drawn and suggestions for future research are proposed. |
