This paper dealt with the investigation and implementation of the cogging torque reduction technique in permanent magnet generators with a fractional slot stator/rotor combination of 24 slot/18 pole structure. A novel of cogging torque technique in a permanent magnet generator was developed and proposed in the paper. In the study, the cogging torque reduction technique was based on the compounding of two cogging torque reduction techniques, i.e., the magnet edge shaping with dummy slotting in the stator core of the fractional slot number. By employing the CT reduction technique proposed, effects on the decreasing of tangential flux density in the air gap of the permanent magnet generator, while the normal flux density almost remained constant. The tangential flux density is one important parameter regarding the peak of cogging torque in permanent magnet generator or other electrical machine structure. The normal and tangential flux have been analyzed. The cogging torque of the permanent magnet generator was analyzed and presented in the paper. By compounding both cogging torque reduction techniques, i.e., magnet edge shaping and dummy slotting in stator teeth have been expected to achieve the cogging torque reduction. The electromagnetic performance of the permanent magnet generator was performed using a finite element analysis of FEMM 4.2. It has been proved that by combining of magnet edge shaping and dummy slotting in stator teeth can reduce the cogging torque of permanent magnet generator significantly. It has been found that the cogging torque reduction for the proposed structure around 98.08 % compared with the initial structure.
Cogging torque is one important problem in a permanent magnet generator. With a good understanding of the phenomenon, the cogging torque can be minimized by using the multi-objective technique. This paper presents a combination technique for cogging torque reduction by an appropriate small stator slot opening width, stator shoe height with fractional technique in Permanent Magnet Generator. Cogging torque waveforms, along with other relevant characteristics are investigated in this research and by analysis using the finite element method, the combination width shoe height and magnet edge slotting effect to decline the cogging torque peak value. A significant value of cogging torque, when slot opening width of 1.55 mm and shoe height of 2.3 mm, provide the peak value of cogging torque in the structure is 0.00062 N-m for positive value and about -0.00064 N-m for the negative value. It can be concluded that this type of slot opening width of 1.55 mm and shoe height of 2.3 mm is the best structure of the fractional 8 slot, because it has any significant low of cogging torque and least of unbalance magnetic pull
In this study, the effect of dummy slot in stator core and magnet in rotor core greatly affects the value of the cogging torque reduction in permanent magnet machine. The structure of permanent magnet machine was analysed employed finite element based on the finite element method magnetic (2D). In this study, 4 type of permanent magnet machine structure has been analysed. Permanent magnet machine structure in rotor have 4 type design magnet, permanent magnet machine with initial structure magnet, bread loaf, magnet edge slotting, and magnet edge slotting-magnet slot of surface. The cogging torque reduction of the proposed permanent magnet machine were computed and compared with the initial structure. Using the finite element, authors have computed and found that the cogging torque reduction of type 3 and type 1. The cogging torque of proposed permanent magnet machine could be reduced to 97.17% by employing the dummy slot in stator core.
Cogging torque generated in permanent magnet machine effects to some undesirable vibration and noises. In order to minimize the cogging torque in permanent magnet is the most important issues recently. This paper investigated the influence of the value of height and length of slotting in magnet edge on the cogging torque reduction. For purpose of study the structure of 24 slot/10 pole of permanent magnet machines have been chosen. The 2-D finite element based on FEMM 4.2 software was implemented to compute the permanent magnet machine performance. Simulation results showed that by optimising the height and length of slotting in magnet edge can reduce the cogging torque of permanent magnet machine significantly. The most effective way by employing a-two step slotting with 2.5 mm of height and 0.7 mm of length of the slotting in magnet in the first step of slotting. In the second step of in magnet edge, the length of slotting has been assigned as much as 2.3 mm and the height of slotting was 0.588635 mm. By employing the FEMM, three of different magnet structures of permanent magnet machine were analysed. It was found that the cogging torque of permanent magnet machine proposed magnet structure as much as 99.7 % compared with the initial structure of the permanent magnet machine.
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