PM Thickness Research Articles

Design and Analysis of Five-Phase Fault-Tolerant Vernier Permanent Magnet Machines for Direct-Drive Occasions

Abstract A fault-tolerant vernier permanent magnet machine (FTVPMM) with five phases for direct-drive occasions is designed and analyzed. The construction of the proposed FTVPMM is introduced and the principle of the vernier modulation effect is investigated. Parameters are designed and optimized by finite element analysis (FEA), including tooth width, slot opening, PM thickness, pole-arc coefficient, air-gap length, and rotor yoke. Furthermore, major electromagnetic performances are discussed, including cogging torque, no-load back electromotive force (BEMF), output torque, and fault-tolerant capability.

A High Power Factor Permanent Magnet Vernier Machine With Modular Stator and Yokeless Rotor

Permanent magnet vernier machines (PMVMs) have drawn increasingly more attention due to their high torque density. However, they suffer from low power factor due to the large harmonic inductance caused by abundant no-working harmonics. This paper proposes a high power factor PMVM endowed with modular stator and yokeless halbach-PM-array rotor. Benefited from the unique structure, the magnetic circuits of low order no-working harmonics are interrupted and their amplitudes can be effectively decreased. Meanwhile, multiple working harmonics are produced by the modulation effects of un-evenly distributed stator permeance. Thus, both the high power factor and average torque can be achieved. Moreover, the influence of critical dimension parameters, including slot bottom width, flux barrier width and PM thickness on average torque and power factor are comprehensively analyzed. Finite element analysis (FEA) and experimental results verify that at current density 10 A/mm2, the power factor and active volume torque density of proposed PMVM with 9-slot-stator 14-pole-pair PM rotor can be improved to 0.9 and 26 Nm/L, while regular PMVM counterpart is corresponding to 0.84 and 22 Nm/L, respectively.

Investigation of Air-Gap Field Modulation Effect in Spoke-Type PM Machines

In this article, the air-gap field modulation effects (AFMEs) in spoke-type permanent magnet (STPM) machines with concentrated winding are investigated and revealed by quantifying the torque contributions of the various air-gap flux density harmonics. Due to the relatively stronger flux concentrated effect, the STPM structure exhibits greater resulting air-gap field harmonics for torque generation. In order to provide an in-depth understanding of their torque generation mechanism, the contributed torque components of the various air-gap field working harmonics are quantified by employing the Maxwell stress tensor (MST) approach. It identifies a fact that the abundant air-gap flux density harmonics have participated in torque production in the STPM machine. As a consequence, the field-modulated harmonics contributed a nonnegligible torque component, and hence, a pronounced AFME can be obtained in the STPM machine. Besides, the influences of the key dimension parameters, including split ratio, stator slot opening ratio, rotor PM thickness, and length, on AFEM for torque performance of the STPM machines are evaluated by the finite-element (FE) method. Finally, the reliability and effectiveness of theoretical analysis and FE simulation are verified by experiments on an STPM machine prototype.

Design and Analysis of 15 MW SPM Vernier Generator for Direct-Drive Wind Turbine Applications

This paper presents the design and an analysis of a surface PM vernier generator (SPMVG) for MW-scale direct-drive (DD) wind turbine application. An SPMVG has the advantage of higher torque density; however, especially at higher power ratings with increased electrical loadings, the power factor worsens and there are some serious concerns including magnetic saturation of cores and PM demagnetization. These issues are directly related to machine design parameters such as PM dimensions, applied electrical loading, slot geometry and the choice of slot–pole combination. It is determined that depending on the PM thickness and a few other design variables, each slot–pole combination has an optimal value of specific electrical loading. The use of the optimal value of specific electrical loading ensures that the machine is not saturated, the performance is optimum and the power factor is not unnecessarily degraded. Moreover, under certain design constraints, design criteria are developed that ensure the proper choice of various entailed design variables. By using the developed design criteria, the trends of various electromagnetic performances with variation in the slot–pole combination are discussed. The obtained trends clearly show that each slot–pole combination offers a certain torque density and power factor; thus, it serves as a guide for the selection of the slot–pole combination considering the required torque density and/or certain power factor limit. Finally, by using the developed design approach, an SPMVG for rated power of 15 MW is designed; the design objectives are to maximize torque per volume with a power factor limit of 0.4. Moreover, the various aspects of the performances of the designed SPMVG are comprehensively compared against a conventional PM DD 15 MW generator.

Hepatocyte growth factor ameliorates methylglyoxal-induced peritoneal inflammation and fibrosis in mouse model.

