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The fractional-slot, concentrated-winding, interior permanent magnet synchronous motor (FSCW IPMSM) has advantages, such as reducing motor copper consumption, improving flux-weakening capability, and motor fault tolerance, and has certain development potential in application fields such as electric vehicles. However, fractional-slot concentrated-winding motors often contain rich harmonic components due to their winding characteristics, leading to increased motor losses and back electromotive force harmonics, thereby affecting the efficiency and constant power speed regulation range of the motor. Based on this, this article first uses the winding function method to explore the inductance and saliency ratio of the interior permanent magnet synchronous motor with different slot pole combinations in the fractional-slot concentrated- winding of electric vehicles. Secondly, this article will establish a 2D finite element parameterized model to analyze and compare the performance of fractional-slot concentrated-winding motors with different slot pole combinations, including air gap magnetic density, back electromotive force distortion rate, overload multiple, and torque. The structural parameters of the motor were optimized with the objective of minimizing the torque ripple under the constraint of minimizing the average torque reduction. The motor slot width, permanent magnet angle, and permanent magnet pole arc angle were analyzed and optimized. The simulation results showed that 12 slots and 8 poles were the optimal design schemes, providing a theoretical basis for the selection of slot pole coordination in the fractional-slot concentrated-winding interior permanent magnet synchronous motor for electric vehicles. [ABSTRACT FROM AUTHOR]

The paper presents the results of research on the spatial distribution of the multi-phase, distributed windings in electric machines. The focus was on the analysis of the harmonics of the current linkage spatial distributions. To perform calculations for different windings patterns, taking into account the number of phases, pole pairs, and the number q of slots per pole and phase, the dedicated code was developed in the Matlab environment. Nine different multi-phase windings were studied, for which magnetomotive force (MMF) was determined to investigate the harmonic content and total harmonic distortion. The obtained results were compared with a reference three-phase symmetric system. Studies were also carried out on torque ripple and power density for different numbers of winding phases. [ABSTRACT FROM AUTHOR]

Currently, excessive AC loss in the rectangular winding motor used for electric vehicles poses a significant challenge, necessitating effective measures to suppress the losses. This paper focuses on the Prius IV motor, employing a finite element two-dimensional model established using JMAG software. The influence of conductor material and the number of rectangular winding layers on motor AC loss under various operating conditions is thoroughly analyzed. Maintaining a constant number of rectangular winding layers, aluminum (Al) conductors replace copper (Cu) conductors in 2-layer, 4-layer, 6-layer, and 8-layer configurations, respectively. AC losses are compared among motors with 4-layer, 6-layer, 8-layer, and 10-layer Cu rectangular windings, all having identical slot dimensions. Subsequently, the 10-layer Al conductor scheme is chosen to optimize motor design. The results demonstrate an average reduction in AC loss up to 59.24% after motor optimization, further reducing motor manufacturing costs. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The humidity role in the partial discharge (PD) inception mechanism is quite complex, and there is no widely accepted theory that can describe the humidity effect on PD. In this article, the PD activity of interturn insulation of electric motor winding is experimentally investigated for different relative humidity (RH) conditions at 30 °C ambient temperature. Since the inception of PD leads to a boost in the dissipation factor (i.e., tan $\delta$) and insulation capacitance (IC), tan $\delta $ and IC tip-up test can be adopted as an indirect measurement of PD. The test campaign is carried out employing twisted pairs as samples, and both tan $\delta $ and IC are measured under a sinusoidal voltage regime. Apart from being indirectly detected, PD activities are also directly measured through a photomultiplier, while the tip-up test is performed. The adoption of direct PD measurement is to discriminate the PD from other ionization processes (e.g., water film ionization), which cannot be distinguished by indirect measurement. The experimental findings allow stating that the change of PD inception voltage (PDIV) at higher RH is due to the different places of water film formation on the insulation surface, and Paschen’s law combined with finite element analysis is used to interpret the effect of water film on PDIV. In addition, it is verified that the tan $\delta $ and IC tip-up test is not suitable for indirect measurement of PD in high humidity conditions. In fact, the higher leakage current, due to the water condensation on the insulation surface, influences the tan $\delta $ and IC measurements causing an increment in their values regardless of the PD inception. [ABSTRACT FROM AUTHOR]

A very simple and therefore wide-spread way to control motor speed and torque is to regulate the stator voltage by pulsewidth modulation (PWM). Depending on the modulation type, number of inverter levels, and modulation index of the PWM, various spectral components occur in the supply signal and inject ripple current in the motor phases. This current distortion can cause significant additional losses in the stator and rotor core, permanent magnets, and windings of an electric machine. Therefore, it is important to consider these losses in an early design stage. In this work, an efficient calculation method for harmonics of multilevel PWM signals and generated phase currents with different modulation types is presented. The PWM losses are calculated via 2-D finite element method analyses. The calculation and simulation workflow is realized within the software tool SyMSpace and applied to a three-phase permanent magnetic synchronous machine (PMSM). Loss measurements at different PWM frequencies and load points are conducted on a 3-phase PMSM. Since simulation and measurement results show good accordance, the proposed methods could be validated. [ABSTRACT FROM AUTHOR]

