Application of magnet grouping technique in open slotted axial flux permanent magnet synchronous alternator

In our world, there has been a tendency towards renewable energy resources due to the reduction of fossil fuel reserves, the monopoly of certain countries, the increase in energy demand and the increase of environmental pollution. One of these renewable energy sources is wind energy. Until this day, transferring the motion from the propeller to the alternators with gear systems bring about the large volume of wind turbines and requiring constant maintenance. Alternators have been developed which can be connected directly to the propeller shaft in order to eliminate these problems. The Axial Flux permanent Magnet (AFPM) machines, which have been studied since the 19th century, have found limited application due to their low power density. After 1980, significant developments in magnet technology have taken place. Thus, instead of winding in the rotor, high magnetic flux magnets (NdFeB and Sm2 Co17) have started to be used. Thus, there was an increase in yield due to the lack of copper losses from windings in the rotor. Today, Axial Flux Permanent Magnet Machines has become a frequently used machine with advantages such as small volume and weight, low losses, high weight / torque ratio and high power. Besides the important features that AFPM machines have, there are some disadvantages. The cogging torque is the most important one. Breaking moments that occur as a result of the interaction between the edge of the slotted and the magnet are called the cogging torque. The use of open slotted of AFPM machines significantly reduces the production cost and increases the quantity of cogging torque considerably. In AFPM machines, many methods have been given in the literature to eliminate the cogging tork. These methods are basically divided into two. The first is the techniques on the rotor side and the second is the stator side. Rotor side techniques are more suitable for production costs. The major ones are: magnet shift techniques, rotor shift at double-rotor systems, using different spring length magnets in both rotors, rotating the magnets around an angle, use of different types of magnets and magnet grouping. In this study, a magnet grouping technique has been proposed to reduce the cogging torque of an open slotted axial flow permanent magnet (OSAFPM) alternator. By forming an experimental apparatus for the suggested technique, experimental data were obtained for 2,4 and 6 grouping. In the literature, only two-grouping technique is mentioned. The studies were limited to simulation. Therefore, with this study, the effect on alternator performance was investigated by using different number of groupings in order to eliminate the big cogging torques occurring in the alternator with open gutter structure. As a result of the experimental studies, it was concluded that the magnet grouping technique was effective for the cogging torque and harmonic distortion. At the same time, as the number of grouping increases, it has become clear that there should be a decrease in the number of angle between groups. Besides, in groupings 2, 4 and 6, the optimum angle values were 34, 32 and 30 degrees, respectively.