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Examines the use of permanent magnet for measuring the moisture content of wood chips, pulp and brown stock for the paper industry. Nuclear magnetic resonance measurement system; Accuracy of water measurement; Pore moisture and surface moisture.

This paper introduces an alternative pathway to designing an efficient interior permanent magnet machine (IPMM) for direct–drive (D-D) wind energy applications. It analyzes the design optimization methodology in great detail, employing multiple experimental verifications to acutely pinpoint the most desirable and feasible format. The focal objectives of minimizing cogging torque, torque ripple, and maximizing efficiency were among the priority design goals and obtained through design optimization. It is demonstrated in the process that both the torque ripple and the cogging torque can be reduced to less than 5% by adjusting the slot and pole dimensions, without any other alterations in rotor pole shaping or skewing. This paper leads the way, pioneering experimental substantiation of theory, by varying existing geometrical parameters, winding, and pole design of a basic IPMM to come up with a highly efficient wind turbine generator with negligible cogging torque and torque ripple. The electromagnetic is at the heart of this paper’s design goals, as parameter optimization is essential for a wind turbine application. The winding layout is brought under scrutiny and both the distributed and concentrated wound IPMMs are compared to further adopt the design optimization. The superiority of the concentrated-wound design is demonstrated, and consequently a prototype machine is constructed based on the proposed design for experimental verification. The results from the experiment verify the feasibility of the proposed design for D-D wind turbine applications. [ABSTRACT FROM AUTHOR]

This paper contributes to the characterisation of the brushless doubly fed induction machine (BDFIM), which is attractive as a variable speed generator in applications (off-shore wind turbine) with minimum maintenance requirements. The BDFIM has two three-phase stator windings of different pole numbers housed within the same stator slots and a short-circuited rotor winding capable of coupling fields of different pole numbers. The stator windings and rotor winding create a magnetic field distribution with a range of characteristics different to those of conventional induction machines. This paper presents an analysis to identify the field characteristics and discusses their impact on the analysis and design of the BDFIM. The characteristics are determined from an analysis of the sum of two rotating sinusoidal field waveforms and confirmed by comparison with time-stepping finite element results and measured magnetic flux density data. [ABSTRACT FROM AUTHOR]

Few of the challenges with development of a single on–board motor for direct–drive electric vehicles include high torque density and low torque ripple. Therefore, in this paper, a 36–slot, 34–pole consequent pole six–phase permanent magnet synchronous machine (PMSM) has been optimized to address the aforementioned challenges for direct–drive application. Existing literature on optimization processes that rely solely on finite element models are restricted to three–phase machines only and also take longer computation time. Therefore, this paper proposes a novel optimization approach based on supervised machine learning for six–phase PMSM. In this approach, a non–conventional extended dual dq–frame model that accounts for higher order space harmonics in inductances and flux linkages has been developed and used for accurate computation of average torque and torque ripple of six–phase PMSM. Using the performance characteristics obtained from the extended dual dq–frame model for a set of initial design candidates, support vector regression algorithm is employed for supervised machine learning and increasing solutions in the design space. Furthermore, pareto front is used for selecting optimal machine models with maximum torque density and reduced torque ripple. Multi–objective trade–offs and comparison of initial and optimized designs based on average torque, torque ripple, efficiency and cost are performed. [ABSTRACT FROM AUTHOR]

This paper employs an overhang structure for axial flux permanent magnet motor to enhance the torque density. However, the overhang structure requires a computationally expensive 3-D finite-element method (FEM) for analysis, because a quasi-3-D FEM cannot be applied to such a geometry. Thus, in order to reduce the computational cost of above-mentioned topology, this paper adopts a field reconstruction method (FRM). The conventional FRM is applicable only in the case, where the slot pitch to teeth length ratio is the same along radial direction. To address this problem, we introduce a virtual air gap concept so that it can take into account parallel slot effect as well as overhang effect. In this paper, the effectiveness of the proposed method is verified by the 3-D FEM and experimental results. [ABSTRACT FROM AUTHOR]

The analytical calculation of magnetic forces is currently an interesting alternative to the time-consuming 3-D finite-element method due to their high accuracy and low computational cost. In this paper, a new semi-analytical solution for determining the levitation force of the repulsive magnetic guidance that has a significant role for controlling and developing high precision magnetic levitation positioning system is presented. An important result is that this new expression, compared with other known equations in the literature, considers the position dependence of the magnetic levitation force over the whole travel range. In order to derive this force, the magnetic field of the permanent magnet is first calculated by introducing and solving the magnetic scalar potential. Taking Lorentz force law into consideration, the proposed equation is finally derived. This semi-analytical equation is suitable for designing and optimizing the magnetic guidance. Furthermore, it can also be used for developing other ironless actuators. The calculated levitation force from the derived equation and the verification by measurements are likewise presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper, the boundary discretization method is used to improve the traditional subdomain model. The improved model can be used to calculate the magnetic field distribution in the region containing non-orthogonal boundary, avoiding the influence of the simplified stator slot or permanent magnet shape on the results in calculating the motor magnetic field using the traditional subdomain model. In addition, the improved subdomain model can also be used to calculate the air-gap flux density when the rotor is eccentric, instead of segmenting the air-gap to an equivalent state without eccentricity. The calculation object of this paper is a surface-mount permanent magnet motor with a rectangular stator slot. The air-gap flux density under no-load and load conditions is calculated, respectively. Since the improved subdomain model does not need to simplify the stator slot shape, the magnetic potential in the stator slot is also calculated. Finally, the air-gap flux density under rotor eccentricity is calculated, and the influence of the calculating parameters on the results of the improved subdomain model is discussed. All the calculated results are compared with those obtained by the finite element method, which verifies the accuracy of the improved calculation model. [ABSTRACT FROM AUTHOR]

