Electromagnetic Force Harmonics Research Articles

Harmonic-Oriented Design and Vibration Characteristic Suppression for Interior Permanent Magnet Motors

In this article, a radial-electromagnetic-force-harmonic-oriented design methodology is proposed to suppress motor vibration. In the proposed methodology, the radial electromagnetic force harmonics innovatively act as the effective bridge between structural field and vibration performance. And avoiding low-order and large-amplitude radial electromagnetic force harmonics is the premise of designing low-vibration PM motors. For extensive investigation, a 36-slot/8-pole IPM motor with different winding configurations and variable rotor parameters is chosen as a design example. Then, vibration suppression methods of lowest-nonzero-spatial-order-shifting in the stator system and dominant-harmonic-amplitude-reduction in the rotor system are proposed. Next, the performances of the IPM motor are simulated for validating the proposed methodology. Finally, a prototype motor is fabricated and experimented. Both theoretical derivation and test results are presented to verify the validity of the motor and the proposed design methodology.

Fast Prediction and Staged Optimization of Electromagnetic Vibration in Permanent Magnet Synchronous Motor

The most common method to suppress electromagnetic vibration is to weaken the electromagnetic force harmonics (EMFHs), which are the vibration sources. Clearly, vibration is related to some other factors, too. Therefore, in this paper, modal analytical model and transmission function of a permanent magnet synchronous motor (PMSM) are studied, based on which a fast analytical method of predicting the electromagnetic vibration is proposed, so that the vibration can be preliminarily evaluated during the machine electromagnetic design. The time-consuming 3-dimensional finite element method (FEM) is not needed when predicting the vibration. Moreover, using the fast prediction method, a 15-dimensional multi-objective optimization problem for vibration, torque and efficiency performances is solved in stages. After optimization, the vibration is greatly reduced, and the torque performance is improved. The proposed methods are also proved to be applicable for different operating conditions and types of motors with various slot-pole combinations.

Vibration analysis of electric motors considering rotating rotor structure using flexible multibody dynamics-electromagnetic-structural vibration coupled analysis

AbstractIn this study, we develop flexible multibody dynamic-electromagnetic-structural vibration coupled analysis method to accurately predict motor vibration by considering the electromagnetic force characteristics, rotating characteristics of rotating motor motors, and their interactions at the no-load rated speed and operating speed range. The structural characteristics are accurately reflected by developing a three-dimensional (3D) finite element model considering the entire components of the motor. The reliability of the 3D finite element model of the motor is verified using the impact hammer test. In addition, to consider the rotational characteristics of the rotor structure, we develop a flexible multibody dynamics model that connects the flexible rotor and the bearing with revolute joint. The vibration of the motor at the no-load rated speed is analyzed using flexible multibody dynamics-electromagnetic-structural vibration coupled analysis. Comparing the vibration test results, it is confirmed that the flexible multibody dynamics-electromagnetic-structural vibration coupled analysis result predicts the actual motor vibration more accurately than the conventional finite element analysis-based electromagnetic-structural vibration coupled analysis result. By using flexible multibody dynamics-electromagnetic-structural vibration coupled analysis in the operating speed range, it is confirmed that not only electromagnetic force harmonics but also sideband harmonics caused by rotor eccentricity-induced large vibrations, and also confirmed that it accurately predicts the vibration characteristics of actual motors with rotating rotors.

Low vibration design of a variable leakage flux PM motor considering multiple operating conditions

In order to realize the low vibration design, variable leakage flux permanent magnet (VLF-PM) motor is investigated and purposefully optimized. Firstly, the variable flux characteristics of the VLF-PM motor are studied in detail. Then the electromagnetic vibration characteristics of the VLF-PM motor under different operating conditions are analyzed. On this basis, key electromagnetic force harmonics caused by the vibration at typical operating conditions and torque performances are selected to be optimized. By the adoption of multi-objective optimization, low radial electromagnetic force (REF) and high output torque can be achieved. Both simulation and experimental results verify the effectiveness of the reduced vibration design of LCF-PM motors, which provides a potential research path for the low vibration design of PM motors, especially multi-mode PM motors.

Study on the Effect of Suspension Windings on the Electromagnetic Vibration and Noise of Ultra‐high‐Speed Bearingless Permanent Magnet Synchronous Motor for Air Compressor

The electromagnetic vibration and noise level of ultra‐high‐speed bearingless permanent magnet synchronous motor (UBPMSM) for air compressors used in the fuel‐cell vehicle (FCV) is an important evaluation. A 10 kW, 100 k r/min UBPMSM is adopted as the object of study in this research. The expression of radial electromagnetic force of UBPMSM is derived through theoretical analysis, and the order and frequency characteristics of radial electromagnetic force harmonics are summarized. Through the two‐dimensional (2D) Fourier decomposition of radial electromagnetic force by finite element analysis (FEA), the main sources of radial electromagnetic force causing the electromagnetic vibration and noise are studied. The correctness of the mathematical model is verified by FEA. In addition, the three‐dimensional (3D) finite element model of the motor is established to calculate the radial modal, natural frequency, and electromagnetic vibration and noise of UBPMSM. The research shows that the spatial order of radial electromagnetic force of UBPMSM is kN and kN ± 1 (N = GCD [2p, Z], k = 1, 2, 3, …), and the noise change of UBPMSM caused by the addition of suspension windings could be ignored compared with ordinary motor. It provides reference values for the design and optimization of UBPMSM. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Harmonic and Vibration Analysis of Dual Three-Phase PMSM with One-Phase Open Circuit Fault

