Pole Permanent Magnet Research Articles

Optimal rotor poles and structure for design of consequent pole permanent magnet flux switching machine

Permanent magnet flux switching machines (PMFSM) have attracted significant research interest and are considered as competent candidates when higher torque density is primary requirement. However, conventional PMFSMs uses excessive rare earth PM volumes which ultimately increases machine the machine weight and PM cost. Moreover, the PMs extended at the stator yoke results in stator leakage flux which degrades the performance. To suppress the leakage flux and diminish the PM volume, the consequent pole PMFSM (CPPMFSM) with flux bridges and barriers encompassing partitioned circumferential and radial magnetized PMs is proposed, thereby ensuring an alternate magnetic path for the working harmonics which improves the modulation effect and flux distribution. Moreover, the influence of the rotor pole number on seven different rotor structures namely, curved rotor, trapezoidal rotor, wide rotor tooth tip, wide rotor base width, rectangular segmented and eccentric rotors are investigated based on the electromagnetic performance and stress distribution. Finite element analysis (FEA) reveals that the 12S-13P CPPMFSM with a wider rotor base offers comparatively better electromagnetic performance. Compare to the conventional PMFSM, the proposed CPPMFSM reduces the PM volume which minimizes the overall machine cost and weight, suppresses the torque ripples by 16.49%, diminishes total harmonic distortion (THD) by 35.24% and decreases cogging torque by 32.88%. Furthermore, the torque and power density are enhanced by 7.028% and 7.025% respectively.

Reduction of Saturation and Unipolar Leakage Flux in Consequent-Pole PMV Machine

This article proposes some effective approaches to address the inherent issues of consequent-pole (CP) permanent magnet (PM) machines, such as saturation of the salient rotor core and unipolar PM leakage flux of the end region caused by asymmetric field. The effect of CP-Halbach PM array with different magnetization directions and parameters that affect the saturation has been investigated for the CP PM machine with short pole pitch. By employing the CP-Halbach array, the saturation issue can be solved and superior performance can be obtained without reducing the PM pole arc. In addition, unequal and multistep staggered rotors with magnetic barriers have been proposed to reduce the unipolar leakage flux in the end region. Compared with regular staggered rotors, not only better electromagnetic performance can be achieved, but also the end unipolar leakage flux can be reduced. Finally, a prototype is manufactured and the predictions have been validated by measurements.

Torque sensitivity analysis for triple‐speed coaxial magnetic gear using finite element method

The authors introduce a new type of triple-speed coaxial magnetic gear (TSCMG) and analyses its operation with sensitivity analysis. The effect of various factors is evaluated on TSCMG performance, including the yoke thickness, permanent magnet (PM) thickness, number of pole pairs (gear ratios), axial length, pole-arc coefficient, PMs and air gap length. At first, a preliminary design of TSCMG is made, and then its optimal parameters are selected using sensitivity analysis based on the finite element method (FEM). Then, TSCMG is simulated by applying both preliminary and optimal design parameters. The flux density distribution and rotor torque within TSCMG are extracted. Analysis results show that TSCMG can offer higher pull-out torque and lower maximum flux density at the edges and corners of TSCMG. Finally, the performance of the designed TSCMG is validated with a prototype.

In-situ post-assembly magnetization of large rare-earth permanent-magnet machines

Auxiliary permanent magnet generator (PMG) represents an essential part of the large steam generator excitation system. It provides energy for main exciter (rated power 1600 kVA) which supplies excitation for steam generator (rated power 300 MW). While auxiliary PMG is out of service, its permanent magnets are demagnetized. In order to put auxiliary PMG into operation, magnetization of permanent magnet poles is needed. This paper presents a method for in-situ post-assembly magnetization (PAM) of rare-earth PMG by applying DC current to all three phases of its stator windings. Magnetization process is performed in the power plant, and all equipment used in experiment is readily accessible to plant maintenance personnel (transformer, rectifier, circuit breaker, cables, etc.). The main advantage of this technique is that magnetization is performed without demounting the PMG off the main rotor shaft, and as a result, generator overhaul duration is significantly reduced, and magnetization costs are decreased. Throughout the procedure, magnetizing currents, voltage on PMG stator terminals and magnetic induction (flux density) are measured. Prior to magnetization, DC currents, current pulse duration and rotor position are calculated. Based on the calculated values, the temperature rise in stator windings has to be checked. The technique is validated through case study in the real power plant at the PMG, rated power 35 kVA, which was successfully magnetized. Subsequently, the simulation is performed, in order to determine the unknown parameters of the equipment used.

