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Axial flux permanent magnet (AFPM) machines are being increasingly used in several applications owing to their outstanding features. Most importantly, they are characterized by a high power-to-weight ratio, compactness, and high efficiency. Designers of AFPM generators seek to achieve the required performance and ensure the proper operation of the machine for the targeted application. Among many other parameters, the performance of the machine is highly dependent on the air gap magnetic flux density and no-load induced voltage. Accurate computation of such parameters helps minimize the overall design process. Therefore, the estimation of flux density plays a vital role in determining many other dependent parameters in AFPM machines. This manuscript provides a robust Correlated Analytical Method (CAM) for calculating the air gap magnetic flux density and no-load induced voltage of Coreless Axial Flux Permanent Magnet Generators (CAFPMG). CAM is an extended version of the Simplified Analytical Method (SAM) that is adjusted using correlated coefficients derived from an experimentally validated Three-Dimensional (3D) Finite Element Model (FEM). A complete procedure for the calculations is provided. The results showed the integrity of the CAM compared to the results obtained from the validated FEM. Such a technique will help designers of CAFPM machines perform parametric analysis and optimization in a fast and reliable manner. [ABSTRACT FROM AUTHOR]

To research the magnetic field and mechanical characteristics of the permanent magnet governor, the static magnetic field of the sector permanent magnet is analyzed by the molecular current method in the permanent magnet governor. The magnetic flux distribution is acquired at any spatial position. Comparing the analytical value with the simulation value, the results show that they are basically consistent. Based on the analytical formula, the influence of the radial position, radial length, thickness, and pole number on the magnetic induction intensity of the permanent magnet governor is studied. Thus, it provides the theoretical reference for the structural optimized design. At the same time, a test bench was set up to measure the magnetic induction intensity. The calculation and experimental results show that the magnetic induction strength of the permanent magnet is increased by 27.5%, the axial component of the air gap flux density is increased by 14.3%, and the permanent magnet material is reduced by 7.84%. [ABSTRACT FROM AUTHOR]

To improve the performance of low-speed large-torque direct drive systems in limited space, an axial field flux-switching composite machine (AFFSCM) is proposed in this paper. The AFFSCM is composed of an axial field flux-switching permanent magnet machine (AFFSPMM) and magnetic gear. Therefore, it has the advantages of a compact structure, a large power/torque density, and a wide speed regulation range. First, the topology and magnetic modulation mechanism of the AFFSCM are investigated in detail. Then, the harmonic components of the inner/outer air-gap flux density are analyzed before and after the regulation of the rotary magnetic modulation ring. Based on this, the coupling conditions of the inner/outer air-gap magnetic field are deduced. Then the AFFSCM is initially designed, a three-dimensional finite-element model of the AFFSCM is built, and the electromagnetic performances are analyzed by the finite-element method, including the flux density of the inner/outer air-gap, the speed, the static torque, etc. Next, the cogging torque of the AFFSPMM is analyzed and optimized based on the magnetic modulation mechanism to suppress the torque ripple of the AFFSCM. Finally, an 800 W prototype is constructed and related experiments are done to validate the AFFSCM. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNT), CNT–aluminum (CNT–Al), and CNT–copper (CNT–Cu) composite wires have shown remarkable electrical and mechanical properties for developing windings of single-phase induction motor. A quest has been made that if these advanced carbon nanomaterials can outclass commonly used electrical wire metals to significantly leverage electrical machines. However, these advanced materials are still in laboratory stage and most material properties are not yet experimentally reaching to their expectations. Therefore, there is need to understand the potential of these nanomaterials for electrical machines and the numerical analysis of the performance of electrical machines with various advanced novel carbon nanomaterials is still a challenge. This paper presents a comprehensive study to compare the performance of a single induction motor with its stator and rotor made with different winding materials. In doing so, the traditional copper and aluminum rotor and stator coils have been replaced by windings made of pure CNT yarn, CNT–Al, and CNT–Cu wires. A 2-D induction machine model was developed for the simulation study conducted in COMSOL Multiphysics finite element-based software. General-purpose sizing and power equations were utilized during the computation. The simulated results of flux distribution, air-gap flux density, torque, and corresponding output power were used as criteria to determine the highest quality solution. The simulation results revealed that using CNT–Cu and CNT–Al wires as machine winding can achieve 25.9% and 16.8% higher efficiency, respectively, than using CNT wires. The motor torque from the proposed finite element model was validated against the experimental results under identical speed and input voltage, and an error of 5.9% suggests that the model can be used to predict the motor performance with reasonable accuracy. [ABSTRACT FROM AUTHOR]

