An Improved Sideband Current Harmonic Model of Interior PMSM Drive by Considering Magnetic Saturation and Cross-Coupling Effects

The sideband current harmonics, as parasitic characteristics in permanent-magnet synchronous machine (PMSM) drives with space vector pulsewidth modulation technique, will increase the corresponding electromagnetic loss, torque ripple, vibration, and acoustic noises. Therefore, fast yet accurate evaluation of the resultant sideband current harmonic components is of particular importance during the design stage of the drive system. However, the inevitable magnetic saturation and cross-coupling effects in interior PMSM drives would have a significant impact on the current components, while the existing analytical sideband current harmonic model neglects those effects. This paper introduces a significant improvement on the analytical model by taking into account these effects with corresponding nonlinear factors. Experimental results are carried out to underpin the accuracy improvements of the predictions from the proposed model over the existing analytical one. The proposed model can offer a very detailed and insightful revelation of impacts of the magnetic saturation and cross-coupling effects on the corresponding sideband current harmonics

Stability analysis of gas solids separation in scaling-up fluidized bed reactors

In large industrial fluidized bed reactors with high gas solids flow rates, small cyclones working in parallel are often preferred to achieve higher efficiency in the case of uniform distribution of gas-solid two-phase flow across each inlet. However, there is mounting evidence1-5 that gas-solid suspensions pass through identical paths in parallel can be significantly non-uniform, resulting in a dramatically drop in overall efficiency. In this study we used the direct Liapunov method by considering the interaction between gas and solids to detect the instability of uniformity. Owing to the special symmetry in this system, the criterion can be simplified into identifying the concavity (concave or convex) of pressure drop across a single cyclone with respect to operational parameter CT. Then, based on the stability analysis of uniformity, a novel design principle is provided to prevent non-uniform distribution at high dust loading. The effect of geometrical factor, i.e. dimensionless vortex finder diameter dr, on the stability of uniformity has been further investigated. The phase diagram of stability is calculated to give a clue of designing robust parallel cyclones system. Please click Additional Files below to see the full abstract

Particle swarm optimization of air-cored axial flux permanent magnet generator for small-scale wind power systems

Axial flux permanent magnet synchronous machines with aircored configuration is particular suitable for small scale wind power system due to their advantages of low synchronous reactance, cogging torque free, high efficiency and high power factor. However, due to the number of machine parameters, with some tightly `coupled' with each other, optimisation of the design could become extremely challenging by conventional analytical means. Here, the particle swarm optimization method is used in the design of an axial flux permanent magnet generator for small-scale wind power system. Five inter-dependent design parameters are adjusted simultaneously to achieve an optimal solution for the application. Three-dimensional finite element analysis is employed to evaluate the electromagnetic performance for the optimization. The results show the proposed optimization method is efficient and with fast convergence

Putting Structure into Fluidized Bed – From Concept to Industrial Applications

Structures of particles, particle agglomerates, distributors, and internals have significantly influence on hydrodynamics and transfer behaviors of the dense gas-solid fluidized bed. For nanomaterial production, the particle surface and their agglomerated structures directly influence the fluidization behaviors; while for coal to chemical process, the distributors, internals play an important role in regime transient, and hydrodynamics. Carbon nanotubes mass production, coal to chemicals process. and fuel production were employed as examples to describe the concept of putting structures into fluidized bed, and then to put these structures into industrial applications

Design of a multi-layer interior ferrite permanent magnet synchronous machine for traction applications

A novel design of interior ferrite permanent magnet synchronous machine with multi-layer configuration is proposed for traction applications. Although the ferrite magnet can be disadvantaged by its low residual flux density and energy product, it is proposed that flux-focusing and multi-layer configurations can be utilized to harness both permanent magnet (PM) torque and reluctance torque to recoup the loss of the PM torque due to its intrinsic property. The machines with up to three-layer magnets are presented and evaluated comprehensively. The results suggest that the two-layer machine provides the best performance among the three configurations. Furthermore, compared against a commercial rare-earth equivalent, the proposed ferrite machine is shown to have nearly the same torque with 32% less electromagnetic losses. The findings underpin interior ferrite permanent magnet synchronous machine as an attractive alternative for traction application

The analytical study of stator tooth modulation on electromagnetic radial force in permanent magnet synchronous machines

The electromagnetic radial force acting on the stator inner periphery will induce radial vibration and acoustic noise in permanent magnet machines. The radial force components are transmitted through the stator teeth to the yoke to introduce deformations. The influence of the stator tooth structure can be considered as an equivalent mechanical modulation effect on these electromagnetic radial force components. As a result, high-order electromagnetic radial force components can be modulated and potentially result in eminent stator low-mode vibration. In this paper, an analytical model is developed to offer an intuitive knowledge of stator tooth modulation effect on electromagnetic radial force. The validity of the proposed analytical method has been underpinned by both finite element analysis and experimental results. Such an effective yet simple analytical model can be of significant benefit for the stator radial vibration analysis. It can be employed to not only promptly investigate the stator radial vibration characteristics but also perform effective optimization on stator radial vibration reduction in permanent magnet machine