The development of high-temperature superconducting (HTS) electrical machines results in applications of various fields, as they have higher efficiency and power density. Numerical modeling of superconducting electrical machines is usually performed by finite element method based their electrical behavior, and H-Formulation of the Maxwell's equations is one of the models that are used tremendously due to its high flexibility and simplicity. Axial field machine (AFM) is a machine topology with higher efficiency and power density, but with more complexity when modeling. This paper proposed a new 2D model for the superconducting AFM, where the superconducting coil is simulated with a 2D infinitely long model, this model also divides the electrical machine into two parts: the superconducting parts (HTS coils, bulks, etc.) and non-superconducting parts (e.g., conventional conductors, machine structure). This paper compares the results of H-A Formulation and T-A Formulation with this approach, which requires appropriate boundary conditions and continuity between the two regions, along with correct modeling of fixed and moving parts of the electrical machine, where the geometry of this model is based on a linear synchronous machine, which means the rotor is moving linearly instead of rotation. [ABSTRACT FROM AUTHOR]

This paper proposes a model predictive current control (MPCC) method of six-phase permanent magnet synchronous hub motor (PMSHM) using auxiliary voltage vectors. First of all, 26 voltage vectors can be obtained from the switching states of six inverters, and 24 auxiliary voltage vectors can be generated by combining them. Second, four virtual voltage vectors can be found through the required locations, and the two vectors with the lowest cost will be selected by cost function. Then, additional current error correction module can better track the current. Finally, the proposed method is compared with the conventional MPCC method and another method with virtual voltage vectors. The innovation of this paper is that the recombination of vectors can better track and predict the current. A current error compensation module is added to reduce the error between the actual current and the predicted current. And the experimental results show that the proposed method has better performance such as smaller torque ripple and current THD both in steady and dynamic states. Finally, the strategy proposed in this paper was applied to the vehicle model through HIL test platform. The possibility of applying the strategy proposed in this paper to pure electric vehicles was verified under New European Driving Cycle (NEDC). [ABSTRACT FROM AUTHOR]

This paper discusses a motor that was designed to satisfy the size constraints of system by using ferrite magnet and has the same performance as rare-earth magnet motor. In general, the size of the motor is increased in order to meet the same performance of motor using a ferrite magnet, because of its very low energy density compared to the rare-earth magnet. In order to compensate for these drawbacks, spoke structures capable of generating maximum magnetic flux at the same rotor size have been frequently studied. However, the spoke type motor structure has a drawback that demagnetization occurs in a magnet-specific portion. However, because it affects harmonics of the airgap flux density by demagnetization, it affects mechanical torque ripple and vibration. Therefore, in this paper, the changed air-gap flux density due to the demagnetization phenomenon and the changed mechanical vibration are analyzed by the finite-element method. In addition, we proposed an optimal rotor structure that can reduce the demagnetization phenomenon of magnets in spoke interior permanent magnet synchronous motor. Experiments were performed to evaluate the reliability of the optimized design. [ABSTRACT FROM AUTHOR]

In an interior permanent magnet synchronous motor (IPMSM) with segmented skewed poles, the armature reaction magnetic field (AR-MF) changes nonlinearly due to the saturation of the rotor magnetic barrier. Meanwhile, this varies under different excitation currents. As a result, it is difficult to be calculated by means of analytical methods. In this paper, the calculation model of AR-MF of IPMSM is first established by vector superposition method, without considering the saturation effect of rotor and the slotting effect of stator. In the second step, the virtual magnetic field of the rotor is introduced to quantitatively calculate the influence of local inhomogeneous saturation on the AR-MF. The latter is derived by combining both the subdomain method and equivalent magnetic circuit method. The complex relative permeance is also introduced to establish the AR-MF accounting for the stator slotting effect. To validate the AR-MF calculation method proposed, an 8-pole 48-slot IPMSM with segmented skewed poles is considered as a case study, showing a comparison by both with finite element (FE) results and the electromagnetic torque measured on a test bench. The model proposed in this paper shows high accuracy and fast computation with respect to FE analysis. [ABSTRACT FROM AUTHOR]

Conventionally, for a tubular permanent magnet synchronous linear motor (TPMSLM), adopting a modular structure can effectively reduce the detent force; however, the thrust density is sacrificed via the large proportion of the flux barrier to the total primary component volume. To overcome this disadvantage, this paper proposes a novel modular TPMSLM, in which the unit primary component adopts the large slot structure containing several coils. Focusing on this motor, research on the flux linkage characteristic is performed to obtain the design principle, and then the detent force is analyzed and suppressed by reasonable design of end teeth. First, the flux linkage characteristics of the unit motor and the whole motor are investigated. Variation rule of the coil flux linkage affected by the end tooth is discussed, and the principle of realizing three-phase balance for the whole motor flux linkage is elaborated. Moreover, the principle of the detent force suppression is verified and the detent force is further suppressed through the end tooth design. Finally, a prototype is developed. The back electromotive force and the detent force were tested, which verified the effectiveness of the novel modular TPMSLM proposed. [ABSTRACT FROM AUTHOR]

