Non-overlapping Windings Research Articles

Electromagnetic and Mechanical Stress Analysis of a 5 MW High-Pole Non-Overlap Winding Wound-Rotor Synchronous Wind Generator

Electromagnetic and Mechanical Stress Analysis of a 5 MW High-Pole Non-Overlap Winding Wound-Rotor Synchronous Wind Generator

Investigation of Permanent-Magnet Vernier Machine With Fractional-Slot Nonoverlapping Windings for Direct-Drive Application

Investigation of Permanent-Magnet Vernier Machine With Fractional-Slot Nonoverlapping Windings for Direct-Drive Application

Normal and Faulty Performance Analysis of Non-Overlap Winding Technologies of a Large Wound Rotor Synchronous Generator for Wind Energy Conversion

Normal and Faulty Performance Analysis of Non-Overlap Winding Technologies of a Large Wound Rotor Synchronous Generator for Wind Energy Conversion

Magnetic Coupling Effect and Performance Analysis of Dual Rotor Permanent Magnet Flux Switching Generator for Counter Rotating Wind Power Generation

To eliminate slip rings, brushes, and terminate gear-box mechanism, ferrite permanent magnet (PM) based counter rotating dual rotor PM flux switching generator (CRDRPMFSG) for direct drive counter rotating wind turbine (D <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> CRWT) application is proposed in this paper. Initially, the mechanism of gearless and brushless counter rotating wind power generation is discussed, and a simplified formulation opted for the slot/pole combinations. The proposed CRDRPMFSG encapsulate inner and outer machines with circumferentially magnetized PM enclosed by non-overlapped armature windings; thus, offering reduced overhang with compact design. However, co-axially linking the inner and outer machines through a shared stator yoke results in serious issues of magnetic coupling due to dual air-gap fields. To this end, eight topologies with various slot/pole combinations are comprehensively investigated using finite element analysis (FEA) for magnetic coupling effects and its influence on electromagnetic performance. From the analysis, it is shown that magnetic coupling level influence electromagnetic performance i.e., average torque, ripple rate, power factor, efficiency, losses, and output power. Moreover, it is noted that coupling level can be reduced by adopting same stator teeth in inner and outer machines or same stator teeth with different rotor poles. Finally, the predicted FEA calculations are verified experimentally with four benchmarked CRDRPMFSG prototypes.

Flux Reversal Permanent Magnet Machines With Single-Layer Non-Overlapping Windings

Single-layer (SL) non-overlapping windings are applied to flux reversal permanent magnet (FPRM) machines, to extend the family of stator-PM machines. The machine topology and operating principle are introduced, and the general rules of symmetrical phase flux-linkages in machines with various slot/pole number combinations are found. The even order coil flux-linkage harmonics can be cancelled in the resultant phase waveforms due to opposite polarities of either magnets or coils. Moreover, based on finite element (FE) analysis, the FRPM machines with different rotor pole numbers, equipped with SL or double-layer (DL) windings, are comprehensively compared. The results reveal that compared to their DL counterparts, the FRPM machines with SL windings (FRPM-SL) exhibit similar torques and iron losses, as well as enhanced flux-weakening and fault-tolerant capabilities due to higher self-inductances but lower mutual-inductances. A pair of FRPM-SL prototype machines are manufactured and tested to validate the predictions.

Improved Coreless Axial Flux Permanent-Magnet Machine With Nonuniformly Distributed Winding

The windings of coreless axial flux permanent-magnet machine (CAFPM) are exposed to the rotor magnetic field, where each back electromotive force (EMF) harmonic is induced not only by several different spatial field harmonics but also by the winding distribution. In order to reduce the time harmonics of back EMF for CAFPM with non-overlapping winding, one new winding structure with non-uniform distributed coils is proposed in this paper, in which the coils are arranged in a non-uniform way with annular distribution in the stator. Firstly, the relationship between uniform and non-uniform distributed windings is analyzed based on the phasor diagram of each coil EMF, and the analytical expression of back EMF under non-uniform distributed windings is established. Secondly, key performance indexes under different working states, like no-load, are investigated by three dimensional (3-D) finite element analysis (FEA). Finally, comprehensive experiments are carried out to verify related theoretical analysis, which demonstrate that the non-uniform distributed windings can effectively reduce the time harmonics and increase the working efficiency.

