Novel modular switched reluctance machines for performance improvement

Compared to non-modular machines, modular topologies become increasingly attractive due to their simplified manufacture process, better fault tolerant capability and potentially reduced material consumption. In order to maintain or even enhance the machine performance while achieving high fault tolerant capability, novel modular, single layer winding switched reluctance machines (SRMs) with different pole numbers are proposed, which are supplied by rectangular wave current with different conduction angles. The influences of the pole number and flux gap width between E-core segmented stators on the electromagnetic performance have been investigated in terms of self- and mutual inductances, electromagnetic torque, copper loss, iron loss, and radial force. It has been found that the modular structures with higher rotor pole numbers than stator slot numbers (12-slot/14-pole and 12-slot/16-pole SRMs) can maintain and even improve the average torque due to the nature of self- and mutual inductances. In addition, the torque ripple for modular machines are significantly reduced (below 50%), so do the iron loss and radial force, leading to higher efficiency albeit with potentially lower vibration and acoustic noise. Two prototypes with 12-slot/8-pole and 12-slot/14-pole combinations have been built with both non-modular and modular structures to validate the predictions in terms of inductances and static torques

Performance comparison of doubly salient reluctance machine topologies supplied by sinewave currents

This paper comprehensively investigates the electromagnetic performance of 3-phase, 12-slot, and 8-pole switched reluctance machines (SRMs) with different winding configurations, i.e. double/single layer, short pitched (concentrated) and fully pitched (distributed). These SRMs are supplied by sinewave currents so that a conventional 3-phase converter can be employed, leading to behavior which is akin to that of synchronous reluctance type machines. Comparisons in terms of static and dynamic performances such as d- and q-axis inductances, on-load torque, torque-speed curve, efficiency map, etc. have been carried out using two-dimensional finite element method (2-D FEM). It is demonstrated for the given size of machine considered, that for same copper loss and without heavy magnetic saturation, both single and double layer mutually coupled SRMs can produce higher on-load torque compared to conventional SRMs. Additionally, double layer mutually coupled SRM achieved the highest efficiency compared to other counterparts. When it comes to single layer SRMs, they are more suitable for middle speed applications and capable of producing higher average torque while lower torque ripple than their double layer counterparts at low phase current. Two prototype SRMs, both single layer and double layer, are built to validate the predictions

Using a novel petroselinic acid embedded cellulose acetate membrane to mimic plant partitioning and in vivo uptake of polycyclic aromatic hydrocarbons

A new type of composite membrane is introduced to mimic plant uptake of hydrophobic organic contaminants (HOCs). Petroselinic acid (cis-6-octadecenoic acid),the major component of plant lipids, was embedded in the matrix of cellulose acetate polymer to form the petroselinic acid embedded cellulose acetate membrane (PECAM). Accumulation of the polycyclic aromatic hydrocarbons (PAHs) naphthalene (Nap), phenanthrene (Phe), pyrene (Pyr), and benz(a)pyrene (Bap) by PECAM was compared with their uptake by plants. The accumulation of Nap, Phe, Pyr, and Bap by PECAM reached equilibrium in 24,48,144, and 192 h, respectively. The petroselinic acid-water partition coefficients (log K(pw), 3.37, 4.90, 5.24, and 6.28 for Nap, Phe, Pyr, and Bap, respectively) were positively correlated with the hydrophobicity of the compounds (R(2) = 0.995) and were almost the same as the lipid-normalized root partition coefficients (log K(lip)) for the corresponding compounds. Their relationship can be expressed as log K(pw) = 0.98 log K(lip). The normalized plant uptake coefficients (log K(u)) obtained by in vivo experiments with a range of plant species (2.92, 4.43, 5.06, and 6.13 on average for Nap, Phe, Pyr, and Bap, respectively) were slightly lower than those of the log K(pw) values for the corresponding compounds, presumably due to their acropetal translocation and biodegradation inside plants. This work suggests that PECAMs can well mimic plant partitioning and in vivo uptake of PAHs and may have good potential as a nonliving accumulator to mimic plant uptake of PAHs and perhaps other HOCs