The three‐phase permanent magnet synchronous motor (three‐phase PMSM) has gained much popularity in many applications due to its various advantages. In addition, due to the good fault tolerance, simple inverter circuit structure and high torque density, the six‐phase PMSM has better prospects than three‐phase PMSM in biomedical devices, electric vehicles and other fields with high reliability requirements. In this study, a six‐phase axial‐flux PMSM inherently without cogging torque is proposed to improve torque density, which equips the 60° phase‐belt toroidal winding (60°TW) and slotless stator core. Based on the same effective volume, permanent magnet material, power grade and the other major motor parameters, two six‐phase PMSMs with 30° phase‐belt toroidal winding (30°TW) and 60°TW are designed, respectively. The armature reaction field, air gap magnetic density, back‐electromotive force, output torque, loss characteristic and torque‐speed characteristic are compared by using three‐dimensional (3D) finite‐element models in detail. Finally, the experimental test is carried out using the prototype of three‐phase PMSM with 120° phase‐belt toroidal winding. The experimental results indirectly verify the feasibility of 60° phase‐belt toroidal winding and correctness of 3D FEM. The 3D FEM analysis results are presented to show that torque density of the proposed six‐phase PMSM with 60°TW is improved in comparison to the six‐phase PMSM with 30°TW. Index Terms—60° phase‐belt toroidal winding, axial flux, six‐phase permanent magnet synchronous motor, torque density [ABSTRACT FROM AUTHOR]

Accurate understanding of losses and frequency‐dependent winding parameters have been an important aspect for selecting the right configuration of stranded conductors in power‐electronic inductors. An approach for modelling frequency‐dependent parameters of a winding with twisted wire bundles in toroidal inductors using a multi‐axial sliced finite element (FE) modelling approach is presented here. A 2D magnetodynamic FE problem is solved in several axial and radial slices of the inductor, accounting for the twisted conductor bundles by varying the conductor positions in the slices. Case studies are presented for different levels and pitch lengths of twisting. The approach is validated against 3D FE simulations in the case of 3–4 parallel strands and against measurements in the case of 75, 105 and 125 strands, which would be impossibly heavy for conventional 3D FE tools. The results provide insight into the effect of strand grouping, twisting levels and twisting pitch on the frequency‐dependent resistance of windings. [ABSTRACT FROM AUTHOR]

This paper investigates the spin rate bounds, the configuration stability subject to the solar wind fluctuations, and sail angle control of an electric solar wind sail (E-sail) by a high-fidelity tether dynamic model. This model describes the elastic deformation of tethers with inter-connected 2-noded tensile elements discretized by the nodal position finite element method. The E-sail is assumed to be an axisymmetric system spinning in the plane normal to the heliocentric ecliptic plane. The upper and lower spin rate bounds are revisited to reveal the physics that dictates these bounds and analytic expressions are provided to ensure the proper operation of E-sail. Then, the influences of the solar wind fluctuations on the configuration stability of the E-sail are investigated by parametric analysis with different E-sail configurations, sail angles, and spin rates. Finally, an alternative sail angle control strategy for the E-sail is proposed by applying control force at the remote units with a simple PD control. Numerical analysis demonstrates that the sail angle of E-sail can be controlled quickly by the control law at the remote units with a high-precision. • Derived a new theoretical lower bound of spin rate for E-sail with auxiliary tethers. • Analyzed structural dynamics of E-sail by a high-fidelity tether dynamic model. • Revealed necessity and effectiveness of auxiliary tethers by tether dynamic perspective. • Controlled sail angle by applying control forces at remote units only. [ABSTRACT FROM AUTHOR]

In high power electrical machines, the leakage magnetic flux due to end windings induces eddy currents in clamping devices. However, it is quite difficult to quantify these losses. In order to study the effect of different clamping materials and the impact of the magnetization direction, an experimental mock-up composed of a stator and a clamping plate has been developed. An axial coil generates a circumferential magnetic flux in the stator core at different frequencies. Eddy current losses in the clamping plates are deduced from a power balance by subtracting Joule losses and iron losses from the total measured losses. Iron losses are deduced from 3D FE calculations while the impact of the frequency on B(H) curve is taken into account. Losses in the clamping device are then analyzed depending on experimental parameters. [ABSTRACT FROM AUTHOR]

Wound-Rotor (WR) resolvers are the most commercially used resolvers in industrial applications. In this regard, the present study evaluates the effect of different winding arrangements on the accuracy of WR resolvers. To this end, three windings were proposed for the stator of the resolver containing on-tooth overlapping winding, distributed lap winding, and distributed concentric winding. Those windings were also applied to the rotor. All the rotor windings were assumed to be single- and two-phased. In addition, the effect of damper winding was also evaluated in this study. The analysis was done using time-stepping finite element method, and the most accurate resolver was built and tested. Close agreement between the results from experimental measurements and finite element confirms the obtained results. [ABSTRACT FROM AUTHOR]

