Winding Topology Research Articles

Performance improvement of a three phase induction squired-cage motor by winding topology configuration

The aim of this paper is to determine the optimal stator winding topology configuration for a 75 kW three-phase squirrel cage motor that provides the highest efficiency, power factor, and optimal starting parameters. The induction motor is simulated using Cedrat FLUX2D finite element software, which enables accurate modeling of its performance. Initially, the motor operation is simulated using the originally manufactured winding topology. Then, several alternative winding topology configurations are tested through numerical simulations. The performance results for each configuration are compared with those obtained from the original winding topology to identify the best option. The simulation results show that the shortened pitch concentric winding, combining both single and double layers, is the winding topology that offers the highest performance for the motor under study, significantly enhancing the overall efficiency of the system. These findings highlight the potential of optimized winding configurations in improving motor performance and energy efficiency.

Non-Abelian Braiding of Topological Edge Bands.

Braiding is a geometric concept that manifests itself in a variety of scientific contexts from biology to physics, and has been employed to classify bulk band topology in topological materials. Topological edge states can also form braiding structures, as demonstrated recently in a type of topological insulators known as Möbius insulators, whose topological edge states form two braided bands exhibiting a Möbius twist. While the formation of Möbius twist is inspiring, it belongs to the simple Abelian braid group B_{2}. The most fascinating features about topological braids rely on the non-Abelianness in the higher-order braid group B_{N} (N≥3), which necessitates multiple edge bands, but so far it has not been discussed. Here, based on the gauge enriched symmetry, we develop a scheme to realize non-Abelian braiding of multiple topological edge bands. We propose tight-binding models of topological insulators that are able to generate topological edge states forming non-Abelian braiding structures. Experimental demonstrations are conducted in two acoustic crystals, which carry three and four braided acoustic edge bands, respectively. The observed braiding structure can correspond to the topological winding in the complex eigenvalue space of projective translation operator, akin to the previously established point-gap winding topology in the bulk of the Hatano-Nelson model. Our Letter also constitutes the realization of non-Abelian braiding topology on an actual crystal platform, but not based on the "virtual" synthetic dimensions.

Construction and Observation of Flexibly Controllable High-Dimensional Non-Hermitian Skin Effects.

Non-Hermitian skin effect (NHSE) is one of the most fundamental phenomena in non-Hermitian physics. It is established that 1D NHSE originates from the nontrivial spectral winding topology. However, the topological origin behind the higher-dimensional NHSE remains unclear, which poses a substantial challenge in constructing and manipulating high-dimensional NHSEs. Here, an intuitive bottom-to-top scheme to construct high-dimensional NHSEs is proposed, through assembling multiple independent 1D NHSEs. Not only the elusive high-dimensional NHSEs can be effectively predicted from the well-defined 1D spectral winding topologies, but also the high-dimensional generalized Brillouin zones can be directly synthesized from the 1D counterparts. As examples, two 2D nonreciprocal acoustic metamaterials are experimentally implemented to demonstrate highly controllable multi-polar NHSEs and hybrid skin-topological effects, where the sound fields can be frequency-selectively localized at any desired corners and boundaries. These results offer a practicable strategy for engineering high-dimensional NHSEs, which can boost advanced applications such as selective filters and directional amplifiers.

AC Losses Analysis and Design Guidelines for Hairpin Windings With Segmented Conductors

In the last years, hairpin windings are amongst the most studied and implemented winding topologies to increase torque and power densities of electrical machines, especially in the traction field. However, their main drawback remains the elevated ohmic losses generated at high frequency operations. Recently, hairpin windings with segmented conductors have been proposed to overcome this challenge, but an analytical model to predict the losses in such unconventional winding is missing, as well as a critical analysis on the extra manufacturing complexities needed. In this paper, first a simple analytical formulation for the estimation of AC losses in segmented hairpin conductors is proposed, developed and validated at various operating frequencies, both through finite element analyses and experimental measurements. Then, an in-depth analysis of the main advantages and disadvantages of this winding topology is proposed with the aim at providing guidelines and recommendations for their practical realization, adopting standard methodologies for their connection and transposition.