Influence of Conduction Angles on Single Layer Switched Reluctance Machines

This paper investigates the influence of conduction angles on the performances of two 3-phase 12-slot/8-pole short pitched switched reluctance machines (SRMs): single layer SRM with conventional winding (SL-CSRM), and single layer SRM with mutually coupled winding (SL-MCSRM). Both unipolar and bipolar excitations are employed for the SRMs with different conduction angles such as unipolar 120° elec., unipolar 180° elec., bipolar 180° elec., bipolar 240° elec., and bipolar 360° elec. Their flux distributions, self- and mutual-flux linkages and inductances are analyzed, and followed by a performance comparison in terms of on-load torque, average torque, torque ripple, using two-dimensional finite element method (2D FEM). Copper loss, iron loss and machine efficiency have also been investigated with different phase currents and rotor speeds. The predicted results show that the conduction angle of unipolar 120° elec. is the best excitation approach for SL-CSRM at low current and also modest speed, as its double layer counterpart. However, at high current, the higher average torque is achieved by a conduction angle of unipolar 180° elec. For SL-MCSRM, bipolar 180° elec. conduction is the most appropriate excitation method to generate a higher average torque but lower torque ripple than others. The lower iron loss is achieved by unipolar excitation, and the SLCSRM with unipolar 120° elec. conduction produces the highest efficiency than others at 〖10A〗_rms. In addition, the performances of single layer machines have been compared with the established double layer SRMs with conventional and mutually-coupled windings. The prototype SRMs, for both SL-CSRM and SL-MCSRM, have been built and tested to validate the predictions

Investigation on synchronous reluctance machines with different rotor topologies and winding configurations

This paper investigates the influence of rotor topologies and winding configurations on the electromagnetic performance of 3-phase synchronous reluctance machines with different slot/pole number combinations, e.g. 12-slot/4-pole and 12-slot/8-pole. Transversally laminated synchronous reluctance rotors with both round flux barrier and angled flux barrier have been considered, as well as the doubly-salient rotor as that used in switched reluctance machines. Both concentrated and distributed winding configurations are accounted for, i.e., single layer and double layer conventional and mutually coupled windings, as well as fully-pitched winding. The machine performance in terms of d- and q-axis inductances, on-load torque, copper loss, and iron loss have been investigated using 2-D finite-element analysis. With appropriate rotor topology, 12-slot/4-pole and 12-slot/8-pole machines with fully-pitched and double layer mutually coupled windings can achieve similar torque capacity, which are higher than the machines with other winding configurations. In addition, the synchronous reluctance machine with round flux barrier can have lower iron loss than doubly salient reluctance machine under different working conditions. The prototypes of 12-slot/8-pole single layer and double layer, doubly salient synchronous reluctance machines have been built to validate the predictions in terms of inductances and torques

Comparative Study of Torque Production in Conventional and Mutually Coupled SRMs Using Frozen Permeability

This paper investigates the influence of mutual fluxes (inductances) on the resultant torque in three-phase conventional switched-reluctance machine (CSRM) and mutually coupled SRM (MCSRM) using the frozen permeability (FP) method. Under saturation conditions, the FP method allows accurately separating the torques due to self-flux and mutual flux, hence quantifying their contributions to torque generation. Then, appropriate current waveforms (unipolar or bipolar, square wave or sinewave) can be established to maximize the output torques. It is well known that the mutual torque of CSRM can be negligible. However, this paper has shown that when sinewave current is employed and under full or overload conditions, the torque will be significantly reduced due to non-negligible negative mutual torques. Different from CSRM, the self-torque and the mutual torque of MCSRM can be added if current waveform is properly chosen, e.g., sinewave currents. This can significantly boost the resultant torque. The predictions have been validated by experiments

Quantitative analysis of contribution of airgap field harmonics to torque production in 3-phase 12-slot/8-pole doubly-salient synchronous reluctance machines

This paper adopts simple analytical modelling to investigate the contribution of airgap field harmonics to the torque production in some 3-phase, 12-slot/8-pole doubly-salient synchronous reluctance machines (DSRMs) with both conventional and mutually-coupled winding configurations. The airgap flux density has been calculated based on the analytically obtained magnetomotive force and doubly-salient airgap permeance for both the double layer and single layer DSRMs with different winding configurations. Then the contribution of different airgap field harmonics to average torque and torque ripple can be investigated and validated by direct finite element analyses. It has been found that in the DSRM, the 10th order harmonic in the double layer conventional (DLC), the 4th order harmonic in the double layer mutually-coupled (DLMC), the 7th order harmonic in the single layer conventional (SLC) and the 10th order harmonic in the single layer mutually-coupled (SLMC) have the highest contribution to positive average torque while with positive influence on torque ripple reduction. However, the 2nd order harmonic in the DLC, the 8th order harmonic in the DLMC, the 5th order harmonic in the SLC and the 2nd order harmonic in the SLMC machines mainly reduce the average torque