This paper proposes a novel modular relieving-dc-saturation Vernier reluctance machine for electric vehicle application, which integrates the merits of a robust structure, controllable excitation field, strong fault-tolerant capacity, and enhanced torque density, benefiting from its special relieving-dc-saturation design. In the proposed machine, zero-sequence current establishes a modular magnetic path and functions as the dominant excitation source for the torque generation. Especially, slot permanent magnets are introduced into each module, which mitigates the saturation effect in stator core caused by dc-biased flux with the zero-sequence current source. Therefore, the proposed machine can achieve enhanced torque density with relatively high current density. In this paper, the machine structure and operation principle are illustrated in detail, with its electromagnetic performance evaluated by time-stepping finite-element analysis. It is revealed that, due to its relieving-dc-saturation ability, torque density of the proposed machine is enhanced by about 20% with high current density. [ABSTRACT FROM AUTHOR]

This paper proposes a flux-intensifying permanent magnet-assisted synchronous reluctance motor (FI-PMa-SynRM) using surface-inset permanent magnet (PM) instead of embedded PM in the rotor. The proposed FI-PMa-SynRM employs a small amount of PM that is inset on the rotor surface facing $d$ -axis instead of facing $q$ -axis as in common PMa-SynRMs. It also differs from conventional flux-intensifying interior PM motor, where the PM is embedded inside the rotor. The proposed motor enables making use of the arrangements of two types of flux barriers (FBs): the cutoff FB and the magnet FB, collectively referred to the outer FBs, to enhance the torque output and reduce the torque ripple. The first objective in this paper is to explain the principles of the proposed FI-PMa-SynRM, and the second is to analyze the proposed technique for enhancement of the torque output with small PM volume while keeping the lowest possible torque ripple. The finite-element analysis is employed to validate the proposed motor and analyses, and the results demonstrate their advantages and effectiveness. [ABSTRACT FROM AUTHOR]

This paper proposes a new cableless transportation system that associates a magnetic actuator with the piping system in which it travels. To achieve high-speed transport within the pipe, the proposed actuator must show excellent movement characteristics. An aluminum pipe was cut in half longitudinally, and an alternating current was passed through the cut piping. The proposed cableless actuator powered by an electric current supplied by an electric brush was demonstrated to be capable of high-speed movement in a curved pipe. A scheme of attaching a cargo container to a nodal point of the actuator using a flexible rod was also proposed. The experimental results show that the actuator can be driven through the pipe even when the curved pipe is nearly U-shaped. Furthermore, the cableless actuator transporting a cargo mass of 30 g can be driven at a speed of 87.9 cm/s in a curved aluminum pipe with a curvature angle of 22.5°. The method established in this paper is considered to be applicable to the high-speed transport of lightweight reagents, bacteria, and microfluidic chips. [ABSTRACT FROM AUTHOR]

In this paper, the design of the concentrated flux-type synchronous motor (CFSM) using ferrite permanent magnets to improve torque is proposed for an automotive chassis actuator. The thin pancake type CFSM of this paper has considerable axial magnetic leakage flux due to structural reasons. It is, therefore, necessary to improve the torque. In order to meet the required specifications in a constrained installation space, this paper proposes two methods for torque improvement. The first method is the alternate-stacking core as this structure removes the magnetic leakage flux path. The second method is the rotor overhang that increases the air-gap flux density. Furthermore, the structures require a three-dimensional (3-D) finite element method (FEM) analysis for accuracy. However, to analyze the characteristics easily and quickly, the 3-D structure is made into the equivalent 2-D FEM through an analytical method using an equivalent magnetic circuit. Finally, in this paper, the validity of the design process and the effectiveness for torque improvement is verified through experiments. [ABSTRACT FROM AUTHOR]

This paper proposes a new Vernier reluctance machine (VRM) drive for electric vehicle. The key is to incorporate both stator-slot permanent magnets (PMs) and zero-sequence current as the excitation source to establish a parallel magnetic field and interact with armature winding. In this way, two different machines, namely, slot-PM-excited VRM and dc-excited doubly salient machine, are artificially integrated into a single structure, which contributes to enhance the torque density. Moreover, flexible flux control can be realized by regulating zero-sequence current. In this paper, the machine structure and operation principle are introduced, with its feasibility verified by both finite-element analysis and prototype experiments. [ABSTRACT FROM AUTHOR]

Iron nanopowders (Fe-NPs) were extracted and downsized by evaporating the iron powders in an atmospheric microwave plasma flame. The microwave plasma, which was generated by a mixture of nitrogen and argon swirl gases, evaporated the iron powders, immediately downsizing them to Fe-NPs. Subsequently, the Fe-NPs samples were collected by using bar magnets inside the collecting chamber. The Fe-NPs were analyzed by X-ray diffraction, Raman spectroscopy, optical emission spectroscopy, and a scanning electron microscopy. The Fe-NPs consisted of only iron phase and no Fe2O3 or Fe3O4 phases were formed during synthesis. The average sizes of the raw iron powders and the Fe-NPs were approximately $20~\mu \text{m}$ and 20 nm, respectively. The proposed method is simple and easily scalable. Thus, it is suitable for the mass production of Fe-NPs, overcoming the limitations of other catalyst-based synthesis methods. This paper provides a potential method for large-scale production of metal nanopowders which have potential applications in various fields owing to their unique properties at the nanoscale. [ABSTRACT FROM AUTHOR]

