Utility and Application of a Versatile Analytical Method for MMF Calculation in AC Machines

A versatile analytical method(VAM) for calculating the harmonic components of the magnetomotive force(MMF) generated by diverse armature windings in AC machines has been proposed, and the versatility of this method has been established in early literature. However, its practical applications and significance in advancing the analysis of AC machines need further elaboration. This paper aims to complement VAM by augmenting its theory, offering additional insights into its conclusions, as well as demonstrating its utility in assessing armature windings and its application of calculating torque for permanent magnet synchronous machines(PMSM). This work contributes to advancing the analysis of AC machines and underscores the potential for improved design and performance optimization.

Multi-Objective Optimization of High Torque Density Segmented PM Consequent Pole Flux Switching Machine with Flux Bridge

Due to double salient structure,Flux Switching Machines(FSMs)are preferred for brushless AC high speed applications.Permanent Magnet(PM)FSMs(PM-FSMs)are suited applicants where high torque density(Tden)and power density(Pden)are the utmost requisite.However conventional PM-FSMs utilizes excessive rare earth PM volume VPM,higher cogging torque Tcog,high torque ripples(Trip)and comparatively lower(Tden)and Pden due to flux leakage.To overcome the aforesaid demerits,a new high(Tden)Segmented PM Consequent Pole(CP)FSM(SPMCPFSM)with flux bridge and barrier is proposed which successfully reduces VPM by 46.52%and PM cost by 46.48%.Moreover,Multi-Objective Optimization(MOO)examines electromagnetic performance due to variation in geometric parameters for global optimum parameters with key metric such as flux linkage(Φpp),flux harmonics(ΦTHD)average torque(Tavg),Tcog,Trip,Tden,average power(Pavg)and Pden.Analysis reveals that MOO improveΦpp by 22.68%,boost Tavg by 11.41%,enhanced Pavg by 4.55%and increased Tden and Pden by 11.41%.Detailed electromagnetic performance comparison with existing state of the art shows that proposed SPMCPFSM offer Tavg maximum up to 88.8%,truncate Trip up to 24.8%,suppress Tcog up to 22.74%,and results 2.45 times Tden and Pden.

Torque Characteristics of High Torque Density Partitioned PM Consequent Pole Flux Switching Machines With Flux Barriers

Unique double salient structure of Permanent Magnet Flux Switching Machines(PMFSM)with both Concentrated Armature inding(CAW)and Permanent Magnet(PM)on stator attract researcher's interest for high speed brushless application when high torque density(T den)and power density(P den)are the primal requirements.However,despite of stator leakage flux,high rare-earth PM usage,PMFSM is subjected to slot effects due to presence of both PM and CAW in stator and partial saturation due to double salient structure which generates cogging torque(T cog),torque ripples(Trip)and lower average torque(T avg).To overcomne aforesaid demerits,this paper presents Partitioned PM(PPM)Consequent Pole Flux Switching Machine(PPM-CPFSM)with flux barriers to enhance flux mnodulation,curtail PM usage and diminish stator leakage flux which reduces slotting effects and partial saturation to ultimately reduces T cog and Trip In comparison with the existing state of the art,proposed PPM-CPFSM reduces 46.5390 of the total PM volumne and offer Tavg higher up to 88.8%,suppress Trip naximun up to 24.8%,diminish Tcog up to 22.74%and offer 2.45 times Tden and Pden.Furthermore,torque characteristics of proposed PPM-CPFSM is investigated utilizing space harmonics injection i.e.inverse cosine,inverse cosine with 3rd harmonics and rotor pole shaping techniques i.e.,ecce ntric circle,chanfering and notching.Detailed electromagnetic perfornance analysis reveals that harmonics injection suppressed Tcog maximun up to 83.5%,Trip up to 40.72%at the cost of 4.71%Tavg.Finally,rotor mnechanical stress analysis is utilized for rotor withstand capability and 3D-FEA based Coupled Elctromagnetic Thermal Analysis(CETA)for thermal behavior of the developed PPM CPFSM.CETA reveals that open space along PPM act as cooling duct that inprove heat dissipation.

