Contents List of figures.
3 1.0 Introduction. 4 2.0 Aims and objectives.
7 3.0 Literature review.. 8 4.0 Project management (Gant chart) 11 5.0 Progress of the work. 13 5.
1 Design of permanent magnet machine. 13 5.3 Finite element analysis.
14 6.0 Summary and conclusion. 16 References. 17 Appendices. 18 Appendix 1- Figures and drawings. 18 List of figuresFigure 1: Airgap windings in axial flux permanent magnet 18Figure 2:Permanent magnet rotor with multipoles. 18Figure 3:Modular assembly of multipole permanent magnet rotor. 19Figure 4:Initial CAD model of permanent magnet machine.
19 1.0 Introduction The global consumption of energy in the form of electricity inthe year 2016 as reported by the united states government agency wasapproximately 22000TWh (Yearbook.enerdata.
net, 2018). The growth of electricityconsumption is rapid, and it is predicted to reach 30116 TWh in the year 2030. Thesedays one of the most important goals for international energy policy is toprevent climatic change, i.e. reduce global worming effect. Therefore, it ispredicted that carbon dioxide emission will be little as compared to presentscenario. To achieve maximum electricity production to cater ever growingrequirement of electricity with reduced carbon footprint it is necessary forall the countries to adopt efficient renewable energy sources such as solar andwind, without the help of renewable natural energy sources to produceelectricity it is impossible to reduce ambitious carbon foot print goalglobally (Aleksashkinand Mikkola, 2008). Generators and motors, which areessentially electromechanical energy conversion devices play a crucial role inenergy production and consumption.
To reduce carbon emission that adhere tointernational policies but also meet the demands of the ever-growing energymarket its necessary to focus on renewable energy and to enhance theefficiencies of electromechanical energy conversion devices such as generatorsor motors. One of the efficient solution can be permanent magnet technology forelectromechanical power consumption. It is possible to create competitivedistributed energy technology with new conversion apparatus due tosophistication of available energy conversion technologies with permanentmagnets.
Direct driven windmill generators is one example of such developmentas it can be enhanced by utilizing the benefits of permanent magnet technology.Industrial use of the permanentmagnet started since the invention of very first permanent magnet at thebeginning of the 20th century. For electric machines such asrotating as well as linear machines permanent magnet motors are used which isthe well-known application. Permanent magnet motors are in use for decades invarious applications due to its low initial cost and simple structuralrequirements. The applications of permanent magnet machines have been exploitedrecently for more challenging tasks due to improvement of permanent magnetcharacteristics and low cost.
Therefore, it is found that most modernapplications of permanent magnets are efficient as well cost competitive (Aleksashkinand Mikkola, 2008).This project work is an effort todesign the permanent magnet machine for the application of wind turbine. Theneed and benefits of using permanent magnet machines are briefly described inearlier paragraphs. One of the benefits mentioned such as reducing global warmingor carbon emission or basically making earth greener and getting it rid ofpollutants is one of the main motivations for me to select this topic for myproject.
The primary motivation for the project work is the needed initiativeto reduce the carbon foot print in the field of electricity production, whichcan be achieved by utilising renewable natural resources considering present scenario.The permanent magnet machines are the possible solution due to various benefitsoffered by them with competitive cost. 2.0 Aims and objectivesAim of this project work is todesign a permanent magnet motor for application in wind turbine. To achievethis aim successfully following objectives have been laid down,- Tocarry extensive research, online as well as offline on permanent magnetmotors/generators and wind turbine- Toselect a wind turbine to understand the capacity that will help the design- Tostudy and design different components of the permanent magnet of the motorbased on requirement of wind turbine, this objective need extensive study as itwill have required to design or select the power density/torque, efficiency, operatingspeed etc- Finiteelement analysis of the design to find the suitability of the design for windturbine under various conditionsIt is necessary to note that, awind turbine is a huge device, therefore actual assembling and testing of thepermanent magnetic machine will be costly at academic level, therefore, theefforts will be taken to scale down the wind turbine to a level whichassembling of prototype and testing of the permanent magnetic machine will becheap in terms of cost. 3.0 Literature reviewAll electromagnetics energyconversion devices which incorporates permanent magnet technology are describedby the term ‘permanent magnet machine’. A single or multiple permanent magnetare used for magnetic excitation.