Simplified Phase Model Predictive Voltage Control for Half-Centralized Open-End Winding Permanent-Magnet Motor Systems

In order to obtain a wider speed range for the permanent-magnet linear motor drive system, a half-centralized open-end winding (OEW) topology is studied. In this topology, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> movers are supplied by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> +1 voltage-source-inverters (VSIs), and all these VSIs share a common dc bus voltage. In order to reduce the computation burden, a simplified phase model predictive voltage control (S-PMPVC) is proposed in this paper. For S-PMPVC, the optimal and suboptimal base levels are defined. When the optimal base level cannot be implemented, the suboptimal base level is selected. As a result, S-PMPVC requires smaller computation burden while the performances are not degraded. By taking the advantage of the smaller computation burden, S-PMPVC can adopt higher control frequency to improve performances. The effectiveness of S-PMPVC has been verified by simulation and experimental results.

Comparison of concentrated winding topologies considering transient voltages in the winding system of inverter-driven low-voltage machines

Comparison of concentrated winding topologies considering transient voltages in the winding system of inverter-driven low-voltage machines

Novel Dual Inverter Sub-Harmonic Synchronous Machines

Sub-harmonic synchronous machines are a relatively new bread of brushless wound field synchronous machines considered alternatives to many electric machines in transportation electrification applications. This paper presents two dual inverter sub-harmonic synchronous machines having unique two-layer and three-layer stator winding topologies. The two inverters provide the stator windings with two sets of balanced three-phase currents. These two and three-layer windings are arranged in such a way that they can generate both fundamental and sub-harmonic magnetomotive force. Furthermore, the fundamental MMF component of this machine is four times the sub-harmonic MMF component used for the brushless operation. In contrast, the sub-harmonic magnetomotive force is used for field excitation, which leads to brushless operation. Two 8-pole, 48-slot, 2-inverter, 2-layer and 3-layer sub-harmonic machines are designed to validate the concept through a 2-D finite element analysis of these new topologies, showing a better overall torque profile and performance as compared with the other sub-harmonic and brushless wound field synchronous machines.

Winding Loss Suppression in Inverter-Fed Traction Motors via Hybrid Coil Materials and Configurations

In a typical inverter-fed AC drive system, the stator windings carry a current with a large harmonics content, resulting in an increased AC loss. In this paper, the additional copper losses caused by non-sinusoidal currents are investigated for different magnet wire topologies, including the flat conductor, stranded, and litz wires. Also, a two-slot simplified model is introduced for accurate prediction of the AC losses at high frequency. It is found that one of the major issues of the conventional copper coil is that the losses are not uniformly distributed across the slot, and over 70% of the losses are concentrated near the slot opening. Moreover, using the transient finite element method, different winding topologies and arrangements are simulated at the stranded level to evaluate the losses and current density for each strand under highly distorted currents. Furthermore, different coil samples are prototyped for the same slot geometries to compare their performance under the same pulse-width modulation (PWM) waveforms for a wide range of frequencies. Finally, new hybrid coil topologies are proposed, which employ different magnet wires or materials within the same slot. The results demonstrate that utilizing a mixed wire configuration can effectively mitigate the adverse effects of eddy current losses. This approach can yield up to 16–41% lower losses while also achieving a weight savings of 36–70%.

Circulating and Eddy Current Losses in Coreless Axial Flux PM Machine Stators With PCB Windings

Printed circuit board (PCB) stators in coreless axial flux permanent magnet (AFPM) machines have been proposed, designed, and studied for use in multiple industries due to their design flexibility and reduction of manufacturing costs, volume, and weight compared to conventional stators. This paper investigates mechanisms and methods of approximating open circuit losses in PCB stators within example wave and spiral winding topologies for a dual rotor, single stator configuration using 3D FEA, analytical hybrid techniques and experiments. The effect of rotor magnet shape, end winding, and active conductor geometry on eddy currents is studied, and some mitigation techniques are proposed. Through stator equivalent circuit analysis, circulating current losses caused by mechanical abnormalities and magnetic circuit asymmetry are assessed. Possible strategies and schemes to minimize circulating current losses are also described. The trade-off between stator loss components and some practical design considerations are outlined in detail. The open circuit power losses of a prototype coreless AFPM motor were experimentally tested using multiple example PCB stators and emulated rotor asymmetries, with the findings being comparable to the FEA and hybrid analytical methods results.