In this paper, a novel mechanical flux-adjusting interior permanent magnet (MFA-IPM) motor is proposed. The key is to employ an additional mechanical flux-adjusting (MFA) device attached to one side of the rotor, which can achieve flexible adjustment of the air-gap flux and obtain a wide speed range. This system with appropriate gears uses centrifugal force to set the cylindrical PMs in a required position. The topology and working principle of the MFA-IPM motor are introduced. Then, the dynamic performance prediction between the deformation length of spring and the rotation angles of PMs is obtained by the dynamic simulation. Moreover, the electromagnetic characteristics of the proposed MFA-IPM motor and a conventional IPM motor are analysed and compared based on finite element analysis, including no-load performances, inductances, electromagnetic torque, flux-weakening ability and speed range, as well as demagnetization evaluation. Finally, a prototype MFA-IPM motor is fabricated and tested. Both the simulation and experimental results indicate the validity and feasibility of the MFA-IPM motor. [ABSTRACT FROM AUTHOR]

Vernier permanent magnet (VPM) machines have been widely used in the last two decades due to their high torque density resulting from their magnetic gearing effect. In this paper, we present a new design of VPM machine with higher efficiency and power/weight ratio than their conventional counterparts. The proposed design is a combination of discrete-pole and hybrid-pole VPM machines, which incorporates the attractive characteristics of both types to improve the distribution of air-gap flux density and reduce construction costs. The arrangement of the magnets in the stator is spoke type, and their magnetization is peripheral. In order to determine the performance characteristics of the proposed machine, an analytical model based on the subdomain method is presented. The proposed method employs a quasi-Cartesian coordinates system to express the Laplace's and Poisson's equations, as well as to determine the solution for each region. Then, the solution of the equations is written in the form of hyperbolic functions and the mathematical expression of the coefficients of the equations will be simpler. To validate the proposed analytical model, a Vernier machine is designed and fabricated and the results of the experimental experiments are compared with numerical (machine simulation in finite element analysis software) and analytical results. The comparison of these results shows that the proposed model is highly accurate. [ABSTRACT FROM AUTHOR]

In surface-mounted PM machines, the cogging torque and the low-order harmonics of the air gap magnetic flux density are the main sources of the torque pulsation. These variables are strongly influenced by the distribution of the PMs on the surface of the rotor as well as the PMs' magnetization. In the presented work, the impact of the arrangement of the PMs and the PMs' magnetization pattern is studied. The PMs are arranged by some techniques such as PM arc optimization, PM shifting, PM segmentation and applying mixed material PMs. In addition, the parallel and radial magnetizations are investigated. For this purpose, the air gap flux density and cogging torque in the slotted SPM machines are predicted analytically. Using the analytical model and applying a direct search algorithm, the optimum arrangement for each technique is found. Moreover, to perform a multi-objective optimization, a weighted normalization method is applied. Finally, the proposed model and the obtained results are validated by finite element analysis. [ABSTRACT FROM AUTHOR]

This paper presents a novel and exhaustive investigation involving in-depth analysis, performance evaluation and comparative study of two 0.75 hp, 4-pole, 1500 rpm laboratory prototypes of Brushless DC (BLDC) motors of identical nominal ratings with surface and interior permanent magnet rotor structures having the same stator and winding (integral slot distributed winding). Both the motors were designed and developed in the lab. The major electrical variables (such as rated power, speed, voltage, current, number of poles, etc.) and the stator (such as core material, stator lamination, stack length, winding pattern and wire gauge) of the fabricated prototypes have also been kept identical to pin-point the direct influence of the two different rotor configurations (viz., surface vs interior permanent magnet) on the parameters, performance and operation of these BLDC motors. Additionally, to ensure unbiased basis for appropriate comparison, the overall volumes of magnets/pole in both the motors have also been kept similar. A detailed comparison of different quantities like air-gap flux density distribution, THD in induced voltage, torque ripple, losses and efficiency, torque–speed characteristics with field-weakening capability, steady state parameters at different operating conditions, etc. has been conducted for the said motors and the salient points duly highlighted. The vulnerability of the permanent magnets to demagnetisation based on armature reaction, particularly during a sudden fault, has also been investigated in both the cases. The theoretically determined parameters and analytically evaluated performance figures have been verified through standard FEM packages, and later validated experimentally on the fabricated prototypes. Very good mutual agreement has been observed between predicted and experimental values. [ABSTRACT FROM AUTHOR]

The permanent magnet thickness (PMT) is an important parameter in the design of the permanent magnet machine, and it directly affects the air-gap magnetic field and performance of generator. In this paper, a 117-kW, 60,000-rpm, high-speed permanent magnet generator (HSPMG) is taken as an example, and a two-dimensional finite element model (FEM) is established. By comparing calculation result and test data, the accuracy of the model is verified. The air-gap flux density waveform is obtained by the FEM, and the waveform is decomposed by the Fourier transform principle. The nonlinear variation law of harmonic content with the increase in PMT is obtained, and the nonlinear variation mechanism of air-gap flux density is revealed. On this basis, the variation law of voltage and voltage regulation with the increase in PMT is given, and the PMT is optimized. In addition, the nonlinear variation law of the loss is determined. The research shows that the purpose of optimizing performance of HSPMG can be achieved by adjusting the PMT. The PMT is finally determined when the generator performance is optimal. The conclusions provide some reference for the research of HSPMG. [ABSTRACT FROM AUTHOR]