MMF Harmonics Research Articles

Analysis of Five-Phase Synchronous Reluctance Motor under Multi-Phase Faults

The model of a five-phase synchronous reluctance motor is presented, modelled to investigate the machine characteristic during multi-phase fault. The machine is modelled for a five phase supplied, with ACEBD winding configuration. The model considers the utilization of the third harmonics of the air-gap MMF as well the fundamental component, and a neglect of the third harmonics. These two models speed performance characteristics are monitored for multi-phase faults and their subsequence restorations. The fault pattern of losing 2𝜋5 phases from the first faulty before the 4𝜋5 radian phase and the losing of 4𝜋5 phase radian first before the 2𝜋5 radian phase. These phases were subsequently restored according to the considered fault patterns. The machine was then monitored on load and on no load using MATLAB/SIMULINK software for the analysis. The effect of the utilization of the third harmonic of the air-gap MMF is pronounced especially at fault and restorations.

Research on Winding MMF Harmonics of the PMSM with the Same Number of Poles and Slots

Research on Winding MMF Harmonics of the PMSM with the Same Number of Poles and Slots

A Versatile Analytical Method of Investigating MMF Harmonics of Armature Windings

A Versatile Analytical Method of Investigating MMF Harmonics of Armature Windings

The Effect of Unbalanced Excitation System on The MMF Analysis of The Six-Phase Winding.(Dept.E)

The effect of losing one-phase or more of the excitation system on the space MMF harmonics has been investigated for two types of six-phase stator windings ; by means of Goerge's vector diagram. The scope of this work covers the various changes in the resultant MMF waveforms that occur due to one-phase, or two-phase, or three-phase being opened. Consequently, an insight into avoiding the modes of operation which provide an objectional harmonic contents is given. The results obtained recommend to use the six-phase winding with phase spread , ẟ , eaual to 60 , in order to improve the overall reliability with one phase being opened ; the most common failures occurred.

Method of Making Combined Windings with a Set of Terminals that Create Both Co- and Counterrotating MMF Harmonics of Various Polarities

Method of Making Combined Windings with a Set of Terminals that Create Both Co- and Counterrotating MMF Harmonics of Various Polarities

Theory and Design of a Novel Multi-Layer Modular Modulation Winding

The modular winding structure can improve the production efficiency and facilitate the redundant design of electrical machine. Therefore, it is widely applied in industrial production. In this paper, one kind of multi-layer modular modulation winding (MLMMW) is proposed, in which each phase winding is composed of several sub-modules with adjustable turns. Based on MMF distribution principle, the design and optimization method of MLMMW with different slot/pole combinations are deduced in the form of mathematical expressions. By using the finite element method (FEM), electromagnetic parameters of the electrical machines with MLMMW are calculated and compared with that of electrical machines with traditional concentrated windings (TCW). The results show that the MLMMW can effectively reduce the MMF harmonics and improve the electromagnetic performance of electrical machine. The proposed winding structure is suitable for integral-slot and fractional-slot electrical machines with different slot/pole combinations, and it has good industrial application value.

Investigation of Doubly Salient Structure for Permanent Magnet Vernier Machines Using Flux Modulation Effects

Recently, the permanent magnet vernier machine (PMVM) is studied extensively because of its merits such as the high torque density. Similar to the magnetic gears, the PMVM operates on the principle of flux modulation. However, there is a distinct difference in between the two as unlike the magnetic gear, in case of PMVM, the winding MMF harmonics rotates with different speed as that of the fundamental. As a result, these harmonics are capable of making a working magnetic field by interacting with different permeance harmonics. Therefore, this paper aims to provide an analytical explanation of this whole process, which is helpful to understand the effect of the flux modulation on the output torque. Furthermore, using the analytical formulation, this work finds the optimal geometric parameters which maximize the working magnetic field and hence the torque. A detailed analysis of the PMVM with the doubly salient structure is studied and the performance is analyzed using the finite element method (FEM) and the experimental setup. The FEM and experimental results verify the maximum torque production by using the optimal geometric parameters in the PMVM modeling, obtained using the analytical formulation.

