Non-overlapping Concentrated Windings Research Articles

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.

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.

Design and Analysis of Oil-Immersed Cooling Stator With Nonoverlapping Concentrated Winding for High-Power Ironless Stator Axial-Flux Permanent Magnet Machines

Ironless stator axial-flux permanent magnet (AFPM) machines provide many attractive electromagnetic performances such as high efficiency in high-frequency mode and strong short-term overload ability, which make them more competitive in flywheel energy storage applications. However, designing high-torque-density AFPM machines, particularly their ironless stators, is with significant challenges and needs great efforts. In this article, a high-strength oil-immersed cooling stator with nonoverlapping concentrated winding is proposed for high-power ironless stator AFPM machine applications. This article explains in detail the design, analysis, and manufacturing process of the proposed oil-immersed cooling stator. With the three-dimensional finite-element analysis (3-D FEA), a 9000-r/m/50-kW 12-slot/10-pole prototype for a flywheel energy storage system is successfully designed and developed using the proposed high-strength oil-immersed cooling ironless stator. The experimental test results demonstrate the effectiveness of the cooling design and mechanical strength.

Magnetic Noise Reduction of In-Wheel Permanent Magnet Synchronous Motors for Light-Duty Electric Vehicles

This paper presents study of a multi-slice subdomain model (MS-SDM) for persistent low-frequency sound, in a wheel hub-mounted permanent magnet synchronous motor (WHM-PMSM) with a fractional-slot non-overlapping concentrated winding for a light-duty, fully electric vehicle applications. While this type of winding provides numerous potential benefits, it has also the largest magnetomotive force (MMF) distortion factor, which leads to the electro-vibro-acoustics production, unless additional machine design considerations are carried out. To minimize the magnetic noise level radiated by the PMSM, a skewing technique is targeted with consideration of the natural frequencies under a variable-speed-range analysis. To ensure the impact of the minimization technique used, magnetic force harmonics, along with acoustic sonograms, is computed by MS-SDM and verified by 3D finite element analysis. On the basis of the studied models, we derived and experimentally verified the optimized model with 5 dBA reduction in A-weighted sound power level by due to the choice of skew angle. In addition, we investigated whether or not the skewing slice number can be of importance on the vibro-acoustic objectives in the studied WHM-PMSM.

Effect of Slot-Pole Combination on the Electromagnetic Performance of Ironless Stator AFPM Machine With Concentrated Windings

Due to the elimination of the magnetic core on the stator, the design of coils is more flexible and more sensitive to the number of rotor poles for ironless stator axial flux permanent magnet (AFPM) machine. The slot-pole combination is a vital aspect of optimization design for the improvement of torque and power density. This article is mainly aimed at investigating the influence of slot-pole combination on the comprehensive performance of ironless stator AFPM machine with non-overlapping concentrated windings. Firstly, the space utilization of coils and winding factor of non-overlapping concentrated winding are deduced in formula form to compare the output capacity. And the copper mass and utilization are analyzed with different numbers of slots and stator diameter. Then, field utilization ratio is defined and derived to analyze magnetic flux leakage of Halbach-array PM dual-rotor for different numbers of poles. The performance comparison of the optimized prototypes is carried out using three-dimensional finite element analysis (3-D FEA). The back-EMF, torque and winding loss are also highlighted. Finally, a 50 kW prototype with 12-slot and 10-pole is designed and manufactured for experimental validations. This paper provides a valuable reference to select the basic configuration for the ironless stator AFPM machine application.

Analysis of a Tooth-Coil Winding Permanent-Magnet Synchronous Machine With an Unequal Teeth Width

This paper presents an analysis of a permanent magnet synchronous machine (PMSM) with an unequal teeth width. The use of the concentrated nonoverlapping winding, also known as tooth-coil winding, has certain advantages. In addition, asymmetric features can be exploited by adopting this winding configuration to improve the machine performance. The procedure involves increasing the stator tooth width and, to the same extent, reducing the adjacent stator tooth width. In this paper, an analytical method was employed to predict and understand the back-EMF behavior, and a finite element analysis (FEA) was performed to verify the analytical method. Furthermore, a detailed study of the machine performance (electromagnetic torque, flux density, and losses) was carried out by the FEA. The machine was built and tested to validate the performance of the machine.