Tubular-switched reluctance linear launcher (TSRLL) with novel structure is proposed in this paper. The structure of switched reluctance motor is simplified, and the unbalanced force of common types of switched reluctance linear launcher is alleviated in TSRLL. The structure of the single-phase TSRLL with transverse flux is introduced thoroughly. The 3-D finite-element (FE) model of the proposed TSRLL is constructed, and electromagnetic analysis is performed by the FE method (FEM). To improve the electromagnetic force of the proposed launcher, the sensitivity analysis is conducted by means of 3-D FEM. The stator yoke thickness, mover cylinder’s thickness, stator pole arc, and pole width ratio of TSRLL are optimized, and the results of the sensitivity analyses are presented. TSRLL with two different polarity distribution patterns is compared via static FE analysis. The dynamic simulation of TSRLL with optimal specification and polarity distribution is carried out and demonstrated, of which the results agree well with the static analysis by FEM. [ABSTRACT FROM AUTHOR]

This paper proposes some practical methodology and design aids for the linear motion servocontrol systems such as the electromagnetic launchers. Mason’s gain formula was first used in the state space to solve for the transfer function of the complex and multiloop system rapidly and conveniently. The classical feedback control referring to the separation principle, involving a tracking controller and an observer-based compensator, may work well but has limited bandwidth under the constraint of the nominal inertia, and this fact is demonstrated rigorously in this paper and improved by a novel compensation scheme. According to the time-domain performance and Nyquist view, a delicate parameter design of control parameters is made for the tracking controller and the robust observer. The algorithm is verified by use of a rapid control prototype real-time simulation platform. The comparison of the experimental results shows that the proposed control scheme has good properties of trajectory tracking, antidisturbance, and noise suppression. [ABSTRACT FROM AUTHOR]

Use of low static magnetic fields for nuclear magnetic resonance (NMR) signal detection remains a challenge due to low signal-to-noise ratio, low energy difference between energy levels, and less spin transitions due to limited availability of spins. Despite these challenges, different measurement techniques based on low static magnetic fields, stray magnetic fields, and non-uniform fields have been implemented. In this paper, an approach toward using low static fields generated by permanent magnets for portable magnetic resonance applications is described. Finite element simulation models of different magnet geometries are used to develop an estimate of the magnetic field distribution exterior to the magnet. A concentric ring magnet geometry is selected to obtain flexible control of localized regions of uniform magnetic field. An estimate of the NMR voltage for different magnet sizes and orientations is presented. It is expected that the findings of this paper would be valuable for design of future portable magnetic resonance systems. [ABSTRACT FROM AUTHOR]

A novel hybrid-flux permanent-magnet (PM) generator, which has both axial flux and radial flux, is proposed. An axial-flux PM generator is designed by a reluctance network method and the 3-D finite element method. Using these results, this paper proposes a radial-flux and hybrid-flux machine, whose main dimensions are chosen to the same values as a commercialized one. The proposed hybrid-flux machine has the largest output power per volume. The power density of the proposed generator is 9.4 times larger than that of the commercialized one. The efficiencies of the proposed hybrid generator and a radial generator are same as each other, and are larger than those of an axial and the commercialized generators. [ABSTRACT FROM AUTHOR]

Through numerical simulations and calibrated experiments, the aim of the work presented in this paper is placed on the development of a polarity changeable magnetizing platform for a rotary magnetic encoder using a permanent magnet and thin silicon steel plate. Parameter studies are conducted via finite-element analyses to obtain optimized geometric design parameters for the magnetizer, leading to desirable magnetic flux density and effective magnetized patterns on the magnetic media. [ABSTRACT FROM AUTHOR]

This paper presents performance improvements of a double excitation synchronous motor by using a reluctance network (RN). The distinguishing feature of the double excitation principle is to use permanent magnets with high energy, while air-gap flux is flexibly controlled by field windings. Therefore, the first contribution of this paper focuses on maximizing air-gap flux range control. Second, an approach for torque ripple reduction is proposed by directly modifying air-gap flux according to the instantaneous torque profile. The achieved resultant torque stays almost constant for a case study. The validity of the RN method is examined by comparisons with 3-D finite element and experimental results for several machines. [ABSTRACT FROM AUTHOR]

This paper proposes an analytical model for the prediction of air gap magnetic field distribution for axial flux permanent magnet (AFPM) machine with various types of misalignments. The AFPM machine geometry is first transformed to a polar representation. Consequently, the subdomain model based on current sheet technique is developed. Then the stator coordinate system is chosen as reference coordinate to consider both static/dynamic angular and axis misalignments. The back electromagnetic forces and cogging torque are obtained accordingly based on Maxwell's equations. The results show that the proposed approach agrees with the finite-element method. The model is further validated by experiments under healthy, dynamic angular and axis misalignment conditions, which can validate the proposed approach. It turns out that the proposed approach can predict the performance of AFPM machines with types of misalignment quickly and effectively, which is greatly significant for further fault detection. [ABSTRACT FROM AUTHOR]

Modularization design has been widely used to reduce the detent force of permanent magnet linear synchronous motor (PMLSM). For modular PMLSM, ideally, unit motors are independent of each other and the detent force of the whole motor is the sum of that for unit motors; thus, the whole motor's detent force can be suppressed by adjusting the phase difference among the unit motors’ detent forces. But actually, there is coupling effect between adjacent unit motors, which has adverse effect on the detent force suppression. The coupling effect changes the magnetic field distribution, which is often neglected in current research. Hence, this paper carries out the research on magnetic field analysis and flux barrier design for modular PMLSM considering the coupling effect: the influence of the coupling effect on the air gap magnetic field is clarified through magnetic field analysis; the coupling force is isolated by finite element analysis, and then the effects of key parameters are discussed; the whole motor's detent force model considering the coupling effect is established, and an optimal design method of adjusting the flux barrier length is presented to suppress the detent force. Finally, a prototype is made to test the detent force characteristics with different flux barrier lengths, which verifies the research theory in this paper. The research results in this paper can provide guidance and reference for the design of modular PMLSMs. [ABSTRACT FROM AUTHOR]