Design of Limited-Angle Wound Rotor Resolvers for High Accuracy and Easy Manufacturability

The limited-angle resolver is commonly employed instead of an optical encoder as a position sensor in medical, special industrial, custom robotics, transportation and military applications owing to their reliability, low cost, and ability to work steadily in harsh and contaminated environments. In the design and optimization of resolvers, achieving high precision while maintaining a simple manufacturing process for mass production is a big challenge. This study proposes a systematic method for the determination of slot and pole number combinations of limited-angle wound rotor resolvers (LAWRRs) for high accuracy and easy manufacturability. A set of stator and rotor slot numbers ranging from 8–64 for 2 and 4 poles, which are suitable for concentric winding (CW) topology, have been considered. For high accuracy, number of turns distribution waveforms and their total harmonic distortion (THD) percentages are investigated. In addition, for easy manufacturability, low slot number combinations providing high accuracy are determined and the feasibility of employing solid core instead of laminated core is examined. Analytical calculation results of the proposed configurations are validated utilizing a two-dimensional time-stepping finite-element analysis (2D-FEA). Finally, in order to experimentally validate the methodology and analyses, two prototypes with low and high slot numbers are manufactured and tested.

Switchable optical vortex beam generator based on an all-dielectric metasurface governed by merging bound states in the continuum.

The polarization topology around the bound states in continuum (BIC) affects the optical vortex (OV) beam generation. We propose a cross-cross-shaped resonator based on a THz metasurface to realize an OV beam generator in real space by exploiting the inherent winding topology around the BIC. The BIC merging at the point Γ is achieved by tuning the width of the cross resonator, which significantly improves the Q factor and enhances the field localization. Furthermore, the switching between the high-order OV beam generator governed by the merged BIC and the low-order OV beam generator is realized. This extends the application of BIC in modulating orbital angular momentum.

Performance Evaluation and Comparison of Three-Phase and Six-Phase Winding in Ultrahigh-Speed Machine for High-Power Application

This article investigates the influence of multiphase winding topologies in high-power ultra-high-speed machines (HP-UHSM) of 500 kr&#x002F;min. At this speed level, increasing the rotor&#x0027;s magnetic loading excites its critical bending resonances and leads to structural breakdown. On the other hand, increasing the stator&#x0027;s electric loading using the three-phase winding increases unwanted vibrations in a slotted stator and reduces the electromagnetic inter-action of the stator and rotor in a slotless stator. Consequently, the maximum output power level of UHSM (500 kr&#x002F;min or more) is limited to a few hundred watts only in the state-of-the-art. To over-come such a critical limitation, this article proposes a new design methodology for HP-UHSM, where the rotor&#x0027;s bending resonances and centrifugal stresses are restricted by limiting the maximum aspect ratio (<i>L&#x002F;D</i>), and an optimal multiphase winding is adopted in the slotless stator to increase the power level by effective electric loading. Also, a Multiphysics optimization is utilized to obtain the optimum magnetic loading and electric loading, where the bending resonance and other system limits are defined using multi-disciplinary design constraints. It is observed that the multiphase winding provides an added degree of freedom to increase the power level of UHSM without exciting the rotor&#x0027;s bending resonances and structural breakdown. Using the proposed method, a multiphase 2 kW 500 kr&#x002F;min HP-UHSM has been designed for the safety-critical AMEBA system and compared its Multiphysics performance with the three-phase machine having the same volume. Finally, exten-sive experiments are performed on both prototypes to validate the effectiveness of the proposed method. It is shown that the multi-phase HP-UHSM has no critical bending resonance below the 500 kr&#x002F;min, and it has 16.3&#x0025; higher output power with 1.18&#x0025; higher efficiency and 28.6&#x0025; lower back-EMF than the three-phase design.