Recent Development of Reluctance Machines with Different Winding Configurations, Excitation Methods, and Machine Structures

This paper reviews the performances of some newly developed reluctance machines with different winding configurations, excitation methods, stator and rotor structures, and slot/pole number combinations. Both the double layer conventional (DLC-), double layer mutually-coupled (DLMC), single layer conventional (SLC-), and single layer mutuallycoupled (SLMC-), as well as fully-pitched (FP) winding configurations have been considered for both rectangular wave and sinewave excitations. Different conduction angles such as unipolar120º elec., unipolar/bipolar 180 ºelec., bipolar 240 º elec. and bipolar 360ºelec. have been adopted and the most appropriate conduction angles have been obtained for the SRMs with different winding configurations. In addition, with appropriate conduction angles, the 12-slot/14-pole SRMs with modular stator structure is found to produce similar average torque, but lower torque ripple and iron loss when compared to non-modular 12-slot/8-pole SRMs. With sinewave excitation, the doubly salient synchronous reluctance machines with the DLMC winding can produce the highest average torque at high currents and achieve the highest peak efficiency as well. In order to compare with the conventional synchronous reluctance machines (SynRMs) having flux barriers inside the rotor, the appropriate rotor topologies to obtain the maximum average torque have been investigated for different winding configurations and slot/pole number combinations. Furthermore, some prototypes have been built with different winding configurations, stator structures, and slot/pole combinations to validate the predictions

Optical properties and radiative forcing of urban aerosols in Nanjing, China

AbstractContinuous measurements of atmospheric aerosols were made in Nanjing, a megacity in China, from 18 January to 18 April, 2011 (Phase 1) and from 22 April 2011 to 21 April 2012 (Phase 2). Aerosol characteristics, optical properties, and direct radiative forcing (DRF) were studied through interpretations of these measurements. We found that during Phase 1, mean PM2.5, black carbon (BC), and aerosol scattering coefficient (Bsp) in Nanjing were 76.1 ± 59.3 μg m−3, 4.1 ± 2.2 μg m−3, and 170.9 ± 105.8 M m−1, respectively. High pollution episodes occurred during Spring and Lantern Festivals when hourly PM2.5 concentrations reached 440 μg m−3, possibly due to significant discharge of fireworks. Temporal variations of PM2.5, BC, and Bsp were similar to each other. It is estimated that inorganic scattering aerosols account for about 49 ± 8.6% of total aerosols while BC only accounted for 6.6 ± 2.9%, and nitrate was larger than sulfate. In Phase 2, optical properties of aerosols show great seasonality. High relative humidity (RH) in summer (June, July, August) likely attributed to large optical depth (AOD) and small Angstrom exponent (AE) of aerosols. Due to dust storms, AE of total aerosols was the smallest in spring (March, April, May). Annual mean 550-nm AOD and 675/440-nm AE were 0.6 ± 0.3 and 1.25 ± 0.29 for total aerosols, 0.04 ± 0.02 and 1.44 ± 0.50 for absorbing aerosols, 0.48 ± 0.29 and 1.64 ± 0.29 for fine aerosols, respectively. Annual single scattering albedo of aerosols ranged from 0.90 to 0.92. Real time wavelength-dependent surface albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to assess aerosol DRFs. Both total and absorbing aerosol DRFs had significant seasonal variations in Nanjing and they were the strongest in summer. Annual mean clear sky TOA DRF (including daytime and nighttime) of total and absorbing aerosols was about −6.9 and +4.5 W m−2, respectively. Aerosol DRFs were found to be sensitive to surface albedo. Over brighter surfaces, solar radiation was more absorbed by absorbing aerosols and less scattered by scattering aerosols

Measurement of Trace I-129 Concentrations in CsI Powder and Organic Liquid Scintillator with Accelerator Mass Spectrometry

Levels of trace radiopurity in active detector materials is a subject of major concern in low-background experiments. Procedures were devised to measure trace concentrations of I-129 in the inorganic salt CsI as well as in organic liquid scintillator with Accelerator Mass Spectrometry (AMS) which leads to improvement in sensitivities by several orders of magnitude over other methods. No evidence of their existence in these materials were observed. Limits of < 6 X 10^{-13} g/g and < 2.6 X 10^{-17} g/g on the contaminations of I-129 in CsI and liquid scintillator, respectively, were derived.These are the first results in a research program whose goals are to develop techniques to measure trace radioactivity in detector materials by AMS.Comment: Proceedings of 10th International Conference on Accelerator Mass Spectrometr