This paper presents a fault-tolerant operation for dual three-phase surface-mounted permanent magnet machines (SPMSMs) that were both electrically connected on three winding phases and mechanically connected on one shaft. The open-phase fault-tolerant operation is considered in dual three-phase SPMSMs drive thus combining motor drive of three-phase and single-phase. The proposed method controls the torque of each motor with different phases using a single inverter. In order to control these motors, the torque and current are distributed between the motors with the specific ratio. Methods for minimizing torque ripple and copper losses and maximizing the output torque of the three-phase motor are stated in this paper. Accordingly, a system with cost-effective and enhanced reliability is proposed without any configuration adjustment or auxiliary switching devices. The mathematical analysis and experiments are presented to verify the feasibility of the proposed method. After the fault, the resulting system is able to provide up to 75% of the rated torque, and up to 50% of the torque can be utilized without any torque ripple. [ABSTRACT FROM AUTHOR]

In an open-end winding permanent magnet synchronous machines drive with single dc voltage source, zero-sequence current (ZSC) can lead to a high current stress of power modules and loss of motor. Therefore, some modulation strategies have been employed to alleviate ZSC by suppressing zero-sequence voltage (ZSV). However, ZSC still exists in the system because ZSV can also be generated by other nonlinear factors of inverter such as the dead time of system. In addition, zero-sequence back electromotive force in the zero-sequence path can also enlarge torque ripple and ZSC. In order to deal with above problems, first, this paper proposes a full-order adaptive zero-sequence observer to estimate future ZSC and ZSV, which are able to compensate one-step control delay. Second, to achieve the maximum voltage dc bus utilization, this paper proposes a novel deadbeat predictive current control (DPCC) scheme with alternate sub-hexagonal center pulsewidth modulation strategy to suppress ZSC and torque ripple simultaneously. Finally, this paper presents a comparative study of two types of methods, namely traditional DPCC scheme and the proposed DPCC scheme. Simulation and experimental results are demonstrated to verify the effectiveness of the proposed DPCC scheme. [ABSTRACT FROM AUTHOR]

This paper proposes a method to reduce the torque pulsation of the three-phase fractional-slot concentrated-winding (FSCW) interior permanent magnet (IPM) motor by lowering sub-harmonics. The key principle of this method is the selection of an optimized six-layer winding with different numbers of conductors. Firstly, the interaction of stator-rotor magnetomotive force (MMF) which contributes to the torque pulsation is analyzed. Additionally, the relationship between sub-harmonics (1st sub-harmonic and 2nd sub-harmonic) and torque pulsation orders is revealed. Then, different numbers of conductors are adopted in coils to eliminate the 2nd sub-harmonic. Nevertheless, the 1st sub-harmonic increases in the two-layer and four-layer windings. Therefore, the optimized six-layer winding is employed to suppress the 1st sub-harmonic and ensure that the 2nd sub-harmonic is zero. Besides, there are almost no other harmonics except the main harmonic and slot harmonics in the proposed IPM motor. Hence, the torque pulsation can be greatly reduced even under different current angles. Furthermore, the principle for torque pulsation reduction by lowering sub-harmonics is revealed. The effectiveness of the proposed method is verified through the comparisons with finite element analysis and experimental test. [ABSTRACT FROM AUTHOR]

This paper develops an improved dual-stator Vernier machine using ferrite magnet materials, aiming to replace an industrial interior permanent magnet machine with rare earth magnets in a low speed industrial application. The improved Vernier machine design adapts the single winding dual-stator topology with an empty inner stator core mainly to improve the torque density and eliminate the heat from the inner stator windings of conventional dual-stator Vernier machines. A drum rotor is also proposed to provide mechanical and structural enhancements. This paper compares the performance of the improved Vernier machine design against an industrial interior permanent magnet machine with rare earth magnets. The comparison shows that the improved design using ferrite magnets has even higher torque density and efficiency than those exhibited in the industrial interior permanent magnet machine with rare earth magnets. The improved Vernier machine design has considerable potential to replace industrial rare earth interior permanent magnet machines in low speed applications. [ABSTRACT FROM AUTHOR]

For the short-term high torque output, an improved model predictive direct torque control (MPDTC) method with field enhancing is proposed to increase torque. In order to avoid the possible loss of synchronism while increasing torque, the MPDTC method limits the load angle in the cost function. Under the constant load angle limitation, the improved method increases the torque output capability by increasing the magnetic field. This paper starts from the torque calculation, theoretically analyzes the torque-load angle characteristics, and illustrates the flux vector trajectory with the voltage limit circle and current limit circle. The proposed method maintains the dynamic and static performance of the traditional MPDTC method while ensuring the system stability. The experimental results show that the torque capacity of the proposed method has been improved, and it has stable extreme output torque. So, some applications, such as electric load simulators, can choose the motor with small capacity and small inertia, thereby weakening negative effects of the inertia torque. [ABSTRACT FROM AUTHOR]

