Post-Demagnetization Performance Assessment for Interior Permanent Magnet AC Machines

This paper assesses the post-demagnetization performance of interior permanent magnet (IPM) ac machines by employing the more accurate recoil line approach based on a 2-D transient finite-element analysis (FEA). The method predicts continuous demagnetization of each magnet element undergoing partial demagnetization and evaluates the machine behavior after an event of short-circuit faults across its terminals. Along with the short-circuit faults, a failure in a drive controller or a position sensor, which may lead to a reverse voltage across the machine terminals that can eventually be more fatal and can cause significant reduction in the performance due to high levels of demagnetization, is analyzed as the worst case scenario. The FE predicted post-demagnetization performance is validated by experimental measurements in which a six-phase IPM machine designed for electric vehicle traction is allowed to lose its synchronization with the inverter when forced to operate on a torque-speed envelope, which is way beyond the drive voltage setting

Six-Phase Fractional-Slot-per-Pole-per-Phase Permanent-Magnet Machines With Low Space Harmonics for Electric Vehicle Application

This paper discusses the development of new winding configuration for six-phase permanent-magnet (PM) machines with 18 slots and 8 poles, which eliminates and/or reduces undesirable space harmonics in the stator magnetomotive force. The proposed configuration improves power/torque density and efficiency with a reduction in eddy-current losses in the rotor permanent magnets and copper losses in end windings. To improve drive train availability for applications in electric vehicles (EVs), this paper proposes the design of a six-phase PM machine as two independent three-phase windings. A number of possible phase shifts between two sets of three-phase windings due to their slot-pole combination and winding configuration are investigated, and the optimum phase shift is selected by analyzing the harmonic distributions and their effect on machine performance, including the rotor eddy-current losses. The machine design is optimized for a given set of specifications for EVs, under electrical, thermal and volumetric constraints, and demonstrated by the experimental measurements on a prototype machine

A Nine-Phase 18-Slot 14-Pole Interior Permanent Magnet Machine with Low Space Harmonics for Electric Vehicle Applications

© 1986-2012 IEEE.One of the key challenges of utilizing concentrated winding in interior permanent magnet machines (IPMs) is the high rotor eddy current losses in both magnets and rotor iron due to the presence of a large number of lower and higher order space harmonics in the stator magnetomotive force (MMF). These MMF harmonics also result in other undesirable effects, such as localized core saturation, acoustic noise, and vibrations. This paper proposes a nine-phase 18-slot 14-pole IPM machine using the multiple three-phase winding sets to reduce MMF harmonics. All the subharmonics and some of the higher order harmonics are cancelled out, while the advantages of the concentrate windings are retained. The proposed machine exhibits a high efficiency over wide torque and speed ranges. A 10-kW machine prototype is built and tested in generator mode for the experimental validation. The experimental results indicate the effectiveness of the MMF harmonics cancellation in the proposed machine

The influence of constitutive material models on accumulated plastic strain in finite element weld analyses

Recent studies in computational weld mechanics have revealed the importance of the material plasticity model when predicting weld residual stresses. The present work seeks to extend this level of understanding to include the effects of the assumed material annealing behaviour, particularly when modelling multi-pass welds that comprise several thermo-mechanical loading cycles. A series of numerical analyses are performed to examine the variability in predicted residual stress profiles for different material models, using a validated finite element model for a three-pass slot weld in AISI 316LN austenitic steel. The material models consider both the work hardening and annealing assumptions for the chosen material. Model sensitivity is established not only from a weld residual stress perspective, but also from an assessment of the post-weld plastic strain accumulated in the weldment. Predictions are compared with indirect measurements acquired using cross-weld micro-hardness maps taken from benchmark specimens. Sensitivity studies reveal that the choice of annealing behaviour will have a significant impact on plastic flow predictions, which is dependent on the annealing temperature specified. Annealing assumptions will have a varying impact on the weld residual stress predictions, such that the extent of sensitivity is dependent on the plasticity model chosen. In contrast, the choice of plasticity model will have a significant effect on the predicted weld residual stresses, but relatively little effect on predictions of equivalent plastic strain

Enhanced Availability of Drivetrain Through Novel Multiphase Permanent-Magnet Machine Drive

This paper deals with a novel multiphase permanent-magnet (PM) machine drive to enhance drivetrain availability in electric traction applications. It describes the development of new winding configurations for six-phase PM brushless machines with 18 slots and eight poles, which eliminate and/or reduce undesirable space harmonics in the stator magnetomotive force. In addition to improved power/torque density and efficiency with a reduction in eddy current loss in rotor PMs and copper loss in end-windings, the developed winding configuration also enhances availability of drivetrain, in a variety of applications requiring a degree of fault tolerance, by employing it as two independent three-phase windings in a six-phase interior-PM machine, which is designed and optimized for a given set of specifications for an electric vehicle, under thermal, electrical, and volumetric constraints. This paper also describes the design and development of a six-phase inverter with independent control for both sets of three-phase windings. The designs of the motor and the inverter are validated by a series of preliminary tests on the prototype machine drive

Continuous demagnetization assessment for triple redundant 9-phase fault-tolerant permanent magnet machine

In this study, the risk of partial irreversible demagnetisation of a triple redundant, nine-phase fault tolerant machine based on permanent-magnet-assisted synchronous reluctance machine topology has been comprehensively assessed under various faults, including the worst case scenario when the applied voltage vector is in the opposite direction of the back electromotive force due to sensing and inverter control failure, by employing a continuous demagnetisation model. The dynamic response during fault transients and the post-demagnetisation performance, such as the demagnetisation distribution, reduction in the back EMF and torque, will also be analysed and compared

The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm−1. TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described

Measurement of Leading Proton and Neutron Production in Deep Inelastic Scattering at HERA

Deep--inelastic scattering events with a leading baryon have been detected by the H1 experiment at HERA using a forward proton spectrometer and a forward neutron calorimeter. Semi--inclusive cross sections have been measured in the kinematic region 2 <= Q^2 <= 50 GeV^2, 6.10^-5 <= x <= 6.10^-3 and baryon p_T <= MeV, for events with a final state proton with energy 580 <= E' <= 740 GeV, or a neutron with energy E' >= 160 GeV. The measurements are used to test production models and factorization hypotheses. A Regge model of leading baryon production which consists of pion, pomeron and secondary reggeon exchanges gives an acceptable description of both semi-inclusive cross sections in the region 0.7 <= E'/E_p <= 0.9, where E_p is the proton beam energy. The leading neutron data are used to estimate for the first time the structure function of the pion at small Bjorken--x.Comment: 30 pages, 9 figures, 2 tables, submitted to Eur. Phys.

Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

The $B^0$-$\bar B^0$ oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives $\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)}$ ps$^{-1}$.Comment: 7 pages, 1 figure, submitted to Physical Review Letter

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results