Unified Maximum Voltage Utilization Controls for Half-Centralized Open-End Winding Permanent-Magnet Motor Systems

In order to extend the speed range and reduce power electronics devices of the primary permanent-magnet linear motor traction system, a half-centralized open-end winding topology is studied in this article, in which <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> movers are supplied by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> +1 voltage-source inverters. In order to maximize the speed range, two unified maximum voltage utilization control (UMVUC) methods are proposed for the studied traction system, which can be easily implemented for any number of movers. The first UMVUC is named as the original UMVUC, and it requires a heavy computation burden, which makes the implementation difficult when the number of movers is large. For the linear motor system, the relative positions of all movers are approximately constant. Based on this feature, the second UMVUC named as simplified UMVUC is proposed, which can significantly reduce the computation burden. In order to suppress the zero-sequence current (ZSC) and reduce the switching loss, a zero-sequence polarity assignment method is employed in the proposed UMVUCs. An experiment platform is developed, and the effectiveness of the proposed UMVUCs has been validated by experimental results.

Phase Model Predictive Voltage Control for Half-Centralized Open-End Winding Permanent-Magnet Linear Motor Traction Systems

In order to extend the speed range and reduce power electronics devices of the permanent-magnet linear motor traction system, a half-centralized open-end winding topology is studied in this article, in which two movers are supplied by three voltage-source-inverters (VSIs). All these VSIs share a common dc-bus voltage, and the zero-sequence current becomes a challenge. In order to solve cope with this challenge, two phase model predictive voltage controls (PMPVCs) are proposed. Referring to the traditional finite-control-set MPVC (FCS-MPVC), an FCS-PMPVC scheme is proposed and the optimal phase voltage group is determined by minimizing three independent phase cost functions. For FCS-PMPVC, 21 phase voltage group are evaluated while the evaluation number of the traditional FCS-MPVC is 512. In order to reduce the computation burden furthermore, a new concept phase voltage vector (PVV) is defined, and the optimal PVV is directly determined by the nearest distance principle instead of the time-consuming evaluation. The second PMPVC is named as geometrical-location PMPVC (GL-PMPVC). Both PMPVCs have same performances while the computation burden of GL-PMPVC is nearly 47% of that of FCS-PMPVC. The effectiveness of the proposed PMPVCs have been verified by experimental results.

In-wheel, outer rotor, permanent magnet synchronous motor design with improved torque density for electric vehicle applications

In electric vehicle applications, the torque density of electric motor plays an important role in improving the performance of the vehicle. The main objective of this paper is to investigate a possible method for improving the torque density of a permanent magnet synchronous motor used in electric vehicles. At the same time, other machine specifications were taken into account and kept within the acceptable level. This was achieved by incorporating performance enhancement strategies such as investigating ofhigh-efficient winding topology for the motor’s stator to give the highest winding factor and optimizing the machine dimensions to achieve the best performance. MagNet 7.4.1 software package with static and transient finite element method solver was used for implementing the proposed design. The results showed a significant improvement in the torque density with keeping the overall machine performance.

Four-Vector Phase Model Predictive Voltage Control for Half-Centralized Open-End Winding Permanent-Magnet Linear Motor Systems

In order to achieve the purpose of extending the speed range and reducing power electronics devices for the permanent-magnet linear motor drive system, a half-centralized open-end winding (OEW) topology is studied for rail transit applications in this paper. In this topology, compared with the traditional OEW topology, the number of voltage-source-inverters (VSIs) can be reduced from four to three to drive two OEW movers and all these VSIs share a common dc bus voltage. In order to improve the steady-state performances, a four-vector phase model predictive voltage control (FV-PMPVC) is proposed in this paper. Due to the spatial distribution of phase voltage vector (PVV), an orthometric synthesis principle (OSP) is proposed to calculated the duration time for the vector synthesis, which reduces the computation burden and enhances the robustness. Comparing the existing control method, FV-PMPVC can get similar dynamic performances but better steady-state performances. Additionally, the half-centralized topology using FV-PMPVC can have same speed range while less VSIs are required. The effectiveness of FV-PMPVC is verified by experimental results.