Brushless Doubly-Fed Induction Machine as a Variable Frequency Transformer

VFT （variable frequency transformer） has been recently used as art alternative to HVDC （high voltage direct current） to control power flow between asynchronous networks. VFT consumes less reactive power than a back-to-back HVDC system, provides faster initial transient recovery, and has better natural damping capability. VFT is simply a DFIM （doubly-fed induction machine） where the machine torque controls the power flow from stator to rotor and vice versa. The main disadvantage of this VFT is the slip rings and brushes required for the rotor circuit, especially in bulk power transmission. The BDFM （brushless doubly-fed machine） with nested cage rotor machine is proved to be a comparable alternative to conventional DFIM in many applications with the advantage that all windings being in the stator frame with fixed output terminals. In this paper, the BDFM is used as a BVFT （brushless variable frequency transformer）. A prototype machine is designed and simulated to verify the system validity.

Overview of the Rectangular Wire Windings AC Electrical Machine

The rectangular wire winding AC electrical machine has drawn extensive attention due to their high slot fill factor,good heat dissipation,strong rigidity and short end-windings,which can be potential candidates for some traction application so as to enhance torque density,improve efficiency,decrease vibration and weaken noise,etc.In this paper,based on the complex process craft and the electromagnetic performance,a comprehensive and systematical overview on the rectangular wire windings AC electrical machine is introduced.According to the process craft,the different type of the rectangular wire windings,the different inserting direction of the rectangular wire windings and the insulation structure have been compared and analyzed.Furthermore,the detailed rectangular wire windings connection is researched and the general design guideline has been concluded.Especially,the performance of rectangular wire windings AC machine has been presented,with emphasis on the measure of improving the bigger AC copper losses at the high speed condition due to the distinguished proximity and skin effects.Finally,the future trend of the rectangular wire windings AC electrical machine is prospected.

Problems Related to Excitation Winding Surface Temperature Measurement of a Salient Pole Synchronous Generator in Rotation

This paper addresses some of the problems related to direct surface temperature measurement of a salient pole synchronous generator excitation winding in rotation. Excitation winding temperature is used for determining the dynamic limit in a PQ diagram. The paper also addresses procedures of improving the accuracy of surface temperature measurement using the contact DS 18B20 digital temperature probes. The paper also provides experimental results of direct temperature measurement of the excitation winding surface conducted in the salient pole synchronous generator in the rotation.

Analytical Analysis and Performance Characterization of Brushless Doubly Fed Induction Machines Based on General Air-gap Field Modulation Theory

Air-gap magnetic field modulation has been widely observed in electric machines.In this study,we present an analytical analysis and performance characterization of brushless doubly fed induction machines(BDFIMs)fed by two independent converters from the perspective of air-gap field modulation.The spiral-loop winding is studied in detail as an example to show the generalized workflow that can also be used to analyze other short-circuited rotor winding types,such as nested-loop and multiphase double-layer windings.Magnetic field conversion factors are introduced to characterize the modulation behavior of special rotor windings and facilitate their comparison in terms of cross-coupling capability,average torque,and harmonic content of the air-gap flux density waveforms.The stator magnetomotive force(MMF),rotor MMF,and resultant air-gap MMF are considered,based on which the closed-form inductance formulas are derived,and the torque equation is obtained along with the optimal current angle for maximum torque operation by using the virtual work principle.The design equations are then developed for the initial sizing and geometry scaling of the BDFIMs.Transient finite element analysis and experimental measurements are performed to validate the analysis.

Overview of Advanced Control Strategies for Electric Machines

Control strategies play a key role for operation of electric machines,which would directly affect the whole system performance.In fact,different control strategies have been executed and explored for electric machines,which bring great impacts to industrial development and human society.This paper investigates and discusses the advantages control strategies for electric machines,including the field oriented control(FOC),direct torque control(DTC),finite control set model predictive control(FCS-MPC),sensorless control,and fault tolerant control(FTC).The corresponding control principles,control targets,fundamental approaches,advanced approaches,methodologies,merits and shortcomings are revealed and analyzed in detail.

Optimal Rotor Poles and Structure for Design of Consequent Pole Permanent Magnet Flux Switching Machine