Comparative Study of Winding Configurations of a Five-Phase Flux-Switching PM Machine

This paper introduces a general method for determination of the most suitable winding configurations for five-phase flux-switching permanent magnet (FSPM) machines, associated with feasible stator/rotor-pole combinations. Consequently, the effect of winding configurations on the performance of a five-phase outer-rotor FSPM machine is thoroughly investigated, including non-overlapping concentrated windings (single-layer, double-layer, and multi-layer) as well as distributed winding. The electromagnetic characteristics in the low-speed region, the flux-weakening capability in the high-speed region, and the fault-tolerant capability under faulty situations are evaluated and compared in detail. This work shows that compared with the conventional single-layer or double-layer concentrated windings, the FSPM machine with multi-layer type winding exhibits lower torque ripple and losses. Meanwhile, the motor with distributed windings possesses higher torque density and larger inductance. Finally, a prototype is manufactured, and the analysis results are validated by experiments.

A Dynamic Multilayer Winding Thermal Model for Electrical Machines With Concentrated Windings

This paper presents a dynamic multilayer winding lumped-parameter thermal model dedicated to electrical machines with concentrated windings. The winding is layered into a series of circular rings by a novel layer strategy according to the winding temperature distribution obtained by a two-dimensional analytical slot winding thermal model. Accordingly, the layer number can be automatically and dynamically adjusted so as to accurately model the winding temperature distribution using the smallest layer number. Besides, the end-winding is also layered similarly to the slot-winding based on the thermal behavior of the nonoverlapping concentrated windings. The proposed winding model could accurately calculate the temperature distribution within the slot, including the winding maximum and average temperature. Experiments on a winding motorette and a water-cooled permanent magnet machines with concentrated winding intended for electric vehicles have been implemented to validate the proposed winding thermal model.

Double three-phase PMSM structures for fail operational control

This paper deals with permanent magnet synchronous motors (PMSM) structures. Especially their double three-phase arrangements are analysed in detail. Comparison of three different structures is treated. Non-overlapping concentrated winding is the first analysed structure. Distributed winding arrangement with interlaced sub-systems and also distributed winding arrangement with segregated sub-systems follows.The behaviour of all motor structures during normal operation is the same but the properties during faults are different. The motor behaviour during active short circuit (ASC) is discussed. ASC of whole motor and also partial ASC tests were performed. Current waveforms in different operating points are compared. Results show differences of individual structures with respect to operation during fault.

A Novel Fault Tolerant Machine With Integral Slot Non-Overlapping Concentrated Winding

A novel fault tolerant machine with integral slot non-overlapping concentrated winding (ISNCW) is proposed in this paper. With the distribution of phase windings in axial, the proposed machine realized excellent isolation capability between different phases. The performance comparisons between the proposed machine and the traditional integer slot overlapping winding (ISOW) machine are made by the analytical method and finite element analysis (FEA). Compared to the ISOW machine, the proposed machine has better performance in low speed high torque applications, and much better fault tolerant capability and flux weakening capability. Especially, the proposed machine appears excellent performance in limiting the short circuit current and preventing the irreversible demagnetization of permanent magnet under short-circuit fault. The phase independent structure makes the maintenance and replacement of the fault module convenient and saves the maintenance cost further.

Design and analysis of a three‐phase brushless flux switching generator for aircraft ground power units

This study proposes a new three-phase dual-rotor middle-stator brushless flux switching generator for 400Hz diesel-driven aircraft ground power units. For the proposed machine, both field and armature windings are hosted in the stator in such a way that not only fulfils brushless structure, but also realises the flux switching function. Moreover, both windings have non-overlapping concentrated windings to shorten the end-windings and reduce the copper losses. In the meantime, the rotor has only slots without any active parts. First, the machine detailed design is provided, and its performance is analysed using finite element method. Also, a selection topology of both stator and rotor pole arcs is carried out, targeting maximum generated electromotive force, minimum harmonic content, and minimum cogging torque. Then, a prototype is implemented and experimented to confirm the feasibility of the proposed machine.