This paper analyzes the harmonics and vibration under different fault-tolerant current control when one-phase winding of dual three-phase permanent magnet synchronous motor (PMSM) is an open circuit fault. Firstly, the dual three-phase load condition subdomain model of breadloaf surface-mounted permanent magnet (PM) PMSM is established. Secondly, the working conditions of an open circuit fault of one-phase winding are set from the perspectives of no fault-tolerant (NFT) control, maximum torque (MT) control, minimum copper loss (MCL) control and single three-phase mode (STPM) control. The torque harmonics and electromagnetic force harmonics of the four working conditions are analyzed. Then, considering the multi-physical field of electromagnetic and structural coupling, the electromagnetic force in the motor air gap acts on the stator core, and the vibration under four different working conditions is calculated and analyzed. Through the comparison between the analytical method and finite element method, the accuracy of the established model is verified. The calculation method is effective and accurate, it can quickly predict the motor performance in case of one-phase open circuit fault of dual three-phase PMSM.

Vibration and Noise Analysis of Flux-Modulation Double Stator Electrical-Excitation Synchronous Machine

This paper studies the vibration and noise analysis of flux-modulation double-stator electrical-excitation synchronous machine (FM-DSEESM) in both no-load mode and on-load mode by using the mode superposition method. First, the theoretical excitations of vibration and noise, namely the radial electromagnetic force harmonics, are deduced and classified by their sources. Second, the finite element analyses (FEA) of these radial electromagnetic force harmonics are analyzed via Fourier decomposition and compared to their theoretical results for validation. Third, to perform the vibration and noise analysis, the modal test is conducted, and the modal FEA model is established based on the tested modal results. Also, the radial electromagnetic forces are coupled with the modal FEA model to conduct the vibration and noise analysis, and the responses of sound power levels in A-weighting are calculated. By using the modal participating factors, the main contributing modes are determined in the vibration and noise responses.

Comparative Study on Vibration Behaviors of Permanent Magnet Assisted Synchronous Reluctance Machines With Different Rotor Topologies

The rotor topologies have a great influence on the vibration characteristics of permanent magnet assisted synchronous reluctance machines (PM-SynRMs). In this article, the vibrations of PM-SynRMs with different rotor topologies are studied and compared. First, the electromagnetic force harmonics of PM-SynRMs have been studied and the design rule about the combination of stator slots and “rotor virtual slots” is given to achieve low vibration. Then, a multiphysics model is established to calculate the vibration of the PM-SynRMs with different rotor topologies. The modal analysis is conducted through finite element method considering the orthotropic of materials and validated by the modal test. Besides, the prototype has been built and the vibration test is performed to confirm the accuracy of the vibration simulation. Based on the multiphysics model, the influence of the shapes of flux barriers and the number of “rotor virtual slots” is investigated. It proves that the design rule about the combination of stator slots and “rotor virtual slots” can achieve low vibration for PM-SynRMs.

Analysis on EMF characteristics for torque ripple reduction in BLAC motor intended for HVLS fan application

This paper analyzes the harmonic characteristics of electromagnetic force (EMF) in Brushless Alternating Current (BLAC) motor for High Volume Low Speed (HVLS) fan application. Vibration and noise are one of the main crucial things in HVLS fan application. It comes from torque ripples which can be detected by harmonics of Electro Magnetic Force (EMF). Commonly, there are a few methods to eliminate the noise and vibrations issue, but most literatures only focus on small motor and not intended for HVLS fan application. Thus, the objective of this paper is to eliminate the harmonics content in EMF at early stage design. Through EMF harmonics the expected torque produced could be used to select proper slot-pole number in order to eliminate the noise and vibrations issue. In here, the analysis involves three different slot-pole numbers which are 18s/20p, 12s/10p and 9s/8p BLAC model, respectively. All models have similar volume of permanent magnet. The analysis is carried out using FLUX 2D Finite Element Analysis (FEA) for EMF computational and transient torque computation. Later, Fast Fourier Transform (FFT) analysis is used to calculate the harmonics of EMF. The analysis stage includes the EMF parameter analysis, harmonics and torque ripples analysis. It was found that 18s/20p has higher output torque with the lowest 5% torque ripple value. As a conclusion, this paper presents low torque ripple in point of view of the EMF characteristics in designing HVLS fan.

