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In this paper, the influence of stator teeth deformation on electromagnetic force and acoustic noise of claw pole alternators was investigated. The characteristics of stator teeth deformation caused by welding and assembly were first illustrated, and the influence of stator teeth deformation on the frequency and spatial order of electromagnetic force harmonics was deduced analytically. Then the electromagnetic forces of three alternators with different stator teeth deformation types were simulated by the finite element method, and compared with the electromagnetic force of nominal alternator. In addition, a multi-physics simulation model was established and the electromagnetic noise of the above three different stator teeth deformation alternators was calculated. Finally, the changes in phase current and output current of claw pole alternator with and without stator teeth deformation were analyzed. The analysis results were verified by back-EMF bench test and noise bench test. Results showed that although stator teeth deformation would not change the frequency components of the electromagnetic force, but would generate additional electromagnetic force harmonics. When the number of deformed teeth was not an integer multiple of the rotor pole-pair number, the electromagnetic force harmonics with extra spatial order would appear. [ABSTRACT FROM AUTHOR]

This paper proposes a novel simulation method to analyze the characteristics of the electromagnetic noise of claw pole alternators under stator winding interturn short circuit faults. For the two types of faults: short circuit between two wires of the same phase and short circuit between turns of the same wire, a general circuit model built in Matlab/Simulink was introduced to obtained the phase current and output current signals. The phase current was then used as current source and the claw pole alternator was simulated as an electric motor rather than a generator to analyze the magnetic force and electromagnetic noise by using 3-D finite element method and boundary-element method, respectively. A noise bench test was conducted to verify the simulation results. It is shown that under the stator winding interturn short circuit faults, the output current harmonics and electromagnetic noise of the three-phase 12-pole/36-slot claw pole alternator would increase greatly. The 12th order noise replaces the 36th order noise as the most dominant order noise at low speed. The method proposed in this paper can also be used to diagnose the stator winding interturn short circuit faults of claw pole alternators. [ABSTRACT FROM AUTHOR]

The electromagnetic noise of a claw pole alternator is minimized by rotor claw chamfering in this paper. Taguchi method was first applied to evaluate the importance of all of the six chamfer parameters on the output current and the main magnetic force harmonic, and three strongly influential parameters were later selected. Subsequently, the mathematical models of the output current and the sound power level with respect to the three chamfer parameters were developed using the response surface method. Finally, the three parameters were further optimized using the genetic algorithm. A prototype of the optimally designed claw pole alternator was manufactured and its performance was tested. Results show that the rotor claw chamfer does not decrease the output current but can reduce the noise significantly. The sound power level is decreased by more than 15 dB(A) after optimization. The trailing edge chamfer is better than the leading edge chamfer regarding noise reduction. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of the electromagnetic noise radiated by an external rotor in-wheel motor (IWM) are investigated with the Doppler effect taken into consideration. First, Maxwell stress tensor method is employed to derive electromagnetic forces on the magnet surface. The effect of common current harmonics is also analyzed. Then, a structural model of the rotor is built and modal test is conducted to validate the model. Nodal forces, which are calculated by finite element method, are transferred from the electromagnetic mesh to the structural model for further vibration prediction. Finally, boundary element method is used to calculate the noise radiated by the rotor. In particular, the Doppler effect is considered. The calculated results are validated by the noise test. It is found that the end cap contributes more to the overall noise than the shell, and obvious sound directivity appears in the noise of the IWM. The noise measured perpendicular to the outer end cap is larger than that measured in other directions. In addition, the Doppler effect would induce additional side-frequency components around high-frequency peaks in the external rotor motor. [ABSTRACT FROM PUBLISHER]

A multiphysics model is proposed to predict electromagnetic noise and analyze sound quality of permanent magnet synchronous motor with a variable speed range. First, a two-dimensional electromagnetic finite element model is built and the current during run-up is tested to serve as the input of the model for force calculation. The force is transferred to structural model and the mode superposition method is used to predict vibration. Then, based on the structural mode information and acoustic transfer vector, noise transfer function between electromagnetic force and sound pressure is established. A balanced efficiency and accuracy of noise calculation during run-up is achieved with this function. Finally, psychoacoustical indices are calculated to evaluate the sound quality with the influence of current harmonics into consideration. The calculated vibration and noise are experimentally validated and the errors of noise level in the whole speed range are all below 4 dB. It is also concluded that current harmonics greatly deteriorate the sound quality. [ABSTRACT FROM PUBLISHER]

This paper first derives the characteristics of radial electromagnetic force considering different types of current harmonics. By using two-dimensional fast Fourier transform, the force calculated by the finite element method is decomposed to obtain the frequencies of the force components in specific spatial order. Then, a multiphysics model for electromagnetic vibration and noise calculation is proposed. A modal test is implemented to validate the equivalent stator model and the nonuniform distribution of electromagnetic force acting on the teeth surface is taken into account through the nodal force transfer method. The calculated vibration and noise agree well with those obtained from experimental test. Finally, vibration and noise under different supply currents are investigated, and the variation patterns of the noise and vibration peaks are explained by the amplitude changes of the lowest spatial order force due to current harmonics. It is found that the influence of current harmonics on vibration and noise depends on their effect on the lowest spatial order force, and in order to figure out this effect, the phase angle, phase sequence, and frequency of current harmonics should all be considered. [ABSTRACT FROM AUTHOR]