On-Load Analysis of Saturated Surface Permanent Magnet Machines Using Conformal Mapping and Magnetic Equivalent Circuits

This paper presents an iterative method based on conformal mapping and magnetic equivalent circuits for on-load analysis of saturated surface permanent magnet machines with integer slot and fractional slot windings. Magnetic saturation is taken into account by defining additional point wires in the stator slots and interpolar region between the magnets. The added point wires create magnetomotive force equal to the magnetic voltage drops across iron core flux tubes that are calculated using magnetic equivalent circuit. An improved stator tooth model has been introduced that enables more accurate field calculations for tooth geometries with highly saturated tooth tips. The model also takes into account variation of permanent magnet magnetization due to external magnetic field. The proposed method has been implemented on a saturated 12 slot, 10 pole surface permanent magnet machine with nonoverlapping concentrated winding and shows a very good agreement with finite element calculations in terms of flux density, back electromotive force, and torque waveforms as well as $d$ - and $q$ -axis inductances, cross-saturation inductance, and permanent magnet flux linkage in both axes.

Analysis and Implementation of New Ironless Stator Axial-Flux Permanent Magnet Machine With Concentrated Nonoverlapping Windings

This paper presents the integrated design and analysis of a new axial-flux permanent magnet (AFPM) machine, which consists of an ironless stator with double-layer concentrated nonoverlapping windings and twin external rotors with Halbach-array PMs. A general sizing equation based on fundamental theory, easily adjustable for ironless stator AFPM machine with concentrated windings, is derived to obtain preliminary parameters. Then, by using three-dimensional (3-D) finite element analysis (FEA), the optimization of a primary machine is implemented. A precise and fast calculation method based on a 3-D FEA model is proposed to confirm the eddy-current loss for ironless stator winding. By making a tradeoff between dc current loss and eddy-current loss of Litz wire for winding, the efficiency is further improved for a high frequency operation. Despite using Halbach-array PMs, a certain thickness of a rotor yoke is recommended to increase air-gap flux density. Finally, a prototype machine is developed, experimented, and evaluated. The test results reveal the strong overload and heat dispersal capacity of the proposed stator ironless AFPM machine with the maximum efficiency of 98.5%. Measured performances of the manufactured prototype verify the validity of the proposed analysis method and FEA results.

Active Zone of Permanent Magnet Synchronous Machine with a Non-Overlapping Concentrated Winding

Abstract The research is devoted to the investigation of NdFeB permanent magnet (PM) based synchronous generators with non-overlapping concentrated windings. The rotor of such a generator has 10 pole pairs (PMs), which is dictated by the nominal voltage frequency (f=50 Hz) and the rotational speed (n=300 RPM). Comparison is made for four generators with three-phase winding coils and stator tooth numbers 18, 21, 24 and 27.

Nonlinear Analytical Model for a Multi-V-Shape IPM With Concentrated Winding

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.

A Stator-PM Consequent-Pole Vernier Machine With Hybrid Excitation and DC-Biased Sinusoidal Current

This paper proposes a novel hybrid excitation vernier permanent magnet machine (HE-VPM). The characteristics of the proposed machine are: 1) the PMs are embedded in the stator teeth, which is helpful for the heat dissipation; 2) the rotor is salient structure without PMs and windings, which ensures the reliability of high-speed operation; 3) the nonoverlapping concentrated winding shortens the end-connection, and improves the torque density, 4) only half of the stator teeth possess PMs, and the total amount of PMs are decreased; and 5) the dc current are injected to the armature coils, therefore, the exciting field can be adjusted flexibly. In this paper, the electromagnetic performance, including back electromotive force, torque, etc. are analyzed with finite element analysis. The results show that the proposed machine exhibits flexible field adjustment capability, which may be suitable for applications requiring wide speed range operation. Besides, it is found that, compared with the existing pure sinusoidal phase current, higher torque density can be obtained with dc-biased phase current under constant stator copper loss.