Effect of number of permanent magnetic poles on 3D printed coreless generator rotor

3D-printed coreless generator using rotors with 4 poles permanent magnet and 8 poles permanent magnet as source of external magnetic field has been presented for energy harvesting applications. The prototype of proposed coreless generator is built using 3D-printer with Black Polylactic Acid (PLA) as a filament for stator housing, rotor and other parts. The major parts of the proposed coreless generator are the stator, which has four coils of winding copper wire and two rotors with four permanent magnet and eight permanent magnets which are arranging N and S magnet poles alternately. The prototype permanent magnet generator is tested with rotational speed and load condition. The experimental results have been shown that the coreless generator can generate It was found that 3D-printed coreless generator can generate electric energy up to 10300 mW for rotor with eight permanent magnets and 9000 mW for rotor with four permanent magnet at 5000 rpm, respectively.

DETERMINATION OF THE REPULSIVE FORCE OF A THICK HIGH-COERCIVE PERMANENT MAGNETS IN THE AXIAL BEARING OF A VERTICAL PUMP

The article considers the possibility of applying a standard method for calculating the repulsive force for a thick high-coercive permanent magnets from samarium-cobalt alloy in a magnetic system. The results of the research allowed us to introduce correction coefficients in the method of calculating the repulsive force in a magnetic system with such magnets, depending on the air gap between of them. It is shown that the repulsive forces of the North poles of permanent magnets differ from the repulsive forces of the South poles. The research was carried out with magnets manufactured by different enterprises. When calculating the repulsive force, the average value of the repulsive force between the North and South poles of magnets is found.

Partitioned Stator Hybrid Excited Machine With DC-Biased Sinusoidal Current

This article proposes a new partitioned stator hybrid excited (PS-HE) machine with dc-biased sinusoidal current. On the inner stator, the consequent pole permanent magnets (PMs) are employed as the PM excitation. On the outer stator, a set of integrated dual three-phase winding is adopted to produce the wound and armature fields at the same time by injecting the sinusoidal current with dc bias. So, the flexible flux regulation can be realized by controlling the dc bias component. The rotor composed of segmented iron cores is sandwiched between two stators. By employing the air-gap field modulation theory, the air-gap magnetic field harmonics are analyzed to explain the operating and flux regulation principle. Furthermore, a design optimization and the electromagnetic performances of the proposed machine are investigated by finite element analysis. When compared with the existing series and parallel PS-HE machines, the proposed machine can avoid the disadvantage of low torque density of PARALLEL HE machine, and it can solve the problem of the poor flux regulation ability of series HE machine as well, which is mainly contributed by the reasonable space allocation of PMs and field winding excitations. Finally, a prototype is built and tested to verify the theoretical analyses.

Design and Analysis of T-Shaped Consequent Pole Dual PM Vernier Machines With Differential Magnetic Network Method

This article has proposed a novel design of dual permanent magnet (PM) vernier machine (DPVM) with T-shaped consequent pole (TCP) rotor. The analytical model of T-shaped magnet rotor based on differential magnetic network method is first derived. Given the additional optimizing parameter, edge arc difference, TCP rotor has the potential to produce 6% higher fundamental airgap flux density or 30% higher PM utilization ratio than regular fan-shaped consequent pole (FCP) rotor. The influence of magnet size parameters including magnet thickness, pole pitch ratio, and arc difference angle on airgap flux density of TCP rotor is then analyzed. The torque performance of TCP in regular consequent pole and dual PM consequent pole vernier machines are also studied. The comparison shows that TCP can produce higher torque than fan-shaped magnet in vernier machines. At last, a prototype of DPVM with TCP rotor is built and tested, which has achieved 28-N·m/L measured torque density.

Optimal Design of Double-Pole Magnetization BLDC Motor and Comparison with Single-Pole Magnetization BLDC Motor in Terms of Electromagnetic Performance

This study presents an optimal double-pole magnetization brushless DC (BLDC) motor design, compared to a single-pole magnetization BLDC motor in terms of electromagnetic performance. Initially, a double-pole model is selected based on the permanent magnet (PM) of the single-pole model. The pole separation space, which is generated in the magnetization process of the double-pole PM, is selected based on the pole space of the single-pole model. Moreover, the PM offset is selected considering the PM volume of the single-pole model. Further, an optimal model is selected using the multiple response optimal method, which is a type of response surface methodology (RSM). The objective of the optimal design is to maintain the back EMF and decrease the cogging torque; the design variables include the pole separation space and PM offset. The experimental points of the initial model are designed using the central composite method (CCD). Finally, the optimization is verified by comparing the experimental and analysis results of the single-pole model with the analysis results of the optimal model.