Performance Comparison of Large-Scale Design-Optimized Non-Overlap and Overlap Winding Wound Rotor Synchronous Generators

The use of non-overlap windings rather than overlap windings is a topic for debate. Non-overlap windings are generally cheaper and easier to manufacture but result in a high amount of magnetomotive force sub- and higher-order harmonics. A strategy to reduce these harmonics has been previously published and this study aims to provide a performance comparison of a large-scale wound rotor synchronous generator with a modified non-overlap winding and a classical overlap winding. Hence, design optimisations of a 16/18 and 16/72 pole/slot grid-connected 3 MW wound rotor synchronous generator for medium-speed wind generation are conducted. The optimisations are performed using the modified method of feasible direction gradient-based optimisation because of its simplicity and fast results. Optimal solutions for the 16/18 and 16/72 3 MW models are obtained and the performance of the solutions compared. The results show that the 3 MW 16/18 model performs favourably against the 3 MW 16/72 model, especially regarding the lower active mass.

Modeling and Current Control Strategy for Novel Two-Phase DC-Biased Vernier Reluctance Machine

This paper proposes a drive topology and vector control strategy for a two-phase DC-biased vernier reluctance machine (DCB-VRM) with non-overlapping windings. Since the DC path needs to be reserved in the DCB-VRM drive topology, more power switching devices are needed in theory. In order to generate DC bias sinusoidal current and reduce costs, a low-cost drive topology is applied. The machine's mathematical model in the stationary and synchronous rotating frame is derived. Then the vector control strategy is proposed. Through effective control of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dqdc</i> -axis currents, maximum torque per ampere (MTPA) can be achieved. The resonant controllers are paralleled with the proportional-integral (PI) controller to suppress current harmonics in the control method. Finally, the simulation and experimental results validate that the proposed drive topology and control strategy can effectively control the two-phase DCB-VRM.

High efficiency flux switching motor

Flux switching motor (FSM) with field excitation is permanent magnet free and attractive for many industrial and domestic applications. However, design with the conventional trapezoidal stator slot has low efficiency and always been a challenge in the state of the art. Further, the finite element analysis (FEA) method for the electromagnetic performance investigation is a powerful tool, but, it has high computational time, computational complexity and drive storage. To address the concern of low efficiency, in this paper, a new single phase 8slots–6poles electrically excited (EE) FSM design with the rectangular stator slot (RSS), salient rotor and non-overlapped windings for pedestal fan applications is been proposed. The proposed RSS EEFSM design is analyzed analytically and the analytical results are validated by FEA method. Finally, experimental test of the proposed EEFSM prototype is performed. The measured results are in a good agreement with the calculated results. Moreover, the proposed RSS EEFSM has higher efficiency as compared to the conventional design.

Performance Analysis of an Outer Rotor Variable Reluctance Resolver

Variable reluctance resolver (VR-Resolver) is a robust electromagnetic sensor that provides position information for closed-loop control systems of permanent magnet synchronous motors (PMSMs). For specific motion control applications, an outer rotor structure is presented for the VR-Resolver in this article with a nonoverlapping tooth-coil windings configuration to simplify the manufacturing process. The study on the structure of the proposed position sensor is carried out, followed by the description of the working principle. The presented outer rotor VR-Resolver is simulated and its performance is investigated in detail with the aid of transient finite-element analysis (TFEA). Sensitivity analysis is carried out on the rotor shape factors and slot opening, and the effect of manufacturing tolerances is investigated as well. Finally, the effectiveness of the optimal design is verified by 3-D TFEA.

Comparative Study of Permanent Magnet, Conventional, and Advanced Induction Machines for Traction Applications

This paper investigates and compares the torque-generating capabilities and electromagnetic performance of advanced non-overlapping winding induction machines (AIM), conventional induction machines (CIM), and interior-permanent magnet (IPM) machines for electric vehicle (EV) applications. All investigated machines are designed based on the specifications of the Toyota Prius 2010 IPM machine. The steady-state and flux-weakening performance characteristics are calculated by employing the 2D finite element method and MatLab, and the obtained results are quantitatively compared. Furthermore, the torque-generating capabilities of three machines are investigated for different electric loadings, and the machine having the highest torque-generating capability is determined as AIM. Moreover, the major parameters affecting the torque-generating capability, such as magnetic saturation and magnet demagnetization, are examined in depth.