An Investigation of Zeroth-Order Radial Magnetic Forces in Low-Speed Surface-Mounted Permanent Magnet Machines

Zeroth mode of vibration is investigated in low-speed high-torque surface-mounted permanent magnet (PM) machines with non-overlapping concentrated windings. Magnetic field distribution in the air gap is computed using time-stepping finite-element analysis, and Maxwell stress tensor is then employed to calculate the radial force density. Based on the time variation of the mean value of the radial force density spatial distribution, the zeroth-order radial forces are studied. Simple structural equations are used to compare the stator deformations for the machines under investigation. Contribution of the zeroth mode to produce vibration is analyzed and compared with the lowest non-zero mode. The influence of pole and slot combinations and the effect of rectifier load are discussed. This paper is carried out to investigate whether or not the zeroth-order radial forces can be of importance in the presented surface-mounted PM machines that are not connected to pulsewidth modulation (PWM) converters.

Comparison of Flux-Switching PM Motors With Different Winding Configurations Using Magnetic Gearing Principle

In this paper, the magnetic gearing principle is extended to the flux-switching permanent magnet (FSPM) motor for its armature winding configuration design. First, the no-load flux density in motor air gap is qualitatively analytically calculated using the equivalent magnetic circuit method, so that the predominant space harmonic components (PSHCs) can be separated. Then, the slot vector graph can be drawn according to the pole-pair numbers and rotation directions of these PSHCs. Consequently, the armature winding configuration of a 12/10-pole FSPM motor is designed based on the slot vector graph using the conventional motor design method. In addition, two new 12/7-pole FSPM motors with the conventional non-overlapping concentrated and distributed winding are proposed, and the electromagnetic performances of the three motors are analyzed and compared. Finally, the analytical results are verified by the finite-element analysis and experimentation.

A Wound Field Switched Flux Machine With Field and Armature Windings Separately Wound in Double Stators

In this paper, a double stator (DS) wound field (WF) switched flux (SF) (DS-WFSF) machine is proposed. In the DS-WFSF machine, field and armature windings are separately placed in two different stators. Compared with the conventional WFSF machine with single stator, in which both field and armature windings are located, nonoverlapping concentrated windings and large slot areas can be obtained in the DS-WFSF machine. The proposed DS-WFSF machine exhibits >19% higher torque than the conventional WFSF machine, with both machines having the same space envelope and being globally optimized. The influence of leading design parameters, such as copper loss ratio between the field and armature windings, air-gap diameter, and rotor iron piece thickness and widths, on the average output torque is investigated for the DS-WFSF machines having 12/10, 12/11, 12/13, and 12/14 stator slots/rotor iron pieces. All the analyses are confirmed by both finite element and experimental results.

Effects of Loading and Slot Harmonic on Radial Magnetic Forces in Low-Speed Permanent Magnet Machine With Concentrated Windings

This paper investigates the effects of loading and slot harmonic on radial magnetic forces in a low-speed permanent magnet (PM) machine with non-overlapping concentrated windings. Vibration level of the PM machines with concentrated windings can be potentially higher compared with that of the traditional machines with distributed windings. It is mainly due to the presence of low-order spatial harmonics in radial force density distribution. In this paper, magnetic flux density distribution in the air-gap of a 120-slot/116-pole machine is computed using finite-element method. Maxwell’s stress tensor method is then employed to calculate radial and tangential forces in the air-gap. Flux density and radial and tangential force distributions are studied in different loading conditions and the effect of ${d}$ - and ${q}$ -axis currents are investigated. It is shown how the lowest mode of vibration is produced by different harmonic pairs in the flux density. It is found that ${d}$ -axis current significantly changes the amplitude of the lowest spatial harmonic of the radial force distribution and consequently the vibration behavior. The main reason is found to be the changes in the amplitude of the slot harmonic, which is heavily affected by loading. Experimental tests are carried out to compare the vibration level of a PM generator supplying resistive, inductive, and capacitive loads. There is a good agreement between simulations and experimental results.