The main principles of the approach to the construction of combined windings with one set of terminations

The principle of the construction of an AC combined winding with one set of terminations with p1 and p2 polarities of the MMF is proposed. Equations of the MMF and the turn phase of the combined winding, which create accordant and counter-rotating harmonics of the MMF polarity p1 and p2, are obtained. The cases of construction of CO with accordant- and counter-rotating harmonics of MMF of different polarity are considered in detail. The main relation for the distribution of conductors in the slots is presented. The spatial pattern of accordant and counter-rotating harmonics of the MMF polarity p1=5 and p2=3 with equal angular frequencies are shown.

A High Speed PM Generator for an Organic Rankine Cycle System

This paper deals with the design guidelines of a high-speed permanent magnet generator used in an organic Rankine cycle system. These systems require an overall analysis that includes electromagnetic as well as mechanical aspects. Two important design aspects are taken into account. First, the design of the retaining sleeve is considered, since it influences both mechanical and magnetic aspects. Second, friction losses in the air gap and rotor losses due to current and MMF harmonics are considered. An in-depth design analysis is proposed and validated by experimental tests.

On the Influence of Increased Stator Leakage Inductance in Single-Tooth Wound Synchronous Reluctance Motors

This paper explores the leakage inductance of a single-tooth wound synchronous reluctance motor and its influence on motor performance. It is shown that the stator leakage inductance heavily influences the true saliency ratio in synchronous reluctance motors and a large stator leakage inductance has a serious detrimental impact on the operating power factor. It is also shown through analytical and finite element analysis analysis that synchronous reluctance motors with single-tooth windings suffer an inherent high stator leakage inductance that is dominated the air-gap harmonic leakage component, derived from the significant stator MMF harmonics experienced with this winding type. This explains for the first time the experimental results showing a low operating power factor compared to a distributed wound machine. Measurement of the stator leakage inductance is attempted on a prototyped machine and the standardized method is found to be lacking when single-tooth windings are employed.

Characteristics Analysis of PM Type Offshore Wind Power Generator with Dual Inverters according to Number of Per Pole Per Phase

This paper presents several characteristics of performance in dual 3-phase machine for offshore wind power generator according to number of per pole per phase, ‘q’. With the same rotor structure, the number of turn per coil is adjusted to the aim of same electrical loading. By using FEA, self-, mutual- and synchronous inductance are calculated. In addition, magnetic flux density, flux linkage, torque ripple, cogging torque, and demagnetization withstand are investigated. In case of q=1, the model can have large inductance, low mutual coupling between two phase coils, and good demagnetization withstand but it has large torque ripple and cogging. On the contrary, the generator with q=2 can have low torque ripple, cogging and relatively high average torque because of low MMF harmonics but it has high mutual coupling due to low inductance and bad demagnetization withstand.

Principle of Operation and Performance of a Synchronous Machine Employing a New Harmonic Excitation Scheme

This paper presents a new harmonic current excitation principle for a synchronous machine drive based on control of the spatial third harmonic MMF. Unlike existing harmonic excitation technologies, which utilize the third harmonic components of the rotor magnetic field, this brushless harmonic excitation principle is realized by injecting an ac single-phase current component or dc component into three-phase open stator windings thereby utilizing the resultant third harmonic spatial stator MMF component. This additional component generates either a stationary or time pulsating magnetic field which will induce voltages in a specially designed rotor winding. Through rectification, the induced voltage is used to supply dc current to the rotor excitation winding. To verify the aforementioned principle, theoretical analyses, magnetic field calculations by finite-element analysis and experiments with a 1.0-kW prototype machine have been performed and key influential factors have been investigated. The test results are shown to be consistent with the theoretical analysis, which validates the correctness of the theory.

Calculation improvement of no-load stray losses in induction motors with experimental validation

On the basis of the known fact that all air gap main flux density variations are enclosed by permeance slot harmonics, only one component of stray losses in rotor (stator) iron is considered in the new classification, instead of 2 components: rotor (stator) pulsation iron losses, and rotor (stator) surface iron losses. No-load rotor cage (high-frequency) stray losses are usually calculated. No-load stray losses are caused by the existence of space harmonics: the air-gap slot permeance harmonics and the harmonics produced by no-load MMF harmonics. The second result is the proof that the corresponding components of stray losses can be calculated separately for the mentioned kind of harmonics. Determination of the depth of flux penetration and calculations of high frequency iron losses are improved. On the basis of experimental validation, it is proved that the new classification of no-load stray losses and the proposed method for the calculation of the total value is sufficiently accurate.