Comparison of Electromagnetic Performance according to Winding Configuration for Modular Dual 3-Phase Permanent Magnet Machines

A new winding structure for modular dual 3-phase permanent magnet machine, which makes it possible to reduce mutual coupling between two-winding sets of inverters and interference between phases that belong to the same inverter has been proposed in this study. The modular dual 3-phase system with overlapping winding technique has been widely employed in large-scale machine applications such as wind power production; however, its drawbacks include large torque ripple, long end-winding, and large magnetic mutual interference. To address these problems, a new modular dual 3-phase winding can be achieved by replacing adjacent redundant coils in one of the same phase coils with nonoverlapping winding. For clarity, three dual 3-phase machines are selected to examine their differences. The first is 32-poles/96-slots adopting a conventional overlapping modular winding (

Electromagnetic Performance Analysis of 6-Slot/2-Pole High-Speed Permanent Magnet Motors With Coil-pitch of Two Slot-pitches

In this paper, a high-speed permanent magnet (HSPM) motor having 6-slot/2-pole (6s/2p) number combination and 2 coil-pitch windings are developed for domestic appliance application. Two HSPM motors with different layouts of 2 coil-pitch windings are optimized and their electromagnetic performances are evaluated. The best winding configuration is then identified for shorter motor axial length and larger torque density. Since 3-slot/2-pole (3s/2p) HSPM motors with non-overlapping windings have the same winding factor, a comparison between 3-slot and 6-slot motors is also conducted, particularly for torque density, losses, and unbalanced magnetic force (UMF). It shows that 6s/2p PM motors with 2 coil-pitch windings are suitable for high-speed application without UMF and less rotor PM loss. Finite element predicted electromagnetic performances are validated by experiments made on two prototype motors.

Axial-Field Synchronous Machine With HTS Armature Windings: Realization and Preliminary Tests

The realization and preliminary tests of a high temperature superconducting axial-field synchronous machine (HTS-AFSM) prototype are presented in this paper. The HTS machine consists of a 3-phase stator with HTS armature winding and a permanent magnet (PM) rotor. The HTS armature winding contains three pancake coils made of BSCCO tape forming a single layer nonoverlapping concentrated stator windings. The rotor is composed of four NdFeB permanent magnets. Several tests have been carried out such as voltage vs. currents curves of the HTS coils, static torque, back-EMF and load tests in generator mode. A 3D semi-analytical model, based on integral equations, has been used to check out the measured electromagnetic quantities. It has been shown that the measured and the calculated quantities are in satisfactory agreement.

Analytical Prediction of the MCSA Signatures Under Dynamic Eccentricity in PM Machines With Concentrated Non-Overlapping Windings

This paper proposes a novel algorithm which made it feasible to predict the harmonic fault signatures under dynamic eccentricity in Permanent-Magnet synchronous machines with concentrated non-overlapping winding for any slot-pole combination. In the literature, only the appearance of the fractional harmonic components related with the pole number has been proposed but there are no studies to predict which exact components will rise in each topology. Initially, a mathematical equation is derived for the machine <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">EMF</i> under dynamic eccentricity based on the air gap permeance model. Later on, the terms of this equation are inserted in a Fault Signature Block Binary Array in which the position of each cell expresses a specific harmonic frequency component. After substitution of the machines parameters, the array results with zero and nonzero terms. The positions of the nonzero terms express the frequency components excited by this particular fault. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3-D</i> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FEA</i> and experimental results of a Permanent-Magnet Axial-Flux Machine are used to validate the proposed algorithm.

Performance Investigation and Cogging Torque Reduction in a Novel Modular Stator PM Flux Reversal Machine

In this research paper, various performances of five different rotor pole topologies of the proposed novel modular stator (MS) permanent magnet (PM) flux reversal machine were investigated. The proposed design had concentrated, non-overlapping winding, which offered high average torque capability at a wide speed range. The no-load performances such as coil test analysis, three-phase flux linkage, flux distribution, back-EMF, and cogging torque, and load analysis, such as average torque versus current density, instantaneous torque, and average electromagnetic torque, were compared. The PM modular stator machine had high cogging torque, which created vibration and noise in the machine. Different cogging torque reduction techniques, such as notching, arc, flange and hybrid technique arc flange, arc notch, notch flange, and arc notch flange, were applied to reduce the cogging torque, improve average load torque, and reduce the induced voltage, harmonics, and torque ripples. The maximum cogging torque decreased by 87.66% and 82% when the arc notch flange and notch arc techniques were applied, respectively, and the minimum effect on cogging torque by the flange technique was 20.66%. Furthermore, the arc flange technique reduced the average torque by 66.72%. The maximum induced voltage was reduced by up to 12.83% using the notch arc technique. The hybrid technique of arc notch flange reduced the harmonics content in flux by 40% and enhanced electromagnetic performance. When applying the hybrid arc notch flange technique, torque ripples were reduced to 90.11%.

