Permanent magnet generator options for the More Electric Aircraft

This study has shown that a permanent magnet generator coupled with a PWM voltage source converter will adequately meet the LP shaft generator requirements for a future More Electric Aircraft. It also adequately satisfies the requirements for wide speed range control and fault tolerance, although it should be noted that full fault tolerance only seems achievable with a direct drive (nongeared) generator. The direct drive machine is suitable for either oil or air cooling, the oil-cooled option being smaller and lighter, even after taking into account the additional converter and cable weight arising from its increased reactance. The geared machine offers a net weight saving of 16% (compared with oil-cooled direct drive) but its fault tolerance is limited to open circuit faults and loss of drive in the power converter only. The study has firmly established the feasibility of permanent magnet generators for the More Electric Aircraft; however further work is required, most notably the estimation of rotor stray loss and the study of power system stability and protection.