This paper presents a fast analytical model for estimating the components of the PM flux density distribution in the air-gap for a number of interior permanent magnet synchronous machines (IPMSMs). Deriving the two-dimensional (2-D) analytical model for IPMSMs is more challenging compared to that of surface-mounted permanent magnet synchronous machines (SPMSMs) due to the inconsistent geometry of the rotor in polar coordinates. IPMSMs are usually modeled by using 0-D or 1-D methods such as the magnetic equivalent circuit (MEC); however, the MEC method is unable to take into account the tangential component of the magnetic flux density vector. In this paper, a 2-D analytical no-load electromagnetic model for five rotor topologies of IPMSMs is proposed. The effects of the stator slots on the radial component of the PM flux density distribution in the air-gap are then included by defining an air-gap function. The effects of the stator slots on the tangential components of the PM flux density distribution in the air-gap are also considered by injecting virtual surface currents (VSCs) or virtual permanent magnets (VPMs). For verification purposes, the analytical results are compared with those of the finite element method (FEM) and the experimental results of one of the cases. [ABSTRACT FROM AUTHOR]

For the advantages of oriented silicon steel sheet (OSSS) with better magnetic permeability in the rolling direction, this paper proposes a permanent magnet (PM) torque motor with armature teeth made by OSSS. This paper introduces the influence of unequal tooth width on the winding factor and the width calculation method of the armature teeth tip top, and analyzes the torque performance improvement by OSSS. In the end, based on testing the B-H waves of OSSS, the flux linkage, back electromotive force, rated torque and overload torque of three motors with different structure or material are compared by finite element software. The results show the proposed motor can increase the torque density and overload ability. [ABSTRACT FROM AUTHOR]

This paper proposes the multi-material topology optimization for the simultaneous design of segmented permanent magnet (PM) arrays, coil, and iron materials in magnetic actuators. Specifically, the proposed approach can find the optimal layout and shape of PM, coil, and iron materials, as well as the optimal border and magnetization direction of segmented PM arrays. For designing the layout and shape of actuator components, the discrete material optimization-type material interpolation scheme is employed in this paper. To attain the design of segmented PM arrays, an orientation design variable in Cartesian coordinate is utilized with the penalization scheme for the discrete PM magnetization directions. To validate the effectiveness of the proposed actuator design approach, two numerical examples are presented. In the examples, the actuator components (i.e., segmented PM arrays, coil winding, and back iron) are designed aiming for maximizing the magnetic force magnitude acting on the actuator plunger. [ABSTRACT FROM AUTHOR]

In this paper, the air-gap flux density components in the eccentric surface-mounted phase modulation (SPM) machines are predicted analytically. In the provided model, the slotting effects of the armature are taken into account. In the modeling process, conformal transformations (CTs) are employed to obtain an equivalent concentric slotless machine for the eccentric slotted PM machine. To satisfy the condition of using CTs, i.e., having a Laplace equation, the PMs are replaced with an equivalent current sheet at the surface of the rotor. The approach of finding this current sheet is approved by the basis of the electromagnetic theory. One of the contributions of this paper is that the provided model is capable of modeling the eccentric SPM machines with any PM magnetization pattern by means of CTs. Substituting the predicted air-gap flux density components in the Maxwell stress tensor, the machine unbalanced magnetic force and its cogging torque are computed. Finally, the accuracy of the obtained results is evaluated by means of finite-element analysis. [ABSTRACT FROM PUBLISHER]

This paper presents an analysis of the direct- and quadrature-axis inductances for linear tubular actuators with permanent magnet arrays, highlighting and featuring how they are affected by the end effects. A semi-analytical and an experimental analysis are performed to prove the influence of end effects on self- and mutual inductances. The synchronous parameters, i.e., d - and q -axis inductances of the actuator, are determined using a semi-analytical method and an experimental method. Once the synchronous parameters are all identified, high performance control methods (such as direct force control and vector control) may be implemented. [ABSTRACT FROM AUTHOR]

This paper deals with equivalent 2-D finite-element (FE) models of permanent magnet lead screw (PMLS), to accurately predict the thrust force. Due to the helical-shape permanent magnets (PMs), the magnetic fields of PMLS are typically 3-D and non-symmetric. However, the PMLS is approximately symmetric in some cases and an equivalent 2-D axis-symmetric FE model is developed instead of 3-D models. The problem lies in that no evaluation about the accuracy and applicability of the 2-D axis-symmetric FE model was offered in previous literature. In this paper, the 2-D axis-symmetric FE model is derived based on the concept of equivalent current sheets of PMs. The limitations of the existing 2-D axis-symmetric FE model are clarified, and a novel equivalent 2-D torque FE model is then proposed to predict thrust force with the gear ratio when the 2-D axis-symmetric FE model is not appropriate. It is shown that the choice of equivalent 2-D FE model depends on the lead angle of PMLS, 2-D axis-symmetric FE model is applicable in the range of (0°, 15°), and 2-D torque FE model is preferred in the range of (65°, 90°). [ABSTRACT FROM AUTHOR]