A comprehensive design approach for a three‐winding planar transformer

In this paper, a new three-winding planar transformer design with the integrated leakage inductor is proposed for a triple-active-bridge converter. It enables two output voltage levels: a high voltage (HV) output port and a low voltage (LV) output port. The primary and secondary windings are split unevenly in both side legs while the tertiary winding is connected in parallel. The unique winding configuration enables: (i) enhanced efficiency with low volume; and (ii) suppressed parasitic capacitances. Detailed transformer reluctance and loss models are developed in the design process. The core geometry is optimized using a reluctance-model-based mathematical computation. Moreover, comprehensive high-fidelity simulations are conducted to analyse the trade-offs among parasitic capacitances, losses, and inductances. The customized core and the non-overlapping winding boards are assembled, characterized, and tested under various power flow conditions.

Design and Analysis of Dual-Rotor Modular-Stator Hybrid-Excited Axial-Flux Permanent Magnet Vernier Machine

This paper proposes a new structure of the dual-rotor hybrid-excited axial-flux permanent magnet vernier machine (DR-HEAFPMVM) with the modular stator and the consequent-pole PM (CPM) rotor for low-speed, high torque density applications such as in-wheel electric vehicles. The tooth-wound non-overlapping armature windings and direct current (DC) excitation windings are, respectively, arranged in stator main-teeth and split-teeth to obtain the modulated and adjustable air-gap flux densities, resulting in high torque density and outstanding flux-weakening capability. First, the design considerations, operation principles, and air-gap flux density distributions of the proposed machine are elaborated based on the air-gap permeance function. Then, the influence of the pole ratios (PRs) and the DC excitation currents on the main electromagnetic performances of the DR-HEAFPMVM, such as the flux-weakening capability and back-electromotive force (back-EMF), on-load electromagnetic torque, loss distribution, and efficiencies, is investigated using the 3-D finite-element method (FEM). Results verify the feasibility of the flux adjustment of the DC excitation windings equipped in the split-tooth, and the design with a pole ratio of 8/1 tends to have higher torque density, higher machine efficiency, and considerable flux-weakening capability compared with the other two PRs.

Optimization and Improvement of Advanced Nonoverlapping Induction Machines for EVs/HEVs

This paper presents a comprehensive design optimization and performance improvement guidelines for induction machines (IMs) having advanced nonoverlapping windings (ANWs). The effectiveness of various optimization approaches, such as individual optimization and single- and multi-objective global optimization using the Genetic Algorithm (GA), has been studied. To minimize the potential drawbacks of high bar copper loss, high torque ripple, and low power at high speed due to high magnet-motive force (MMF) harmonics of nonoverlapping windings (NWs), two different performance improvement approaches have been utilized: (a) to redesign the rotor structure to reduce the parasitic effects such as torque ripple and additional bar copper losses due to air-gap flux density harmonics; (b) to increase the stack length to improve the torque at the constant-power region. It has been revealed that the proposed ANW IMs with bridges in their rotor openings, particularly with u-shaped bridges, show better performance in terms of torque ripple, bar copper loss, and bar current density. By using the proposed design method, an advanced IM (AIM) can achieve a 5.3% higher efficiency with ~34% shorter total axial length, compared to its conventional IM (CIM) counterpart with integer-slot distributed windings (ISDWs). A time-stepping 2-D finite element analysis (FEA) based nonlinear magnetic field solution program has been employed to perform all the parametric analyses, optimizations, and evaluate the optimal solutions and improved designs. Moreover, in order to show the reliability of the FEA predictions performed in this study, the FEA predictions of globally optimized CIM are validated by experimental measurements.

Optimization and Performance Evaluation of Non-Overlap Wound-Field Converter-Fed and Direct-Grid Wind Generators

Non-overlap winding technology continues to remain relevant in the design of wound-field machines as an alternative for high torque density permanent magnet machines. In this paper, the finite element analyses-optimisation of two variants of the non-overlap wound-field machines viz., wound-field flux switching machine (WF-FSM) and phase shifting wound rotor synchronous machine (WRSM), are compared, first in terms of their performance for large-scale converter-fed wind generator drives, then experimentally as sub-scaled converter-fed versus direct grid-connected wind generators, respectively. This study is unique because there are no prior attempts to design, optimize and analyse on these machines for medium-speed wind power generation, as well as experiment on sub-scale prototypes for direct-grid and converter-fed operation. All investigations are contemplated in the medium-speed wind generator drivetrain which provides a tradeoff for generator efficiency and size. From the global optimisation of both machines at large-scale power levels, the torque per mass of the WF-FSM is found to be 50 % lesser compared to the WRSM. This is due to approximate volume, with closely matched optimal split and aspect ratios. In terms of the sub-scaled experimentation, both generators can easily vary their generated output power to match with varying wind resource, but direct grid-connected WRSM generator yields better efficiency performance compared to the WF-FSM converter-fed operating mode, given that the generator terminal voltage of the former is highly regulated.