This paper studies the application of fractional slot winding for permanent magnet synchronous generators, which are being widely used in wind turbine systems. A 3kW axial flux permanent magnet synchronous generator is chosen when studying the winding design. The fractional slot winding is studied first in terms of number of periodicity of machine, the greatest common divisor of N_s and N_p, period of cogging torque, the winding factor by using star of slots. The machine is then designed with both fractional slot 12/10, 18/16, 18/20 and 24/20 and integral slot 30/10, with same electric loading and magnetic loading, resulting in similar machine dimensions. Parameters including phase resistance, back-EMF and inductance of candidate slot/pole combination are calculated and compared. The influence of winding design to performance of PM generators is studied when generator is connected to a diode rectifier or forced-commutated rectifier. The performances are evaluated in d-q coordinates and compared with integral slot winding (q=1).
This paper describes an investigation into the reduction of vibration and acoustic noise in switched reluctance motor. The vibrations of electric motors are mainly determined by two factors, radial force excitation and structure borne transfer function. The radial force, which is the dominant source of vibration, was analyzed analytically first. Based on the analysis, it was derived that vibration could be reduced by increasing electrical constant time and delaying radial force falling time. Modal analysis was carried out on precise mechanical models of prototype motor in three dimensional finite element method (3D FEM) software to study the structure borne transfer function. Experiments were set up and the results verified the analytical and numerical results.
Axial flux permanent magnet generator (AFPMG) is can have one or two sided stator windings, meaning that the rotor disc of which the permanent magnet (PM) are mounted may be sandwiched in between two parallel stator discs. This paper deals with the development of AFPMG for a gearless wind energy system. This gives the axial air gap PM generator the potential for very high torque generator applications. The design, construction and test results of 3kW, 240rpm AFPMG are presented. The electromagnetic analysis was carried out by three dimensional finite element analysis (3D FEM) method and the thermal field analysis was computed by the computational fluid dynamic (CFD) method. Based on the analytical design approach, a 3kW prototype generator is constructed. The predicted performance values from the analytical model are then compared with experimentally measured quantities to evaluate the effectiveness of the analytical design approach.
토끼의 프리모 순환계(경락순환계로 불리움)의 연결망을 표시하기 위해, 형광 나노자성입자의 유체와 안정되게 혼합시킨 알시안블루 용액을 토끼의 복대정맥 근처의 림프노드에 주입하였다. 림프노드에 혼합 염색액을 주입한 후, 림프관 내부 프리모관의 색이 진한 청록색으로 표시되었다. 림프관 내부에 떠있는 프리모관 존재를 확인되었고, 채취된 림프관과 프리모관을 체외에서 생리식염수를 패트리디쉬에 담아 놓은 후 영구자석의 수평 운동에 따라 프리모관의 주기 운동을 사용하여 자기적 특성이 관찰되었다. 분리되어 채취한 프리모관의 휘어짐 정도는 알시안불루와 형광 나노자성입자를 흡착한 프리모관 내부를 통과하는 자기장의 세기에 의존함을 알 수 있었다.
This paper proposed a method to compensate the unbalanced magnetic force in 12/8 switched reluctance motor. Using two-dimensional transient finite element analysis coupled with external circuits, both motor and inverter could be modeled to study the performance of motor. Airgap nonuniformity caused by eccentricity between the stator and rotor axes was found to be the main source of unbalanced magnetic force. Several connecting methods of coils were studied and it was observed from the simulation results that the currents could be adjusted in certain parallel paths and unbalanced magnetic forces could be reduced. The effects were also verified by experiment results.
This paper investigates eddy-current in an axial flux permanent magnet (AFPM) machine, which consist of the segmented stator teeth and concentrated winding, with one inner rotor and double stators. Analytical methods was developed to calculate the eddy-current loss of PMs and other solid components, including effect of winding harmonics and permeance variation due to slot opening. Eddy-current losses were analyzed by time-stepping three dimensional finite element analysis (3D FEA) in two rotor models, when magnets are insulated or noninsulated. A prototype machine was manufactured based on analysis results, and was tested as a generator. It is found that rotor stainless PM holder should be used in order to reduce eddy-currents and insulation of PMs further reduces eddy-current losses.
This paper presents dynamic characteristics in Switched Reluctance Motor (SRM) with rotor eccentricity and proposes the reduction method of rotor eccentricity effects by the different winding connections. These characteristics investigations are computed by 2D transient magnetic FEM analysis coupled with external circuits. The radial and unbalance magnetic force in the stator, which is the main exciting force of the vibration, is calculated using Maxwell stress method and compared with the performance characteristics according to the serial and parallel connections of windings. The influence of winding method counteracting unbalance forces on the rotor vibration behavior is estimated by the current waveforms of the paralleled paths under rotor eccentricity.
The axial flux permanent magnet (AFPM) machine is widely used in many applications due to its advantages. But the conventional AFPM machine has the major problem such as the deformation and unbalanced air gap occurred because of the large magnetic attraction force between the rotor and the stator. For these problems, the magnetic attraction force must be accuractly calculated in the process of the design step of the mechanical parts. Thus, this paper proposes the analysis method to compute the magnetic attraction force of AFPM machine considering a unbalanced rotor structure. The quasi 3D model with a different air gap condition is introduced to analyze the magnetic flux density and the magnetic attraction force due to the eccentricity of rotor structure. To validate the proposed analysis process with the quasi 3D model, 3D FEM analysis is performed to compare the results. As results, the proposed analysis results was obtained the similar results to 3D FEM analysis results. The proposed method is applied and estimated to the 130 kW AFPM generator.
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