Today, many applications requiring mass manufacturing are shifting to robotic applications through automation systems. The actuators used in these robotic systems should be designed according to needs. In this study, an air core spherical motor which has rotor and stator winding arrangement is described. The spherical motor's windings are optimally positioned on the stator made of delrin. Mutual inductance and self-inductance change were examined according to r=4, 20, 40 and 60 mm radius and the change in the number of stator winding for the spherical motor. Changes in inductance were found through curve fitting method with the coefficients of cubic equations. Equivalent circuit with winding inductance model is also given. Torque change according to magnet change was also investigated. Magnetic flux density change of N52 M magnet 3 winding 2-pole model was examined and the effect of the increase in overall size on torque was evaluated. [ABSTRACT FROM AUTHOR]

The propulsive characteristics of an Electric Solar Wind Sail are usually evaluated using a simplified model in which all the sail tethers are coplanar and form a sort of rigid disk. However, the three-dimensional arrangement of the tethers is fundamental information in the study of the spacecraft performance, and must be accounted for in refined mission analyses. In this paper, a Finite Element approach is chosen to estimate the deflected shape of the tethers, thus allowing important information on the structural response of the sail to be obtained. A parametric code is developed to perform a static analysis of an Electric Solar Wind Sail, whose requirements are given in terms of payload mass and spacecraft characteristic acceleration. In particular, the tether structural response is investigated using three different beam models, which are compared in terms of accuracy and computational efficiency. The analysis is specialized to the noteworthy case of a Sun-facing sail that is placed at a distance of one astronomical unit from the Sun. The numerical results, which concern a set of possible sail configurations, are compared with those taken from analytical models. • The paper analyzes the E-sail deformed shape using a finite element approach. • A parametric procedure is proposed to perform the E-sail static analysis. • The tether structural response is investigated using three different beam models. • The numerical results are compared with those taken from analytical models. [ABSTRACT FROM AUTHOR]

This article presents a permanent magnet planar translational generator which is able to exploit multiple modes of sea wave energy extraction. Linear electrical generators have recently been studied for the exploitation of sea wave energy, but, to the best of our knowledge, no synchronous planar translational generator has been proposed. In this article, to maximize the energy extraction, we have considered all the potential modes of motion due to wave excitation and included them within the mathematical model of the proposed system. The principle of operation of the generator can be summarized as follows: the moving part (translator) of the generator is driven from the sea waves and induces and electromotive force (EMF) on the windings mounted to the armature. The movement of the translator is 2-D and, therefore, all the movement modes of the wave, except heave, can be exploited. The proposed mathematical model includes the dynamic equations of the translator and the electric equations of the windings. The coupling parameters (inductances and fluxes) have been determined by finite element method analysis. Optimization of the device has been performed by considering both, the parameters of the electromagnetic circuit, and, the parameters associated with the stochastic features of the wave. [ABSTRACT FROM AUTHOR]

An induction machine with combined star-delta stator winding is analysed by means of numerical simulations based on lump parameter and finite element method (FEM) models. The use of combined star-delta winding may lead to suppressing selected higher spatial harmonics of the magnetic flux density in the air gap and, thus, to lowering the energy losses and improving the energy efficiency of the machine. [ABSTRACT FROM AUTHOR]

Complex harmonic analysis (CHA) provides a computationally efficient alternative to finite element analysis (FEA) for modelling multi-phase wound field synchronous machines. This paper presents three methods that could improve the accuracy of the CHA: by improving the equivalent air gap, by including a saturation factor, and by using image methods for computing end-winding inductance. The comparison against a finite element method and experiment shows the improved complex harmonic method could predict waveforms reliably, where a dynamic finite element method would be time-consuming. This paper shows the method is valid for a five-phase generator. [ABSTRACT FROM AUTHOR]

This study presents a comparative study of different modular brushless wound rotor synchronous machines (MB-WRSM) using non-overlapping fractional slot double-layer concentrated windings. The goal of the study is to highlight the structure which offers the best fault-tolerance capability and the highest output performance. The fundamental winding factor is calculated by using the method based on voltage phasors as a significant criterion to select the preferred numbers of phases, stator slots, and poles. With the limited number of poles for a small machine (3.67 kW/7000 rpm), 15 different machines for different phase/slot/pole combinations are analysed using two- dimensional (2D) finite element method and compared according to three criteria: torque density, torque ripple, and machine efficiency. The seven-phase/seven-slot/six-pole machine is chosen with the best compromise of high torque density, small torque ripple (3.89%), and high nominal efficiency (95%). This machine is then compared with a reference design surface-mounted permanent magnet synchronous machine (SM-PMSM). The simulation results are discussed and demonstrate that the MB-WRSM presents interesting performance features, such as extended field weakening range, with overall performance closely matching that of an equivalent SM-PMSM. [ABSTRACT FROM AUTHOR]

Here, the selection of optimal slot/pole (Ns-slot/pr-pole) number combination between the pairs of fractional slot concentrated winding (FSCW) permanent magnet synchronous machines (PMSMs) with Ns = 2pr ± 1 or Ns = 2pr ± 2 will be analysed by a modified winding function accounting for slot opening and validated by finite element method. The results show that for FSCW PMSMs with Ns = 2pr ± 1 or Ns = 2pr ± 2, the higher pole machine will have larger winding factor and hence better torque performance than the lower pole one. Moreover, it also reveals that this torque advantage is more evident in the external rotor machine than that in internal rotor machine. [ABSTRACT FROM AUTHOR]