Design and Analysis of Permanent Magnet Parameters for Interior Permanent Magnet Synchronous Motor

For improving the performance of a 3 phase 6 pole 48 slot 55kW interior “—” permanent magnet synchronous motor, the permanent magnet parameters are optimized by using finite element simulation software with the variables of permanent magnet embedding depth, permanent magnet thickness and pole arc coefficient. In order to reduce the torque of the motor slot and increase the no-load counter electromotive force within the allowable range, the permanent magnet parameters are optimized. The results show that the motor has the best performance when the depth of permanent magnet is 251mm, the thickness of permanent magnet is 19mm and the polar arc coefficient is 0.8mm.This research result has certain reference value in practical application.

Design and Performance Analysis of a Novel Outer-Rotor Consequent Pole Permanent Magnet Machine With H-Type Modular Stator

In this paper a novel outer-rotor consequent pole permanent magnet machine (OR-CPPMM) with H-type modular stator core is proposed for higher average torque ( $T_{avg}$ ), flux linkage ( $\Phi$ ) and efficiency ( $\eta$ ) whereas low cogging torque ( $T_{cog}$ ), torque ripple ( $T_{rip}$ ) and harmonics content in flux linkage ( $\Phi _{THD}$ ) and back-EMF ( ${\mathrm {EMF}}_{THD}$ ). The proposed OR-CPPMM is investigated with different stator flux gaps width for static and dynamics electromagnetic performances. Analysis reveals that flux gaps in H-type stator core not only improve electromagnetic performance i.e., $\Phi $ is enhanced by 10.23%, $\Phi _{THD}$ is suppressed by 80.65%, diminished ${\mathrm {EMF}}_{THD}$ by 59.37%, truncate $T_{rip}$ by 44.37% and improve $T_{avg}$ by 15.99% but also exhibits better flux focusing effect to enhance flux linkage and diminish harmonic contents. In addition, H-type modular stator structure provide physical isolation of adjacent phase that de-couple the adjacent phase coupling flux which enhance self-inductance and weaken mutual-inductance and hence improve fault tolerant capability. In addition, to elaborate effectiveness of the proposed design and justification of OR-CPPMM novelty with H-type modular stator, electromagnetic performance is extensively compared with existing state of the art including E-core and C-core structure. Analysis and comparison with state-of-the-art reveals that proposed OR-CPPMM enhanced $\Phi $ by 65.35%, diminish $\Phi _{THD}$ by 67.24%, truncate $T_{cog}$ by 96.72%, suppresses ${EMF}_{THD}$ by 44.40%, diminish $T_{rip}$ by 77.23% whereas $T_{avg}$ is enhanced by 91.69%. Furthermore, the proposed design novelty is justified with comparison of OR-CPPMM with inner rotor and dual rotor permanent magnet flux switching machines. Comparison and analysis unveil that OR-CPPMM exhibits $T_{avg}$ higher up to 35.16%, truncate $T_{rip}$ up to 32.88%, enhanced $\Phi $ up to 22.13% and boost $T_{den}$ to 3.41 times at the cost of 2.58% increase in $T_{rip}$ .

Influence of transverse magnetic field on the properties of laser ablation produced nickel oxide nanoparticles

Influence of transverse magnetic field on the nickel produced plasma plume and structural and optical properties of nickel oxide nanoparticles produced by pulsed laser ablation (PLA) method have been investigated experimentally. Ablation container was placed between the poles of permanent magnets. Strength of external magnetic field was controlled by the distance between magnets. The direction of the magnetic field was perpendicular to the direction of laser pulse propagation. 5 samples were synthesized in the presence of magnetic fields with different strengths in distilled water. Ablation was carried out by 1064 nm wavelength beam of pulsed Nd:YAG laser of 7 ns pulse width. Effects of external magnetic field on the properties of nickel oxide nanoparticles were characterized by X-ray diffraction patterns, field emission scanning electron microscope images, transmission electron microscope microimages, UV–Vis-NIR absorption spectra, dynamic light scattering patterns, FTIR and photoluminescence spectra. Furthermore, magnetic properties of synthesized nanoparticles were studied using their hysteresis curve which were recorded by vibrating sample magnetometer. Results show that with increasing the strength of external magnetic field, the intensity of XRD peaks of synthesized nanoparticles was increased while their size was decreased. Applying the external magnetic field caused the cyclotron motion of the charged particles in the plasma plume on the surface of target which increased their energy, and decreased their agglomeration.

