Effects of magnet topology on the harmonics of slotless-ironless axial flux permanent magnet generators

Summary form only given. This paper explores the effects of the shape and configuration of permanent magnets (PM) on the quality of induced voltage, and in particular investigates into how PM topology influences the output voltage of an ironless-slotless axial flux PM generator. It has been widely reported that the design of the magnets used in PM generators has strong bearing on the harmonic contents of the output voltage. High harmonic content results in higher losses and other adverse operational effects. The design procedure usually involves optimisation and trading off among a number of parameters, often made complicated by the structure of the machine. The unique ironless and slotless structure of the system under investigation, however, offers an distinct opportunity to establish a more direct relationship between magnet shape and generator performance. Two magnet shapes (with equal volume), namely semi-circular and trapezoidal, are studied. The effect of shape, and distance between the adjacent magnets of the generator, on the quality of output voltage are illustrated, which are predicted results by FE simulation. These predications are further validated by experimental results obtained from a prototype of the semi-circular magnet type running at 1650 RPM.