Analysis of a multipole, low-speed permanent-magnet synchronous machine

The study deals with the design and the analysis of a multipole, low-speed permanent-magnet synchronous machine. High energy NdFeB magnets are mounted on the surface of the rotor yoke. The machine can be used as a generator in gearless wind turbines or as a machine in other low-speed applications. The electromagnetic optimisation of the machine is done by a genetic algorithm combined with the finite element method. The rated power of the machine is 10 kW for the rotational speed of 175 rpm. The stator winding can be divided in several parallel parts and, therefore, the machine can also be used with different rotational speeds. The demagnetisation of the magnets is not a problem during a three- or a two-phase short circuit The prototype machine has moderate torque ripple and high efficiency, furthermore, the voltage waveform is almost sinusoidal. The calculated results correspond well to the experimental results.