Harmonic Winding Factors and MMF Analysis for Five-phase Fractional-slot Concentrated Winding PMSM

To enhance torque density by harmonic current injection, optimal slot/pole combinations for five-phase permanent magnet synchronous motors (PMSM) with fractional-slot concentrated windings (FSCW) are chosen. The synchronous and the third harmonic winding factors are calculated for a series of slot/pole combinations. Two five-phase PMSM, with general FSCW (GFSCW) and modular stator FSCW (MFSCW), are analyzed and compared in detail, including the stator structures, star of slots diagrams, and MMF harmonic analysis based on the winding function theory. The analytical results are verified by finite element method, the torque characteristics and phase back-EMF are also taken into considerations. Results show that the MFSCW PMSM can produce higher average torque, while characterized by more MMF harmonic contents and larger ripple torque.

Influence of Winding Structure and the Effect of MMF Harmonics to the Spindle Motor Performance for Ultrahigh TPI HDD

The technologies for maintaining high recording density to suppress mechanical vibration and media flutter for ultrahigh TPI hard disk drive (HDD) require advance spindle motor design and technology against the traditional norms. To realize multimagnetic poles with limited stator slots, spindle motors generally use concentrated windings which offer small end winding and simple structure suitable for mass production. There is a variety of ways to construct a motor with different winding structures based on different pole/slot combinations. Winding structures directly affect the producing of motor back-emf and torque which determine motor capacity, reliability and efficiency. In this work, detailed analysis is carried out to identify the optimal winding structures of the high speed spindle motor and analyze their effect on the motor performances by using magneto-motive force harmonics analysis and electromagnetic magnetic field analysis. Results are useful in preliminary and final optimal designs of the high speed spindle motors.

Magnet Software Based Fault Analysis of Induction Motor Using Finite Element Analysis

Induction motor is one of the most commonly preferred motors used in the industry due to its long life & rugged construction. Faults occurring in an induction motor can significantly affect the performance of the motor and the drive which is running it. This project aims to study & analyze the faults which can occur internally in an induction motor .To implement fault analysis first the machine is modeled using MAGNET software. The motor is studied under healthy conditions. Subsequently faults are introduced & fault analysis is carried out. In the model of induction rotor bars are broken and the study is mostly based on magnetic field analysis of the motor under healthy conditions & under faulty conditions. The variation of starting torque with respect to increasing number of broken rotor bars is studied and a graph was plotted to show the variation. The stator winding currents produce a magnetic field that rotates in a counterclockwise direction. The changing magnetic field of the stator induces electromotive force in the rotor cage winding. The induced emf causes current to flow and magneto motive force in the rotor windings. In turn the rotor mmfs produce a magnetic flux pattern which also rotates in the air gap at the same speed as the stator winding field. Induction motors are the most commonly used prime movers in industrial applications. They are best suited for constant speed applications. Speed control can also be done with the help of power converter circuits. The 3-phase squirrel cage induction motor is the workforce of the industry as it is rugged & reliable. The interaction between the primary field and secondary currents produces torque from zero rotor speed onwards. The rotor speed at which the rotor currents are zero is called ideal no-load or synchronous speed. The rotor windings may be multiphase (wound motors) or made of bars short-circuited by end rings (cage rotors). All primary and secondary windings are placed in the uniform slots stamped into thin silicon steel sheets called laminations. The induction machine has a rather uniform air gap of 0.2 to 3mm.The secondary windings may be short circuited or connected to an external impedance or to a power source of variable voltage and frequency. Induction motors are the most commonly used prime movers in industrial applications. They are best suited for constant speed applications. Speed control can also be done with the help of power converter circuits. The 3-phase squirrel cage induction motor is the workforce of the industry as it is rugged & reliable. Electrical related faults are frequently occurring faults in three-phase induction machine which will produce more heat on both stator and rotor winding. This leads to the reduction the life time of induction machine. Stator winding fault in Induction Motors can be detected using Unknown Input Observer (UIO) & Extended Kalman Filter methods. They are used for speed estimation and fault detection methods respectively(1).Using analysis of permeance and MMF harmonics, frequency of air gap flux density harmonics which occur due to irregularities are calculated. It helps in detecting faulty ball bearing conditions (2). A procedure for electromagnetic design of three phase Induction Motor is discussed. This procedure is based on self-consistent equations. The electrical and magnetic properties are imposed by the user but the geometric dimensions are automatically calculated (3).The choice between Copper rotor bars and fabricated Aluminum rotor bars is discussed and debated. The fundamentals of rotor construction and basic information on how the Induction Motor works are discussed (10). The new IEC standard which defines the stator winding insulation requirement when the Induction Motor operates with Adjustable frequency drives (AFDs) is discussed. The