This study investigates the field-weakening capability of interior permanent magnet (IPM) and surface-mounted permanent magnet (SPM) machines with distributed windings by considering phase voltage distortion in field-weakening region. For analysis and comparison, the Nissan Leaf vehicle traction machine is studied as a reference benchmark machine and then a comparable SPM machine is designed within the main constraints of the benchmark machine. A finite element analysis model of the benchmark machine is developed and validated by published experimental measurement. Sinusoidal phase current is desired to enhance machine torque performance and power electronic converters employing vector control method are commonly used for traction machine supply. However, the machine terminal phase voltage distortion may introduce additional difficulties for machine control. Therefore, firstly, phase voltage distortions of IPM and SPM machines with distributed windings are compared and the mechanisms are discussed. Due to the voltage distortion, the peak value of phase voltage may be higher than the fundamental one. Therefore, the influences of IPM and SPM topologies on machine traction characteristics are investigated. The study indicates that SPM machines with distributed windings can be designed to achieve comparable torque and power performance and better field-weakening capability compared to IPM machines. [ABSTRACT FROM AUTHOR]

This paper presents a linear variable reluctance permanent magnet (LVRPM) machine where the armature winding and inset Halbach array permanent magnets (PMs) are mounted on E-core stators. The Halbach array consists of a vertically magnetised PM pole and a salient ferromagnetic iron pole (split tooth) sandwiched between two horizontal PMs. The translator consists solely of laminations with salient iron poles. As a variable reluctance machine, it exhibits inherent magnetic gearing and a higher force and power density than the conventional synchronous PM machines. Finite element analysis (FEA) has been used to investigate the effect of machine parameters. The logical development of the LVRPM from the more conventional Vernier Hybrid machine is presented, including a near 50% reduction in magnetic flux leakage and a higher flux per unit magnet mass. [ABSTRACT FROM AUTHOR]

In an electrical machine design, thermal management plays a key role in improving the performance and reducing size. End-windings are commonly identified as the machine hot-spot. Hence, lowering and predicting end-windings temperature are crucial tasks in thermal management of electrical machines. This paper proposes and investigates a noninvasive but effective cooling method that aims for a uniform cooling of a machine's winding by implementing direct cooling on its end-windings. Modeling and experimental results show that a 25% hot-spot temperature reduction on a particular application can be achieved. To analyze the proposed technique in detail, an accurate but computationally economic lumped parameter thermal network is developed. Comparison between a “standard” thermal network and its simplified equivalent (with less nodes) is presented where the models are developed and fine-tuned based on experimental data. All the above is used to investigate the potential of the proposed end-winding cooling method with different configurations of the methodology. [ABSTRACT FROM AUTHOR]

This paper studies the dynamic characteristics of an electric solar wind sail (E-sail). A high-fidelity multiphysics model is developed by the nodal position finite element method to investigate the coupling effects of orbital and self-spinning motions of the E-sail, and the interaction between the axial/transverse elastic motions of tether and the Coulomb force. Furthermore, parametric study is conducted to better understand these coupling effects. The simulation results show that the coupling effects have a significant impact on the dynamic behavior of E-sail and the induced thrust. Furthermore, the analysis indicates a strong dependence of the thrust on sail and coning angles of E-sail even in the case of small sail angle. Finally, the influence of the initial self-spin rate and the sail angle on the dynamic behavior of a flexible E-sail is investigated. It shows that a high spin rate is needed to hold the geometrical configuration of the E-sail, and the difference in the orbital maneuvering is distinct when the E-sail inclines to the incident solar wind. It implies that a suitable control strategy should be employed to accomplish the thrust vectoring for the orbit maneuvering. The analysis provides an effective and robust way to design the E-sail in the mission planning phase. • Developed high-fidelity multiphysics model for electric solar wind sail. • Revealed coupling effect of orbital and self-spin motion of E-sail. • Studied interaction between axial/transverse motion of tether and Coulomb force. • Studied influence of initial self-spin rate & sail angle on flexible E-sail dynamics. • High spin rate is needed to hold the geometrical configuration of E-sail. [ABSTRACT FROM AUTHOR]

Overvoltages and dielectric stresses caused by transient conditions can result in the failure of transformer windings. Adequate prediction of these conditions is generally based on the implementation of accurate computer models, which, in turn, require an accurate computation of electrical parameters. This paper analyzes the computation of frequency-dependent core and proximity losses included in the transient model of transformer windings, using the finite element method and analytical expressions. A modified formula to calculate the proximity losses is presented. The results from a frequency-domain winding model are compared with experimental measurements on a disk-type prototype winding. These results show that including the frequency-dependent proximity losses is essential to accurately reproducing the experimental results. They also show that the core losses have a modest effect on the transient response of the winding when compared with measurements. [ABSTRACT FROM AUTHOR]