Peritoneal dialysis (PD) is essential for patients with end-stage renal disease. Peritoneal fibrosis (PF) is a complex inflammatory, fibrogenic process. No effective treatments are available to prevent these processes. Hepatocyte growth factor (HGF) possesses anti-inflammatory and anti-fibrotic properties. The aim of this study was to analyze whether HGF suppresses MGO-induced peritoneal inflammation and fibrosis in a mouse model. PF was induced by intraperitoneal (IP) injections of MGO for 14days. C57/BL/6 mice were divided into three groups: Sham group (only vehicle); Sham + MGO group (PF induced by MGO); and HGF + MGO group (PF mice treated with recombinant human-HGF). PF was assessed from tissue samples by Masson's trichrome staining. Inflammation and fibrosis-associated factors were assessed by immunohistochemistry and quantitative real-time PCR. MGO-injected mice showed significant thickening of the submesothelial compact zone with PF. Treatment with HGF significantly reduced PM thickness and suppressed the expression of collagen I and III and α-SMA. Expression of profibrotic and proinflammatory cytokines (TGF-β, TNF-α, IL-1β) was reduced by HGF treatment. The number of macrophages, and M1 and M2 macrophage-related markers, such as CD86, CD206, and CD163, was reduced in HGF + MGO mice. HGF attenuates MGO-induced PF in mice. Furthermore, HGF treatment reduces myofibroblast and macrophage infiltration, and attenuates the upregulated expression of proinflammatory and profibrotic genes in peritoneal tissues. HGF might be an effective approach to prevent the development of PF in patients undergoing PD.

A comparison between conventional and flux‐intensifying interior permanent magnet synchronous machines

Flux intensifying interior permanent magnet synchronous machine (FI-IPMSM) was designed to improve the characteristic of conventional permanent magnet machines, especially, in constant power or field weakening region. Increasing a saliency ratio is the main method to achieve this target which leads to increasing reluctance torque than magnetic torque and so improving the machine performance. In this paper, the characteristics of FI-IPMSM are investigated. The effect of PM material, PM width, PM thickness, flux barriers width and iron bridge thickness on the machine parameters, output torque and no-load characteristic is studied. A comparison is carried out between the FI-IPMSM and conventional IPMSM to evaluate the improvement in machine performance. Two-dimension time-steeping finite element method (FEM) is employed in analysis of the FI-IPMSM and conventional IPMSM.

A Stator-PM Transverse Flux Permanent Magnet Linear Generator for Direct Drive Wave Energy Converter

Transverse flux permanent magnet linear generator (TF-PMLG) is widely used in direct drive wave energy converter (DD-WEC) because of its high power density. Traditional transverse flux machine (TFM) is designed and built in form of translator-PM. But translator-PM configuration needs a large amount of PM and the cost is high in long stroke application, like DD-WEC. Recently, the stator-PM linear machines have gained more attention for reducing the PM volume and improving the generator performances under low-speed conditions. In this paper, a novel stator-PM TF-PMLG for DD-WEC has been proposed. The fundamental configuration and operation principle of the generator are illustrated. Then, the expressions of the back EMF and the electromagnetic thrust are derived by magnetic circuit analysis. Main dimension parameters, such as PM thickness, central angle of the outer stator shoe and pole pitch are determined and optimized based on finite element analysis (FEA). This topology has advantages of low PM consumption and high power density, and is a suitable candidate for long stroke applications, like DD-WEC, in which a high power per PM volume is usually needed to reduce the amount of permanent magnet and ensure high power density.

An Analytical Model and Optimization of a Novel Hybrid Rotor Machine for High Torque Density

This article proposes a novel hybrid rotor permanent magnet (HRPM) machine for the performance of torque and overload capability with the constraint of the rotor diameter. In order to optimize the electromagnetic performance, an analytical model (AM) is built by the magnetic equivalent circuit (MEC) of the rotor and stator considering the saturation and leakage flux effect. A good prediction accuracy is verified by the finite element method (FEM), even in high saturation condition. Based on the AM, the characteristics of the hybrid magnetic pole rotor are analyzed by the equivalent strategy that equivalent PM remanence and thickness of single pole in rotor. Furthermore, a response surface method (RSM) for multi-variate and multi-objective optimization is adapted to improve the electromagnetic performance because of the high torque density and PM material utilization. Finally, a comparison of the torque, PM eddy current loss and anti-demagnetization performance is investigated among surface-mount PM (SPM) machine, spoke-type PM (STPM) machine and HRPM machine. The comparison results show the hybrid PM rotor machine enhances higher torque density and overload capability. Finally, a 12 slot/10 pole HRPM machine is prototyped and tested to validate the analyses.