Synchronous reluctance machines with new type of fractional‐slot concentrated‐windings based on the concept of stator slot shifting

Fractional-slot concentrated-windings are appreciated for their simple construction, short end-winding length, high copper fill factor, low cogging torque, good field-weakening capability and fault-tolerant ability. However, in comparison to the conventional distributed windings, the fractional-slot concentrated-windings are characterised with high space magnetomotive force (MMF) harmonics, which results in undesirable effects on the machine performance, such as localised core saturation, eddy current loss in the rotor and noise and vibration. In order to improve winding characteristics, several techniques have been developed recently. This manuscript introduces the 5 new winding topologies by using the general concept of stator slot shifting. It means that, in order to cancel undesirable MMF harmonics, by doubling (or tripling or even multiplying) the slot number and dividing the winding and then relatively shifting the winding by one (or more) slots, the undesirable harmonics have been eliminated effectively. The best choice is chosen according to the lowest amount of the MMF harmonic, highest value of winding factor and torque desirable characteristics. At the end, comprehensive comparisons for the designed synchronous reluctance motor (SynRel) equipped with proposed windings and also distributed winding are presented. The analytical study and 2D FEM analysis results show that it is possible to get an ideal low space-harmonic winding topology, and consequently, a low torque ripple for these motors.

Electrical Machines Winding Technology: Latest Advancements for Transportation Electrification

The ever-increasing demand for higher-power dense electrical machines has resulted in different electrical, mechanical, and thermal stresses, which can eventually cause machine failure. For this reason, the management of stresses and losses must be thoughtfully investigated to have a highly reliable electrical machine. The literature agrees that winding losses are the dominant loss mechanism in many electrical machines. However, statements vary on how to mitigate these losses along with the aforementioned stresses. To avoid winding failure, a study of the various winding topologies would allow for a better consideration of the challenges and limitations in the performance of different electrical machines. To this aim, this paper introduces a comprehensive review for different winding topologies. Many reported cases in the literature are summarized and compared. Moreover, the utilization of additive manufacturing (AM) in the production of the machine windings is presented, showing a high level of maturity of this emerging technology. Finally, different challenges facing the design of machine windings are introduced including the AC high frequency losses, thermal management, mechanical and acoustic problems, insulation aging, automated production, and winding manufacturability.

Hybrid-Strand Winding Topology With Improved Power Density in Automotive Electric Machines

The rectangular profile conductor with a large cross section requires less slot space and has better heat dissipation ability than the traditional round profile one. But its application in automotive propulsion electric machines is thwarted by high ac winding losses and temperature rise under high-speed operations. This article proposes a novel stator winding topology with hybrid strands based on the ac losses' distribution characteristics and the theoretical relationship between the eddy current suppressing ability and the geometric parameters. The new winding can effectively reduce the ac loss and the peak temperature in the winding at high-speed operation. Meanwhile, it can maintain a high filling rate. Therefore, the machine's maximum rotating speed and power density can be effectively improved. In experimental validation, a winding sample with this new topology is manufactured and compared with the conventional one formed by rectangular wires. It shows the proposed method can reduce the winding ac loss by up to 12% and the temperature rise by 10–21%. It is validated to have considerable industrial potential in the future development of automotive motors.

Calculation of Rotor Harmonic Losses in Multiphase Induction Machines

The topic of this paper is the determination of rotor harmonic losses in multiphase machines. Specifically, harmonic losses occur in the rotor winding and core due to higher-order spatial harmonics of the flux density. This phenomenon influences machine parameters and overall performance and increases temperature rise in parts of the rotor. The flux density distribution is determined by the stator magnetomotive force harmonic content, which is directly related to the winding distribution. A cage-rotor asymmetrical six-phase induction machine is selected for this case study. An analysis of different stator winding topologies and their influence on harmonic losses is presented. A finite element-based method for calculating the contribution of individual stator magnetomotive force harmonics to the rotor losses is developed and described in the paper. The analysis includes scenarios with different phase current waveforms to emphasize the issues specific to the asymmetrical six-phase machine. It is found that the magnetomotive force components generated by non-torque-producing current components contribute significantly to harmonic losses. The obtained results can represent a foundation for optimal stator winding topology selection. This work is intended to motivate the development of new and the modification of existing models to properly include rotor harmonic losses during the design, performance prediction, and control of multiphase machines.