Performance Comparisons of Fractional Slot Surface-Mounted Permanent Magnet Machines With Slot-Harmonic-Only Windings

Fractional-slot slot harmonic only windings (SHOW), featured by multi-layer and varied coil turn ratios, contain only the torque-generating component and its slot harmonics in stator magnetomotive force (MMF), which makes them attractive. This paper establishes general design principles of SHOW considering different slot/pole combinations and makes detailed comparisons between SHOW and double layer (DL) windings for surface-mounted permanent magnet (SPM) machines. Firstly, fractional slot windings are classified into several categories. Similarity in distribution factors of MMF harmonics is illustrated, based on which, harmonics elimination principle of SHOW is explained. Then, general equations for calculating optimal coil turn ratios for SHOW are derived. Practical ratios approximating the optimal ones are also presented and evaluated. Furthermore, in order to show the superiorities of SHOW, 12-slot/10-pole (12s10p) and 24S10P SPM machines with SHOW are comprehensively studied and compared with their DL counterparts in terms of torque ripple, overload capability, rotor magnet loss, stator iron loss and radial electromagnetic force harmonics. Finally, 12S10P and 24S10P prototypes with SHOW are fabricated and tested for verifications.

Vibroacoustic Characterization of a Permanent Magnet Synchronous Motor Powertrain for Electric Vehicles

The vibroacoustic characterization of an electric powertrain which consists of a permanent magnet synchronous motor and a gearbox for electric vehicles is analyzed in this paper. First, the vibroacoustic origins of the electric powertrain are investigated. The influence of current harmonics on electromagnetic force harmonics is presented. The spatial distribution of electromagnetic force exerting on stator inner surfaces is investigated by a two-dimensional magnetic transient solver. The spectrum of gear meshing force is then presented. After that, the vibration response of the electric powertrain system is predicted by a mode superposition method, based on which the acoustic noise of the electric powertrain is obtained using a direct boundary element method. Furthermore, the influence of electromagnetic force harmonics and gearbox on the vibroacoustic behavior of the electric powertrain is analyzed. To verify the calculating results, a vibroacoustic test is conducted in a semi-anechoic room and the results show that both electromagnetic forces and gear meshing forces contribute to a considerable proportion of the vibroacoustic behavior due to the integrated structure.

Hybrid excitation synchronous machine finite simulation model based on experimental measurements

This paper presents a finite simulation model of the hybrid excitation synchronous machine taking into consideration the saturation effect, the iron losses and including higher-order electromagnetic force harmonics. Simulation and experimental testing prove that the advanced model represents more accurately the machine especially when compared with the basic Park model built with sinusoidal waveform assumption. The main contribution of the work is that only few experimental measurements are needed in order to implement the advanced model.

112 三次元電磁場解析による電磁力高調波を用いたモータの振動解析(音響・構造の連成解析)

Vibration and noise need to be calculated with a high degree of accuracy to estimate the radiated noise and vibration induced by the electromagnetic force from a motor. With a motor that has a three-dimensional electromagnetic field, the amplitudes and phases of electromagnetic force harmonics change with the axial position of the motor. We developed a way to analyze frequency responses of electromagnetically induced vibration using the electromagnetic force harmonics in representative plural axial cross-sections. We measured and calculated a sample motor's vibration induced by the 12th time order electromagnetic force harmonics, which has a dominant effect on the overall vibration, and we compared the vibration velocity levels. We calculated both the rotation speeds and vibration velocity levels with a high degree of accuracy at two observable peaks.

Frequency Response Analysis of Electromagnetically Induced Vibration of Inverter Motors

Vibration and noise need to be calculated with a high degree of accuracy to estimate the radiated noise and vibration induced by the electromagnetic force from a motor. In the case of inverter motors, changes in rotation speed and load lead to changes in exciting frequencies and amplitudes of electromagnetic force harmonics. We developed a way to analyze frequency responses of electromagnetically induced vibration using the electromagnetic force in a representative revolution speed in the above conditions. We measured and calculated a sample motor's vibration induced by electromagnetic force of time order harmonics, which has a dominant effect on the overall vibration, and we compared levels of vibration velocity. We calculated both rotation speeds and vibration velocity levels, which had three observable peaks with a high degree of accuracy.

Reduction of electromagnetic force harmonics in asynchronous traction motor by adapting the rotor slot number

The harmonics in electromagnetic force are a source of mechanical vibration and audible noise in an asynchronous traction motor. This paper describes an approach to reduce the force harmonics by changing the rotor slot number. Both the radial and tangential forces acting on the stator teeth are calculated by Maxwell stress tensor and their time harmonics are examined by the discrete Fourier decomposition. As a result, the optimal slot number of the rotor to reduce or eliminate the specific force harmonics is determined.

Determination of synchronous motor vibrations due to electromagnetic force harmonics

A method for the computation of magnetically induced stator vibrations in synchronous motors is presented. The electromagnetic field in the motor is calculated, and the fluctuations of the magnetic forces applied to the teeth of the stator are evaluated. The harmonics of these magnetic forces are calculated by means of a mechanical finite-element analysis, leading to determination of the motor vibrations. The method is used to compare vibrations produced by two permanent-magnet synchronous motors of different magnetic structures, one with radially oriented magnets and one with tangentially oriented magnets. The results clarify the mechanism of generation of the vibrations. >