This study proposes a comprehensive model to investigate winding vibration characteristics. The radial vibration model is firstly established based on the Euler-Bernoulli beam theory, and the radial acceleration is found to be the second derivative of deflection under the quasi-static load. The fluid-loading effect of oil on winding vibration is then investigated through experimental modal analysis and finite element method. This effect leads to the decrease of natural frequencies and the increase of damping ratios. The harmonic response of axial winding vibration at 100 Hz shows the symmetry distribution that vibration on the one quarter and three-quarters of the winding height are larger than other positions. The radial acceleration is not affected by the clamping pressure, whereas the axial acceleration is in a reciprocal relationship with it. [ABSTRACT FROM AUTHOR]

This paper presents the comparative study of coreless-type permanent magnet linear synchronous machines with non-overlapping windings. An analytical expression that can be applied to any combinations of pole and coil numbers is developed for evaluating the electromagnetic performances. Subsequently, a simple factor called thrust factor is introduced to find the best ${\boldsymbol{C}_{\boldsymbol{pp}}}$ family depending on the variation of coil width ratio. From the comparative study, a significant result is reported that ${\boldsymbol{C}_{\boldsymbol{pp}}} = 1/4$ , i.e., multiple 4-pole/3-coil, is the best non-overlapping winding configuration of coreless-type permanent magnet machines owing to the highest value of thrust factor. Finally, the validity of the key analyses is confirmed by optimal results, finite element results, and experimental results from prototype machines. [ABSTRACT FROM AUTHOR]

In switching power supplies, the transformer leakage inductance (TLI) is of considerable practical significance. Ordered winding is the certain assumption in previously reported works for the calculation of the TLI value. However, disordered windings are usually unavoidable in practice and their effect on the value of the TLI is considerable. The problem becomes more complex when the number of winding turns increases. In this paper, the effect of winding disorder on the TLI value is investigated. In disordered wrapping, the winding turns arrangement (WTA) of each produced transformer is different from the others. Thus, each produced transformer has an exclusive TLI value in a disordered wrapping. Moreover, the number of possible WTAs is high, especially in transformers with a large number of winding turns. The proposed method utilizes an analytical tool for estimating the distribution of the TLI values for all of the possible WTAs. This estimation is carried out based on the limited number of the WTAs. The required number of WTAs is calculated and the validity of the proposed method is checked with Kolmogorov–Smirnov theorem. The TLI value is calculated by means of the stored magnetic energy in different parts of the transformer using the magnetomotive force variation method. Finite element simulation and experimental results are presented to show the effects of disorder on the TLI value and the validity of the proposed analytical method. [ABSTRACT FROM AUTHOR]

This paper models a huge family of electrical machines featuring simple salient poles in a unified way based on the general airgap field modulation theory. The modulation principle is analyzed by introducing the magnetomotive force (MMF) modulation operator, which characterizes the influence of a variable reluctance block on the primitive magnetizing MMF distribution established by field winding. Popular machine topologies are investigated in detail from the perspective of an airgap field modulation mechanism. The iron core magnetic potential drop due to the finite slot opening depth and the impact of iron saturation on the parameters are considered by proper theoretical indication. In addition, the modulation effect of salient poles highly depends on the slot-opening-width-to-pole-pitch ratioϵ. The effect can be neglected whenϵ< 0.3 and the best modulation results will be achieved whenϵ= 0.5. It is also found that mainly three different harmonics parts modulated by salient poles contribute to airgap flux density and torque production. Straightforward relations between the frequency-domain or amplitude information of performances indexes and topological parameters can be obtained obviously by certain analytical expressions without heavy finite-element analysis (FEA). Analytical results are verified by two-dimensional FEA and experiments measurements. [ABSTRACT FROM AUTHOR]

For large oil-filled transformers, the oil flow and temperature distribution in transformer windings are an essential issue to be addressed. However, the computation of the oil flow and temperature distribution is a complicated engineering problem because of the complex physical structure of the winding area and the coupled effect of electromagnetic, fluid and thermal fields. This study presents a multi-filed coupled approach to compute and analyse the oil flow and temperature distribution of the winding area for an ODFS-334 MVA/500 kV single-phase auto-transformer. The eddy current losses of the transformer winding discs are computed based on the combined finite element and analytical method, and the computational fluid dynamics based on 3D fluid-thermal coupled method is used to calculate the oil flow and temperature properties of the prototype. The computation of the oil flow and temperature distribution reveals accurately the hot spot of the transformer. To validate the feasibility and applicability of the proposed method, the numerical results obtained using the proposed method are compared with those of the experimental ones. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central China Normal University is the property of Huazhong Normal University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Permanent magnet (PM) motors adopt interior V-type PMs and fractional-slot concentrated winding for improving the torque density and efficiency. However, the no-load magnetic coefficient will be increased, which would reduce the utilization rate of the PM. The structure parameters of the rotor should be designed reasonably, especially the bridge. This paper calculates the no-load leakage coefficient by establishing the analytical model of the no-load magnetic coefficient. It shows that, the bridge size has an important effect on the no-load magnetic coefficient. The analysis results are verified by the two-dimensional finite element analysis and tests. [ABSTRACT FROM AUTHOR]