Permanent magnet flux switching machines(PMFSM)have attracted significant research interest and are considered as competent candidates when higher torque density is primary requirement.However,conventional PMFSMs uses excessive rare earth PM volumes which ultimately increases machine the machine weight and PM cost.Moreover,the PMs extended at the stator yoke results in stator leakage flux which degrades the performance.To suppress the leakage flux and diminish the PM volume,the consequent pole PMFSM(CPPMFSM)with flux bridges and barriers encompassing partitioned circumferential and radial magnetized PMs is proposed,thereby ensuring an alternate magnetic path for the working harmonics which improves the modulation effect and flux distribution.Moreover,the influence of the rotor pole number on seven different rotor structures namely,curved rotor,trapezoidal rotor,wide rotor tooth tip,wide rotor base width,rectangular segmented and eccentric rotors are investigated based on the electromagnetic performance and stress distribution.Finite element analysis(FEA)reveals that the 12S-13P CPPMFSM with a wider rotor base offers comparatively better electromagnetic performance.Compare to the conventional PMFSM,the proposed CPPMFSM reduces the PM volume which minimizes the overall machine cost and weight,suppresses the torque ripples by 16.49%,diminishes total harmonic distortion(THD)by 35.24%and decreases cogging torque by 32.88%.Furthermore,the torque and power density are enhanced by 7.028%and 7.025%respectively.

Spiral Vector Modeling of Brushless Doubly-fed Induction Machines with Short-circuited Rotor Windings

A unified spiral vector model is presented that can be used to assist the finite element method-based performance analysis of brushless doubly-fed induction machines with various short-circuited rotor windings.Specifically,magnet-free brushless doubly-fed induction machines working in doubly-fed or singly-fed synchronous mode are investigated.A dynamic model in spiral vector notation is developed,based on which the torque-angle and power-angle characteristics are derived.It is shown that the investigated brushless machines are equivalent to a traditional non-salient-pole synchronous machine with brushes.By introducing a conversion factor,they can also be analyzed with methods similar to the conventional phasor theory.A comparison is made between the brushless doubly-fed induction machine and non-salient-pole wound-field synchronous machine with brushes,revealing that the performance of the brushless machine degrades faster when the laminated core is saturated.A scaled-down prototype is tested to validate the effectiveness of the theoretical analysis.

Coupled Electromagnetic-thermal Analysis of Segmented PM Consequent Pole Flux Switching Machine

Compact stator structure of flux switching machines(FSMs)encompassing both permanent magnets(PMs)and armature winding slots(AWS)attract research interest whenever high power and density are the basic requirements.However,it also results in temperature rises owing to heat generation by electromagnetic power losses degrading the electromagnetic performance and affecting machine performance.In this study,a segmented permanent magnet(SPM)consequent pole FSM(SPM-CPFSM)is developed,which provides a stator cooling channel(duct)for improved heat dissipation to avoid demagnetization of PM as well as overheating.Furthermore,this study investigates detailed electromagnetic performance analysis and prediction of temperature variation in various machine parts owing to the heat generated by iron,copper,and magnet eddy current losses utilizing coupled electromagnetic-thermal analysis accounting for magnetic flux density variation.In comparison with the 2D analysis,the developed 3D coupled-field analysis more accurately predicts electromagnetic performance and temperature distribution.Analysis reveals that a cooling duct at the stator significantly assists in stator heat dissipation in the axial direction ensuring a safe operating condition of the PMs as well as machine parts to avoid overheating.

Magnetic Gearbox with an Electric Power Output Port and Fixed Speed Ratio for Wind Energy Applications

Mechanical gearboxes are typically employed with doubly-fed induction generatur-based wind turbines. The main drawback of this solution is the gearbox＇s reliability and maintenance. Using magnetic gearbox in conjunction with the doubly-fed induction generator is an emerging alternative being promoted by the research community which maintains the reduced size doubly-fed machine and overcomes the mechanical gearbox problems reported by field experience. This paper proposes a novel magnetic gearbox configuration in which a conventional planetary magnetic gearbox is equipped with n-phase coils fitted around the ferromagnetic pole-pieces to extract output electrical power. The turbine mechanical power is thus divided into mechanical power to drive the electrical generator and extra electrical power that can be diverted into a storage system to perform the power leveling function. The proposed configuration can also be used to freely modify the power-speed characteristic as seen by the electrical generator, a highly needed feature for grid frequency support.

New Technical Trends on Adjustable Speed AC Motor Drives

Adjustable speed AC Motor drives have been used extensively in modern industry and transportation which calls for electrical and mechanical energy conversion with wide output power range applications.Because of its modularity and scalability,the drive system can be extended to many different application areas.More recently,adjustable speed AC motor drive applications are spreading not only in industry applications,but also sky and the marine.In this paper,after summarizing the history of adjustable speed AC motor drives and applications,the main issues of AC drive technologies are reviewed and investigated in the paper.Technical issues of adjustable speed AC motor drives including its standardization are surveyed and analyzed for more advancement.Finally,the paper provides the latest technical trends on adjustable speed AC motor drives technologies,and discusses the development of high speed high power PM motor.