Wind energy conversion system under asymmetrical voltage failures: Analysis and nonlinear control

AbstractThis work presents the analysis and proposes nonlinear controls of a wind energy conversion system (WECS) to pass through symmetrical and asymmetrical voltage failures. The WECS is equipped with a nonsalient pole permanent magnet synchronous generator (PMSG) and two full converters, synchronous generator side converter (SGSC) and grid side converter (GSC), joined by a direct current (DC) link. As a consequence of the strong disturbances considered, a general strategy based on grid voltage values changes control references at SGSC and GSC. This strategy uses two flags for indicating normal grid voltages, symmetrical faults, or asymmetrical ones. Then, while control laws deal with model uncertainties and fast disturbances due to wind gusts, the strategy changes references to surpass strong, probably unbalanced, grid voltages disturbances. To assure robust properties, controllers are designed via a conjunction of Lyapunov and passivity theories. The proposed controllers and the strategy are tested under realistic wind conditions, uncertain parameters, and strong voltage disturbances.

Surface Evaluation of a Multi-Pass Flexible Magnetic Burnishing Brush for Rough and Soft Ground 60/40 Brass.

Burnishing is an advanced finishing process that produces higher-quality surfaces with better hardness and roughness than conventional finishing processes. Herein, a flexible magnetic burnishing brush comprising stainless steel pins under permanent magnet poles was used to investigate the influence of multiple passes and directions on the produced surface of soft and rough ground prepared brass. In total, five different samples were burnished on each of the two brass samples prepared. Four samples were processed in the same direction for up to four passes and the fifth sample was processed with two passes in the opposite direction. Results indicate that there was approximately a 30% increase in hardness and an 83% increase in microroughness for rougher-surface brass samples. For smoothly prepared surfaces, there was approximately a 14% increase in hardness and a 35% increase in microroughness. In the same direction of multi-pass burnishing, increasing the number of passes negatively affected surface roughness; for rougher surfaces, the surface hardness reduced and process uniformity increased owing to surface over-hardening and flaking mechanisms, and for smoother surfaces, the hardness, roughness, and process non-uniformity increased with the number of passes owing to repeated surface deformation at some locations and high flaking at other locations. Compared to single-pass burnishing, wherein the surface roughness and microhardness showed almost no change with high process uniformity, in burnishing with two opposite-direction passes, the produced surface exhibited better surface roughness, process uniformity, and microhardness improvements owing to a reverse strain mechanism. Hence, opposite burnishing passes are recommended.

Development of Brushless Claw Pole Electrical Excitation and Combined Permanent Magnet Hybrid Excitation Generator for Vehicles

Aiming at the problems of large excitation loss and low power generation efficiency of silicon rectifier generators and the unstable output voltage of permanent magnet (PM) generators, a hybrid excitation generator (HEG) with suspended brushless claw pole electrical excitation rotor (EER) and combined magnetic pole PM rotor is proposed in the present work. With only one fractional slot winding stator, the generator adopts PM field as the main magnetic field and electrical excitation field as the auxiliary magnetic field, which not only retains the advantages of high efficiency of PM generators but also effectively reduces excitation consumption. The main structure parameters and the design method were analyzed, and a simulation analysis of no-load magnetic field distribution and flux regulation ability was carried out using finite element software to verify the rationality of the hybrid excitation parallel magnetic circuit design. Moreover, the no-load, load, regulation, and voltage regulation characteristics of the designed generator were tested, and the results show that the designed generator has a wide range of voltage regulation, which can ensure stable output voltage under variable speed and load conditions.

Nonlinear EMC Modeling and Analysis of Permanent-Magnet Slotted Limited-Angle Torque Motor

In this article, a high-precision equivalent magnetic circuit (EMC) model is first proposed for slotted permanent-magnet (PM) limited-angle torque motor (LATM) with nonuniform teeth, which leads to potential application in swing system substituting a lower torque density of the slotless structure. By the proposed relatively fine division method of magnetic reluctance in the stator tooth-tip segments, air-gap regions, and PM poles, the proposed EMC model can fully consider armature reaction and magnetic saturation problem. Subsequently, a multiobjective optimization method based on the EMC model is proposed to improve torque performance. Finite-element analysis is employed to validate the EMC model and optimization results. Following that, a curved nonwounded tooth shape is carried out and further optimized to decrease magnetic saturation of stator teeth and significantly improve symmetry of torque profile about stable equilibrium point, compared with the traditional straight tooth shape. Finally, the slotted LATM with curved teeth is prototyped, and its experimental results are presented and discussed. The simulation and experimental data show better accuracy of torque profile improvement.