In this paper, the open-circuit dc-winding-induced voltage in a wound field switched flux (WFSFs) machines is analyzed. The phenomenon of open-circuit dc-winding-induced voltage is illustrated and the mechanism is explained. Rotor skewing is proposed to reduce the open-circuit dc-winding-induced voltage, and the optimal skewing angle is analytically derived based on the analytically deduced harmonic orders of the open-circuit dc-winding-induced voltage. Finite-element (FE) analyses show that the open-circuit dc-winding-induced voltages in the analyzed 12-stator-pole partitioned stator WFSF machines having 10-, 11-, 13-, and 14-rotor-pole rotors can be effectively reduced by >94%, while the ac-winding phase-fundamental back-EMFs can be maintained by >95%. Twelve/ten-stator/rotor-pole prototypes with skewed and nonskewed rotors are built and tested to verify the analytical and FE results. [ABSTRACT FROM AUTHOR]

This paper investigates a novel three-phase doubly salient permanent magnet (DSPM) motor. Because of the adoption of Π-shaped stator iron core segments, the asymmetrical magnetic circuit among different phases occurring in conventional DSPM motors with E-shaped stator iron core segments can be avoided, so that balanced and sinusoidal three-phase PM flux linkage and no-load electromotive force (EMF) can be achieved. First, based on a 12/7 stator/rotor pole combination, the operation principle of Π-core DSPM motor is discussed using the least magnetic reluctance principle. Then, the general airgap field modulation theory is extended to the Π-core DSPM motor for explaining its operation principle further and armature winding connection. The finite element analysis is used to validate theoretical analysis, as well as to calculate its electromagnetic performances. The results show that the 12/7-pole Π-core DSPM motor possesses higher average torque output capability and lower torque ripple compared with the 12/8-pole E-core counterpart. Finally, a 12/7-pole Π-core DSPM motor is built and tested so as to experimentally verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of fractional-slot concentrated-windings for use with direct liquid cooling. To achieve considerably higher torque density than state of the art of electrical machines, recently patented cast coils that allow slot fill factors up to 90% are considered as basis for further enhancement. The sensitivity of large conductors to high losses due to current displacement as well as the implementation of direct liquid cooling of every single conductor is discussed. Two innovative coil designs are developed and compared, in consideration of current displacement using finite element methods, with basic trapezoidal cast coils. The heat dissipation capacities of the new coil designs are tested analytically as well as by measurement. Additionally, different cooling mediums are compared for their suitability for direct liquid cooling of coils. The proposed coil designs lead to possible current densities of 100Amm2 and to a reduction of the additional losses to about 50%. [ABSTRACT FROM AUTHOR]

This paper presents a novel consequent-pole hybrid brushless wound-rotor synchronous machine (CPH-BL-WRSM). The proposed machine employs permanent magnets (PMs) on the alternate poles of the salient pole rotor, which has considerably less magnet usage compared to the regular (PM) assisted synchronous machine. The proposed CPH-BL-WRSM offered the advantages of high starting torque, high torque density, and better performance under full-load conditions. The BL operation for the proposed machine is achieved by generating a composite magneto motive force (MMF) with a fundamental component and sub-harmonic component. The sub-harmonic component of the stator MMF is used for BL excitation of the rotor. The finite-element method was used to analyze the performance of the CPH-BL-WRSM in comparison with the performance of the existing BL-WRSM and regular PM-assisted BL-WRSM. Finally, a prototype of the CPH-BL-WRSM was manufactured and the experiment was conducted to demonstrate the performance of the proposed CPH-BL-WRSM. [ABSTRACT FROM AUTHOR]

This study investigates the accurate modelling and the modal natural frequencies of the stator system of a permanent magnet synchronous motor with concentrated winding used in the in-wheel motor system of the electric vehicle. The equivalent material physical properties of each component in the stator system are determined by the correction formula and the empirical coefficient. Meanwhile, the contact conditions between each component are also analysed. According to the structural analysis of stator system, different equivalent finite-element models of winding and frame, together with their effects on the accuracy of simulation results, have been built and investigated, respectively. In addition, the prototype of the motor is fabricated; then the experimental modal analysis of the stator system and its subassemblies are carried out during the manufacturing process. Through comparisons of the results between experiments and finite element anaysis (FEA), the final model of the stator system is determined and verified to be of high accuracy to predict the vibration behaviours of the investigated motor with concentrated winding. Finally, several factors influencing the modal frequencies of stator system are analysed, which could provide certain reference value to the structural design of stator system. [ABSTRACT FROM AUTHOR]

A novel decoupling model for a six-phase permanent magnet machine is proposed in this paper. The model considers the machine as two independent three-phase stator windings that are spatially shifted by a generic angle α . The proposed transformation considers the zero sequence and allows the coupling between phases to be eliminated. The parameters, which define the dynamic behaviour of the model, are calculated with simulations performed using the finite-element method. The decoupled model and the parameters are analyzed for two configurations of a traditional six-phase machine. Simulation results were validated by experimental results with a simple procedure. [ABSTRACT FROM AUTHOR]