Parameter Design for a High-Speed Permanent Magnet Machine Under Multiphysics Constraints

Regarding high-speed permanent magnet machines (HSPMMs), there is a lack of complete and detailed design processes for main parameters under multiphysics constraints, which makes it difficult to obtain high-reliability designs for designers of HSPMMs. This paper presents a detailed and complete design process for the main parameters of an HSPMM under multiphysics constraints. Firstly, the initial sizes are obtained through electromagnetic and mechanical design theory. Then, the influence of design parameters on rotor stress is analyzed in detail, including PM material, rotor temperature, sleeve thickness, PM thickness and rotor diameter. Furthermore, the rotor dynamics have also been studied in detail, including the effects of bearing stiffness, impeller mass, rotor diameter, core length, and gyroscopic effect on critical speed. Afterwards, the comprehensive research on the electromagnetic filed and the loss characteristics is performed. The cooling system is designed and the thermal field is also studied in Ansys-Cfx. Besides, the coupled temperature-stress analysis is established considering the interaction between temperature and mechanical characteristics. Finally, a full-size HSPMM prototype has been fabricated and tested to validate the detailed multiphysics design process.

Novel linear switched-flux PM machine with 9/10 primary/secondary pole number combination

Purpose – Due to linear structure, linear switched flux permanent magnet machines (LSFPMMs) also may have odd pole primary, such as 9, 15, 21, etc., without unbalanced magnetic force in equivalent rotary machines. The paper aims to discuss these issues. Design/methodology/approach – In order to increase the thrust force density, the influence of some major design parameters, including split ratio, PM thickness, primary slot width and secondary pole width, are investigated by finite element analysis. For reducing the thrust force ripple under on-load condition, the end auxiliary teeth are adopted and their positions are also optimized. Findings – This novel 9/10 primary/secondary poles LSFPMM has high average thrust force and low thrust force ripple by optimization. The results demonstrate that the odd pole primary may be a good candidate for long-stroke linear direct drive application. Originality/value – A novel 9/10 primary/secondary poles linear switched flux permanent magnet machine is developed in this paper. The similar conclusions could be obtained for other LSFPMMs with odd pole primary.

SUBPLAZMALEMMAL SRTUCTURES OF EXCITABLE AND UNEXCITABLE CELLS IN CLINICAL AND EXPERIMENTAL STUDIES

The phenomenon of PM thickness was seldom noted at investigation of cells in different organs. However just presence of such a phenomena was noted, but no valuation of its biological importance was given. In a basis of excitable and unexcitable cells plasmatic membrane thickness changes lays cell submembrane layer thickness alteration. Reversible and irreversible damages of its structures can be a key of cell dysfunction at pathology.

Dynamic Modeling and Validation of a Lorentz, Self-Bearing Motor Test Rig

A new type of self-bearing motor that uses Lorentz-type forces to generate both bearing force and motoring torque has been developed. The motor stator is of slotless construction with four three-phase windings. The motor rotor is constructed of 16 surface mounted permanent magnets (PM’s). The main advantage of the design is that it eliminates the tradeoff between motoring torque and bearing force with PM thickness as found in previous designs. This paper presents the dynamic model for the self-bearing motor and illustrates how the model is integrated into the overall system model of the motor test rig. The dynamic model is validated against experimentally measured transfer functions with good agreement between the two.

Analysis and simulation of a Lorentz-type slotless, self-bearing motor

Abstract A slotless self-bearing motor design is analyzed. The proposed design eliminates the trade-off between motoring torque and bearing force with respect to PM thickness found in many recent designs. Expressions for torque and radial force production are derived, including both control-type forces and destabilizing side-pull forces. The feedback control algorithm and simulated results are also presented. The analysis indicates that: (1) independent torque and bearing force is achieved for a large number of PM pole pairs; (2) the magnitude of both torque and bearing force increases with PM thickness; and (3) the motor is capable of stable operation as long as the winding current phase shift with respect to the PM flux is small.

Analysis and Simulation of a Lorentz-Type Slotless, Self-Bearing Motor

A slotless self-bearing motor design is analyzed. The proposed design eliminates the trade-off between motoring torque and bearing force with respect to PM thickness found in many recent designs. Expressions for torque and radial force production are derived, including both control-type forces and destabilizing side-pull forces. The feedback control algorithm and simulated results are also presented. The analysis indicates that: (1) independent torque and bearing force is achieved for a large number of PM pole pairs; (2) the magnitude of both torque and bearing force increases with PM thickness; and (3) the motor is capable of stable operation as long as the winding current phase shift with respect to the PM flux is small.