For the purpose of saving energy resources, it is extremely expected to develop highly efficient electric motors. Different types of permanent magnet (PM) arrangement can significantly affect the performance of the motors. Conventionally, the arrangement of the PMs is determined by designer’s experience. This paper focuses on the optimal design of PM arrangement in PM synchronous motors (PMSMs). We present a general pattern of the PM arrangement in PMSM. By varying the parameters of the general pattern, it can produce different types of PM arrangement in the rotor. The employed approach combines the global optimization method with the finite-element method for solving the optimization of the PM structures. Based on the proposed general pattern and optimization methods, the best PM arrangement in the motor can be automatically determined. In order to reduce computing loading, this paper employs the response surface models for reducing the computing time of objective functions. In the end, numerical tests are designed to showcase the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents an engineering modeling methodology for magnetostrictive materials based on a simplified piezo-electric governing equation. For verifying the modeling performance, a proof-of-concept non-contact strain sensor utilizing a prototype magnetostrictive (Fe–Ga alloy, Galfenol) strip on a steel plate is used to evaluate sensor performance prediction. Typically, the performance of Galfenol is measured in a compressional load region because it has a higher response. However, in this paper, we are aiming to develop a sensor for tensile stress measurement. To achieve a compression effect from a tension load in the sensing element, a Galfenol strip is aligned perpendicular to a tension bar so that tension in the bar creates compression in the strip via the Poisson effect. The experimental setup in this paper consists of a polycrystalline Galfenol strip bonded in the horizontal direction of a steel dog-bone shaped tension specimen. Permanent magnets are attached at each end of the Galfenol strip to provide an even magnetic bias field through the strip. The magnetic flux through the Galfenol strip is measured with non-contact Hall sensors during the tensile load test. The simulation results agree well with the experiments for the value of $H$ studied. [ABSTRACT FROM AUTHOR]

In this paper, a changeable winding brushless DC (BLDC) motor for the expansion of the speed region is described. The changeable winding BLDC motor is driven by a large number of phase turns at low speeds and by a reduced number of turns at high speeds. For this reason, the section where the winding changes is very important. Ideally, the time at which the windings are to be converted should be same as the time at which the voltage changes. However, if this timing is not exactly synchronized, a large current is generated in the motor, and the demagnetization of the permanent magnet occurs. In addition, a large torque ripple is produced. In this paper, we describe the demagnetization of the permanent magnet in a fault situation when the windings change, and we suggest a design process to solve this problem. [ABSTRACT FROM AUTHOR]

This paper presents a new structure of Permanent Magnet Flux-Switching Linear Motor (PM-FSLM) with a simple low weight modular primary and acceptable thrust ripple production. A flexible Magnetic Equivalent Circuit (MEC) is applied for modeling the proposed machine, which is capable to analyze the performance of different structures of PM-FSLMs. The saturation and end-effect phenomena are considered by a nonlinear permeability function and virtual zones at both ends of the machine, respectively. The machine operation under dynamic load is also investigated and its specifications are obtained. The proposed PM-FSLM has more power capability, lower current un-symmetry, and simpler mover structure compared to other ones, which can be mentioned as its benefits. Finally, the results of the proposed method are validated by the Finite Element Method (FEM) to show the effectiveness of the proposed MEC technique in terms of accuracy and processing time. The introduced linear machine and the proposed analysis method with adjustable accuracy are the paper novelties, which are presented in this work for the first time. [ABSTRACT FROM AUTHOR]

In this study, an investigation of winding structures is performed for 3-phase unbalanced and asymmetric winding permanent magnet (PM) machines including different slot-pole combinations. There are two different cases for unbalanced winding (UBW) structure: 1) Stator slot number of the machine is divisible by three, 2) Stator slot number of the machine is not divisible by three. Only the first case is examined in this paper. The unbalanced winding layouts are created for minimum unbalance and maximum winding factor. Total magneto motive force (MMF) distributions for nine different slot-pole combinations and their harmonic contents are presented. Variation of the amount of unbalance for different slot-pole combinations is also provided in the paper. Key issues arising from the asymmetric and unbalanced windings such as degree of asymmetric and unbalanced magnetic pull are explored. A prototype motor with 39-slots and 12-poles has been manufactured for experimental verification. A comparison between the finite element analysis (FEA) results and experimental results is presented for the prototype motor for both no-load and on-load conditions. It is shown that the asymmetric and unbalanced winding PM motors have significant potential for applications requiring smooth torque operation. [ABSTRACT FROM AUTHOR]

Recently, dual-rotor motor (DRM) has emerged as an alternative for an induction motor (IM) or a permanent-magnet (PM) motor for electric vehicle application, due to its better drive performance and better torque density. This paper presents an analytical model for the hybrid IM-PM configuration of DRM. The analytical model can be used to predict induced bar currents, electromagnetic torque generated, and magnetic fields in various regions of the motor. The mentioned calculations are performed under steady-state conditions. The analytical method is developed using the subdomain model approach in 2-D polar coordinates. Appropriate governing equations along with boundary conditions across all the sub-domain regions of the DRM are employed to calculate the magnetic vector potential in all the regions. The developed analytical model has been validated with finite-element analysis for various operating conditions, and high accuracy has been achieved for all the results. [ABSTRACT FROM AUTHOR]

High-temperature superconducting (HTS) maglev system, based on the magnetic flux pinning characteristic of non-ideal type II superconductors, can realize self-stable above permanent magnets. HTS maglev possesses the advantages of low-energy consumption, simple mechanical structure and environment-friendly, which make it an ideal high-speed transportation mode. When an HTS maglev vehicle crosses a ramp, the levitation height will fluctuate due to the rapid change of the track curve, which may affect the safety and stability of the system. In this paper, first, a levitation force model was obtained based on experimental data. Based on this model, a dynamic model of the HTS maglev vehicle-bridge coupled system was established. The dynamic response of the maglev train was simulated and analyzed when it operated through track grade change points under different track slopes, vertical curve radii and speeds. The influence of these parameters on the stability of the system was investigated, and the optimized design parameters for the vehicle and the track slope are proposed as well. This study provides references for the future engineering development of HTS maglev transportation. [ABSTRACT FROM AUTHOR]