This paper adopts simple analytical modeling to investigate the contribution of air-gap field harmonics to the torque production in some three-phase, 12-slot/8-pole doubly salient synchronous reluctance machines (DSRMs) with both conventional and mutually coupled winding configurations. The air-gap flux density has been calculated based on the analytically obtained magnetomotive force and doubly salient air-gap permeance for both the double-layer and single-layer DSRMs with different winding configurations. Then, the contribution of different air-gap 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 DSRMs, the 10th-order harmonic in the double-layer conventional winding (DLC), the 4th-order harmonic in the double-layer mutually coupled winding (DLMC), the 7th-order harmonic in the single-layer conventional winding (SLC), and the 10th-order harmonic in the single-layer mutually coupled winding (SLMC) have the highest contribution to positive average torque and 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. [ABSTRACT FROM AUTHOR]

Frequency response analysis (FRA) is an effective approach for detecting mechanical damage in the windings of a transformer. However, the application of FRA to estimate the winding condition of autotransformers (ATs) employed in the China High-Speed Railway is problematic. Because the split windings of the ATs are connected inside the tank, it is impossible to measure the FRA curves for each split winding outside the tank directly. Therefore, it is difficult to identify fault winding and effectively diagnose the overall condition of the windings. This paper explores the features of FRA curves under different fault conditions to help distinguish the fault winding. An equivalent circuit model is built for the AT with split windings, and the electrical parameters of the windings are determined using the finite-element method. The model is then employed to simulate typical axial displacement faults. The results show that the first antiresonance and resonance of the frequency response for connections involving series windings or series and common windings may be visible features for diagnosing winding faults and the fault level. Specifically, the first and second resonances of the frequency response for the common winding connection may be regarded as the primary feature for identifying fault windings. [ABSTRACT FROM PUBLISHER]

This paper presents a nonlinear analytical model of a multi-V-shape interior permanent magnet (IPM) motor with nonoverlapping concentrated winding. The model relies on Ampere's theorem and the flux conservation law in order to compute the flux density in the different parts of the motor. This article proposes a saturated analytical model of the stator and the rotor. The analytical model is used to calculate the average torque, the power factor, and the voltage of the motor. It is five times faster than the 2-D finite element analysis (FEA). The results are compared with 2-D FEA simulations and experimentally validated using a prototype motor. [ABSTRACT FROM PUBLISHER]

This paper studies the design of electric machine windings with reduced magnetomotive force (MMF) space harmonic content by adjusting the slot distribution and coil turns. Closed-form expressions for the winding factor and harmonic magnitudes established from a mathematical representation of winding functions are used to formulate the MMF space harmonic suppression problem. The framework is applicable to both distributed windings and fractional-slot concentrated windings (FSCWs) and can be solved with different techniques. No special requirements on the slot/pole combination and the number of layers are necessary. One example uses a linear algebraic technique to solve simultaneous equations and the result is a mixed-layer distributed winding. The process also reveals the criterion when multiple requirements on the winding factor and harmonic magnitudes can be satisfied concurrently. Contour plots are included to provide additional graphical insight. Another example designs a 24-slot 22-pole FSCW subset with numerical optimization. The resultant winding is a four-layer FSCW with two subsets and 3/4 of the harmonic orders are eliminated. The performance improvement of this winding is verified with finite-element simulations. [ABSTRACT FROM PUBLISHER]

A comparison between unbalanced distributed winding and balanced concentrated winding is presented in this paper. The application is a torque motor where low speed and high torque are main requirements. Concentrated winding slot/pole combination is selected so that winding factor is maximum and as well as it is equal to the winding factor of the unbalanced winding motor. Stator and rotor Magneto-Motive Force (MMF) functions are obtained for both motor types to model torque ripple components in the frequency spectrum. Finite element analysis (FEA) and experimental results are presented to compare back EMF waveforms, magnetic loading, torque constant and thermal performance of two motors. Two designs have identical stator outer diameter (OD) and active axial length. The detailed comparison shows that two motors have similar torque constant. The behavior of two motors under heavy load differs and concentrated winding design performs better. Thermal performance of the designs is also compared and it is observed that concentrated winding design has also less winding temperature rise. [ABSTRACT FROM AUTHOR]

Abstract: There is growing interest in superconducting machinery design in AC regime such as generators, motors, and magnets. High‐temperature superconductors are used as tapes or cables for the machine windings. Therefore, AC losses have to be evaluated efficiently for an optimal design. Moreover, non‐linearities, arising from the power law characterizing the electrical behaviour of superconductor, have to be also dealt with. The development of efficient numerical methods is therefore critical to model high‐temperature superconductors. Although numerous methods have already been proposed, the finite element method applied on the time‐dependent curl‐curl–based H‐formulation remains the mostly used. It uses edge elements of Nedelec to naturally ensure the continuity of the tangential components of H. To take into account non‐linearities from superconductors, a linearisation of the superconductors constitutive power law E=ρ(J)J was implemented. Discontinuous Galerkin finite element method provides an interesting alternative to edge elements for the time‐dependent H‐formulation. Indeed, the curl‐curl operator is written as a div operator and the interior penalty approach defines numerical fluxes at the interfaces. Those fluxes will ensure the continuity of the tangential components of H. The resistivity ρ(J) is explicitly evaluated at the previous iteration with such an approach leading to convergence. In this paper, both numerical approaches implementation will be presented. We will also compare the numerical results from those methods applied to 3D modelling of simple superconducting geometries in AC regime. [ABSTRACT FROM AUTHOR]