Model-based design of variable speed non-salient pole permanent magnet synchronous generator for urban water pipeline energy harvester

This paper proposes the model-based design methodology of a 60-kW direct drive variable speed permanent magnet synchronous generator (PMSG) used in an urban water pipeline energy harvesting system. The whole study aims to design the PMSG considering different system parameters of the energy harvesting system such as the mechanical parameters, electric circuit, power electronics and the variable speed drive operation. The electric and geometric parameters of the PMSG is then designed based on different design constraints imposed by the system. To incorporate the effect of the variable speed drive into the PMSG electric parameters, this work introduces a parameter called κ, which can map the electric parameter variations with the variation of the PMSG input speed profile. This proposed work achieved a successful coupling among the system mechanical and variable speed drive parameters with the PMSG electric and geometric parameters. The coupling is performed in a python-based environment which couples MATLAB and Altair FLUX. The results are tested and validated against the desired values of the PMSG which shows a good agreement among different results. This whole design process can be useful in achieving a model-based design that can provide a detail analysis option before prototyping and testing different components of the harvester system.

Effect of Skewing in a Variable Flux Interior Permanent Magnet Synchronous Machine

The motivation of this article is to minimize the cogging torque and the torque ripple in a 6-pole 27-slot variable flux interior permanent magnet synchronous machine (VF IPMSM) by skewing the permanent magnets (PMs) in several steps. AlNiCo9 is used as the PM material in the rotor as the magnetization level of the AlNiCo9 PM can be changed and controlled by proper current control. The optimum skewing angles to minimize the cogging torque are found analytically and verified by using the finite-element analysis (FEA). The effect of these skewing angles on the back electromotive force and the torque ripple is also studied at different magnetization levels of the AlNiCo9 magnets. An FEA shows that a step skewed PM pole significantly minimizes the cogging torque and the torque ripple in the VF IPMSM. A current pulse in the d -axis is applied to magnetize or demagnetize each step in the step skewed PM pole. The minimum optimum skewing angle is chosen such that each step of the step skewed PM pole is magnetized or demagnetized with minimum nonuniformity.

Piecewise Stagger Poles With Continuous Skew Edge for Vibration Reduction in Surface-Mounted PM Synchronous Machines

The common method to mitigate the slot-frequency vibration and noise of the permanent magnet (PM) motors is skewing the stator slot or skewing the PM. However, the limitation of this method in pole-frequency vibration reduction exists. In this article, one method by adopting the piecewise stagger PM pole with a continuous skew edge is proposed to reduce the pole-frequency and slot-frequency vibration for surface-mounted permanent magnet (SPM) synchronous machines. First, the analysis of the radial force acting on the stator teeth is conducted. Basing on this, the limitation of the skewing slot method in reducing the vibration is revealed. In order to solve this problem, a piecewise stagger PM pole with a continuous skew edge for pole-frequency and slot- frequency vibration reduction is proposed and its principle of vibration reduction is presented in detail. The finite element models of three 6-pole/36-slot SPM motors are built to simulate the radial force. Finally, two 6-pole/36-slot SPM motors are manufactured and the experimental results validate the effectiveness of the proposed method.

SMALL-SCALE PROTOTYPE OF A FULLY HTS-2G SIX-PHASE INDUCTION ELECTRICAL MACHINE

HTS direct drive generators with high specific output mass power and specific output volume power (at the boiling point of liquid nitrogen 77 K) are needed for aviation. Elimination of the reduction unit will reduce the weight of the entire generation system. However, this puts high demands on the strength of the high-speed rotor. Other important requirements are: brushless; the possibility of adjusting the output voltage (by changing the excitation current) depending on the magnitude and type of the connected load; autonomy (no external power supply of excitation current). To satisfy all the above requirements, a fundamentally new technical solution for an electric machine was developed. The generator is a two-package hybrid of the Induction machine with combined excitation. HTS-2G windings (2x3-phases of HTS-2G armature windings and axial excitation coil) are in stationary cryostats on the stator. The rotor has alternating poles of high coercive permanent magnets and ferromagnetic poles. To ensure the alternating magnetic field of the poles of the rotor and to avoid demagnetization of permanent magnets by a counter-directed field of the axial excitation HTS coils, the rotor packages are rotated by one pole. In this case, the demagnetizing part of the axial flux is intercepted by the ferromagnetic pole of the neighboring packet.