A hybrid analytical and lumped-parameter thermal model is proposed in this paper to estimate the transient and steady-state two- and three-dimensional (2/3-D) spatial magnet temperature distributions for an interior permanent magnet synchronous machine (IPMSM). On the basis of a lumped-parameter thermal model (LPTM), the magnet analytical thermal models (ATMs) are synergized to establish the hybrid thermal model. By utilizing the transient or steady-state boundary conditions calculated by the LPTM, the ATMs are obtained by solving the heat conduction equations to estimate the spatial magnet temperature distributions in the 2-D horizontal-vertical and axial-vertical planes, which can also be extended to the 3-D temperature distribution by utilizing the multi-slice method. Meanwhile, the non-uniform magnet eddy current loss is also considered. Finally, both electromagnetic-thermal coupled finite element analysis method and experiments are used for verification based on a totally enclosed IPMSM. [ABSTRACT FROM AUTHOR]

In this paper, an interior permanent magnet (IPM) machine is presented and optimized for heavy-duty vehicle direct-drive applications. Since efficiency decrease and serious heating come along with excessive core loss under flux weakening control, a rotor topology with the combination of the eccentricity structure and magnetic barriers is proposed. The key is to achieve the comprehensive optimization of the proposed rotor topology to satisfy the different requirements under diverse operating points. Then, a multi-objective automatic parallel optimization method is applied, which simultaneously analyzes multi-condition operation without weight coefficients defined artificially. The 3D Pareto solution set is generated by using nature inspired evolutionary algorithm based on the high-precision metal-modals of optimal prognosis, which reduce the needed computation cost significantly. Moreover, the back electromotive force total harmonic distortion, torque and core loss of the optimal machine are analyzed at corresponding operating points. Finally, the finite-element results are validated by experiments based on a prototype machine. [ABSTRACT FROM AUTHOR]

One of the main obstacles to the robust optimization for permanent magnet machines is the high computational burden, which is mainly caused by the robustness evaluation process considering the manufacturing uncertainties. In this paper, a sequential sampling Kriging model is adopted to estimate the design robustness, and the problem of high-dimensional variables for the surrogate model due to uncertainties is avoided through adopting the worst-case based approach. To further reduce the number of finite element analyses (FEA) required for constructing a metamodel, a multi-points sequential sampling process with a two-step optimization oriented surrogate model updating algorithm is proposed. Compared with the FEA directly based robust optimization in previous work, similar Pareto Fronts are achieved by adopting the meta-model proposed algorithm but the overall run time reduced by 75%. In the end, an optimization problem for a 1.2 kW motor is considered by applying the proposed algorithm, and two prototypes with deliberately designed tolerances, imitating the worst-case scenarios in the real world, are manufactured. The worst-case torque ripple is reduced from 7.6% to 4.8% after optimizing, and this verifies the efficacy of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Superconducting (SC) electrodynamic suspension (EDS) has a wide application prospect due to the advantages of no active control, self-stability and large gap, especially in the ultra-high speed maglev, rocket launching, Electromagnetic Aircraft Launching System and other high speed fields. SC coils and null-flux Ground Coils which are the primary and secondary windings respectively are applied in a typical EDS system, in that the null-flux ground coils provide levitation and guidance force. The calculation of electromagnetic forces that has been extensively studied by scholars all over the world is the basis of the design and optimization of the system. However, due to the limitation of complex structure, the calculation formula is often so complicated that the results have to be obtained by means of finite element method and numerical simulation. This paper aims to derive an analytical calculation of electromagnetic forces for SC EDS system based on some reasonable assumptions. The experimental data of MLX01 on the Japanese Yamanashi testline was used to verify the calculation model of this paper. In order to get a further validation, a small EDS rotary table was built based on null-flux ground coils and permanent magnets. The results of the experiment confirms the effectiveness of the proposed analytical calculation model. [ABSTRACT FROM AUTHOR]

Integrated battery charging (IBC)—multiplexing the motor windings as line inductors for charging electric vehicle battery packs—can improve the onboard charging capability without increasing the weight and cost. However, during the charging operation, currents flowing in the stator winding definitely generate a magnetic field, which may demagnetize the permanent magnets (PMs) in the PM traction motors. In this paper, the demagnetization effects of IBC current on magnets in interior PM machines are compressively investigated. In this paper, a recursive algorithm to update the PM magnetization states by using a parallelogram hysteresis model at different demagnetization levels is applied. The PM temperature is also considered for establishing this model. By coupling this algorithm to the finite element analysis, the demagnetization transit at different demagnetization levels can be assessed. By decomposing the flux density of each node within the magnets along its magnetization direction, irreversible demagnetization can be accurately evaluated. Impacts from both the pulsating and rotating demagnetization magnetic fields during the IBC operation are assessed and compared. [ABSTRACT FROM AUTHOR]

Reduced sensor systems are a topic receiving increasing attention as manufacturers seek to reduce costs by removing components from systems. One popular option is to remove phase current sensors and to estimate the missing currents using the ones remaining. This paper proves that it is possible to estimate the three-phase currents of an anisotropic permanent-magnet synchronous machine drive when only one-phase current sensor is present. The necessary conditions for observability and stability have been derived, providing certainty for the design of a permanent-magnet synchronous machine drive controller. The concept has been verified with high-fidelity simulations and experiments that show the one-phase current sensor observer is capable of controlling the drive system in the presence of sensor noise and significant parameter errors. The proposed phase current observer can be used to remove one sensor from a drive system by employing the two sensor observer with the one sensor observer acting as a failsafe. [ABSTRACT FROM AUTHOR]