This paper deals with the harmonic-balance (HB) finite-element (FE) analysis of a multi-turn winding device coupled to electrical circuits comprising nonlinear components. The eddy-current effects in the windings are accounted for via a frequency-dependent reluctivity and impedance determined with a homogenization technique. The proposed multi-frequency approach is validated through a single-phase four-diode rectifier with an axisymmetric FE model of an inductor. The system of nonlinear algebraic equations is solved by means of the Newton–Raphson method. The HB results are validated with classical time-stepping simulations. The computational cost is briefly discussed. [ABSTRACT FROM AUTHOR]

The paper discusses the method of a description of the magnetic field sources in systems with the stranded windings. The sources are determined on the basis of an obtained distribution of edge values of the current vector potential T0. The formulas describing the magnetic field sources in the finite element (FE) space for the formulations using the scalar potential F and the vector potential A have been given. The approach for determining the T0 distribution in the stranded windings of simple and complex geometries has been proposed. [ABSTRACT FROM AUTHOR]

The aim of this study is to analyze the vibration behavior of a five-phase flux switching machine in order to detect and discriminate full and partial open-phase faults. To achieve our goal, radial magnetic stress was calculated by two magnetic models. The first magnetic model, presented in this paper, is obtained by finite element analysis (FE) and the second one by permeance network analysis (PN) of the studied electrical machine. Stator radial accelerations were evaluated coupling each of the two magnetic models with an analytical mechanical model. The results of two multiphysics models are compared with experimental results, in order to validate them. Experimental measurements are performed under healthy and faulty conditions, at fixed rotational speed. For faulty conditions, full open-phase and partial open-phase fault of the stator winding were analyzed. [ABSTRACT FROM AUTHOR]

A uniform energy control strategy for single-phase AC resistance spot welding (RSW) was proposed in this paper. Through seriously analyzing the welding process, a variable, which is the product of square of welding current and welding time ( I t), can be considered as an ideal control variable to ensure the uniform energy delivery. It can be translated to constant current control in reality. However, when the winding ratios of the welding transformer are different, direct translation can obtain incorrect result. Then, the effect of different winding ratios on welding current was studied, and a method which can obtain a corresponding constant welding current when different number of windings were employed was proposed. Final simulation and corresponding analysis validated the proposed method, and the method can be employed to facilitate the current welding production. This work provides a convenient and effective method for welding control when different ratios of welding transformer are employed. [ABSTRACT FROM AUTHOR]

To meet the high requirements in transport systems, permanent magnet linear synchronous motor (PMLSM) has become an important field of research. A novel trilateral PMLSM with slotless ring windings is proposed, featuring high thrust and low ripple. The structure design of the novel trilateral PMLSM is introduced first. Then mathematical model of the primary with slotless ring windings is established and analysed, the magnetic fields excited by the permanent magnets in the secondary is studied, based on the equivalent magnetising current method. The analytical calculating results of the novel motor are validated by finite-element method, and a prototype is tested to validate the analytical results of this novel motor. The study provides the fundamental characteristic analysis of the novel trilateral PMLSM with slotless ring windings. This study is provided for the special section 'Design, modeling and control of electric drives for transportation applications' (VPPC 2016). [ABSTRACT FROM AUTHOR]

This paper presents a new axial flux permanent magnet machine, named ring winding axial flux machine (AFM). The ring winding AFM (RWAFM) takes the advantage of segmented stator of yokeless and segmented armature topology with those of decoupled phases and ring winding of transverse flux topology. In this paper, the geometry of the RWAFM is introduced in detail. Furthermore, the working principle and torque production theory are discussed. To validate the concept and confirm manufacturability of the proposed topology, a prototype is fabricated. The performance of the RWAFM is studied through experimental tests, 3-D finite-element simulations, and analytical discussions. [ABSTRACT FROM PUBLISHER]

SUMMARY In this paper, a new hybrid-excited motor is proposed. Its unique feature is that it has no field exciting coil, despite being a type of bypass yoke core (BYC) hybrid-excited synchronous motor. Based on finite element analysis (FEA), the following facts are clarified. Since the stator coil magnetomotive force (MMF) and claw poles rotate at the same speed and in the same direction, they are motionless relative to each other. Since the claw poles are located at one of its ends near the BYC surface with a gap, it receives immovable magnetization by the stator coil MMF through the BYC; then the claw poles can supply a magnetic field flux via the BYC. This flux via the BYC increases the total torque, because its torque is added the two other torque components: the permanent magnet torque and claw poles reluctance torque. In addition, the magnetic polarity and the amount of the flux of the claw poles can be varied by controlling the armature current phase angle. [ABSTRACT FROM AUTHOR]