Air-Gap Flux Density Characteristics of Salient Pole Synchronous Permanent-Magnet Machines

The detailed knowledge of the field distribution in the air gap is of main importance for predicting and optimizing the performance of electric machines. In this paper, the air-gap flux density of a salient pole permanent-magnet (PM) synchronous machines is determined and investigated using a new analytical model. The stator slotting and rotor saliency effect, and also the air-gap MMF harmonics are considered. Different no-load and under load simulations are performed to show the permeance effect (rotor saliency and stator slotting) on the air-gap flux density characteristics of this type of machine. The simulations results show that as results of the permeance harmonics additional harmonics are induced on the air-gap flux density and these harmonics are very sensitive on the rotor pole shape parameters. Furthermore, the time domain analysis shows also that the permeance harmonics leads to the fluctuation of the resulting air-gap flux density harmonics with the time.

A Novel VSI- and CSI-Fed Dual Stator Induction Motor Drive Topology for Medium-Voltage Drive Applications

A new configuration is proposed for high-power induction motor drives. The induction machine is provided with two three-phase stator windings with their axes in line. One winding is designed for higher voltage and is meant to handle the main (active) power. The second winding is designed for lower voltage and is meant to carry the excitation (reactive) power. The excitation winding is powered by an insulated-gate-bipolar-transistor-based voltage source inverter with an output filter. The power winding is fed by a load-commutated current source inverter. The commutation of thyristors in the load-commutated inverter (LCI) is achieved by injecting the required leading reactive power from the excitation inverter. The MMF harmonics due to the LCI current are also cancelled out by injecting a suitable compensating component from the excitation inverter, so that the electromagnetic torque of the machine is smooth. Results from a prototype drive are presented to demonstrate the concept.

Fractional slot permanent magnet brushless machines and drives for electric and hybrid propulsion systems

PurposeFractional slot permanent magnet (PM) brushless machines having concentrated non‐overlapping windings have been the subject of research over last few years. They have already been employed in the commercial hybrid electric vehicles (HEVs) due to high‐torque density, high efficiency, low‐torque ripple, good flux‐weakening and fault‐tolerance performance. The purpose of this paper is to overview recent development and research challenges in such machines in terms of various structural and design features for electric vehicle (EV)/HEV applications.Design/methodology/approachIn the paper, fractional slot PM brushless machines are overviewed according to the following main and sub‐topics: first, machine topologies: slot and pole number combinations, all and alternate teeth wound (double‐ and single‐layer windings), unequal tooth structure, modular stator, interior magnet rotor; second, machine parameters and control performance: winding inductances, flux‐weakening capability, fault‐tolerant performance; and third, parasitic effects: cogging torque, iron loss, rotor eddy current loss, unbalanced magnetic force, acoustic noise and vibration.FindingsMany fractional slot PM machine topologies exist. Owing to rich mmf harmonics, fractional slot PM brushless machines exhibit relatively high rotor eddy current loss, potentially high unbalanced magnetic force and acoustic noise and vibration, while the reluctance torque component is relatively low or even negligible when an interior PM rotor is employed.Originality/valueThis is the first overview paper which systematically reviews the recent development and research challenges in fractional‐slot PM machines. It summarizes their various structural and design features for EV/HEV applications.

Core Losses and Torque Ripple in IPM Machines: Dedicated Modeling and Design Tradeoff

The proper combination of stator and rotor slot numbers is pursued in the design of interior permanent-magnet (IPM) motors with wide constant-power speed range. At high speed, in the flux-weakening region, the arising of stator and rotor iron losses due to magnetomotive-force (MMF) spatial harmonics limits the IPM motor performance. Torque ripple is another problem for this kind of machines, both at low and high speed. The numbers of stator slots and rotor equivalent slots have a major impact on both the loss and ripple aspects. A simplified model is proposed here in order to evaluate both problems with a general approach and point out the possible design tradeoff. With respect to previous models in the literature, both stator and rotor losses are included, and a more comprehensive approach is followed in the description of the rotor MMF harmonics. The model's effectiveness is tested through finite element analysis simulations and some experimental results. The proposed approach is useful for the selection of the IPM machine structure according to the specific requirements of the application.