Variety of configurations could be found inthe energy converter that employs permanent magnet technology, several examplesare, generator, motor, stepper motor, alternator, actuator, linear motor,control motor, transducer, brush less DC motor, tachometer and many more. Thestator of the motor is like the stator of the multiphase AC motor. The newcomponent incorporated in the permanent magnet motor is rotor, the rotor iscomplete contrast to that of conventional rotors.
In this application, rotorrelies of magnetic excitation unlike excitation by electric current in thewinding of multiphase AC motors. To achieve the higher efficiency for thedesired load characteristics, high efficiency, high power factor as well asperformance, it is necessary to optimise the configuration of the rotor,mechanical design and electromagnetic rotor and the design of theelectromagnetic stator (Rizk et al, 2000). The direct drive wind turbineapplication requires a machine with high power density, high power torque, highefficiency with low design operating speed. The primary reason to use directdrive permanent magnet machine is that the machine has an ability to reduce thecost of converting wind power to mechanical power simply by eliminating thenecessity of step up gear box. The speed increasing gear box is usually incorporatedin wind mill to amplify the small rpm of the wind rotor to higher rpm toproduce electricity. The cost associated for the operation as well asmaintenance of direct drive permanent magnet machine is very low as compared togear coupled machines. The role of low speed, high power direct drive electricmachines are extensively limited to special applications such as largehydroelectric generators therefore they are not commonly used in the industry.Therefore, low speed and high torque motors need reliable evaluation andexperimentation to analyse their suitability for the wind turbine applicationas a direct drive device.
Such suitable application could be revolutionary dueits high performance, low cost and simple structural requirements. (Baywaters etal, 2005)Wind energy can make significant contribution to the electricity utilitynetwork due to it being an inexpensive renewable energy source. However, twoissues need to be addressed first relating to the construction of the windpower generator. The first one being the instability of the wind speed and thesecond one, the rotating speed of the wind turbine which is low due to thelarge diameter of the rotor blades. The technologies have been developed toestimate the variable speed constant frequency to counter the instability ofthe wind speed. The later issue was addressed by using conventional solution ofgear box to increase the speed which helps to reduce the size of generators.Using gear box though comes with its cons such as more noise and vibrations,high losses in gear drive due to gear box being a mechanical device, the needof constant lubrication and maintenance of gear box. Gear box’s cost is also high.
Direct driven variable speedpermanent magnet machines have various advantages such as such competitive costand possibility to eliminate the gear box from wind turbine structure. Energycapture is increased in such application by using variable speed. The removalof gearbox weight also leads to reduction of wind mill losses which results inenhanced system efficiency. Frequency ofperiodic maintenance is also reduced thus reducing maintenance cost.Although, large numbers of polesare required to construct a generator due to low rotational speed; it isnecessary for the generator that it should be efficient naturally with acompetitive cost. To supply power to the grid, frequency converter is requireddue to the variable speed scheme.
According to (Fengxiang et al, 2005) smallpole pitch can be achieved by incorporating large pole numbers with permanentmagnets. A simple and effective generator construction is shown in figure 1 ofappendix 1 in the form of disc type axial flux configuration. The stator in thefigure shown is a toroidal wound accommodating rectangular coils which forms anair gap winding. Permanent magnets are attached to the rotor disc located onboth side of stator.According to (Spooner et al, 1996), the assembly of the permanentmagnet machine is the crucial problem during its construction. No strong forcesare present at the time of assembly as the assembly of the magnet is carriedout individually and iron parts are already located in the position in themodern assembly practice of permanent magnet machines.
To reduce the assembly problemsof PM generators the modular construction is proposed by to (Spooner et al,1996). The paper presented by to (Spooner et al, 1996) says that, for the largegrid connected wind turbines, direct coupled, permanent magnet, synchronouswith radial field and multipole machines can be used. The power rating could bebetween 100 kW to 1 MW and pole numbers could be between 100 to 300. Employingmodular constructions help to reduce need of detail design, number of tools anddrawings.
The modular assembly practice can be utilised in vast ranges ofmachines. The standard ferrite magnet blocks are used in the rotor module,whereas the stator module is formed by single rectangular coil embedded insimple E-cores. The assembly of the magnetised parts can be arranged easilywhich improves the efficiency of the machine with low reluctance. The multipolepermanent magnet is shown in figure 2 of appendix 1 whereas modular arrangementof magnet is shown in figure 3 of appendix 1 which help to visualise thedifference. 4.0 Project management (Gant chart) The above is the zoomed out full screencapture of Smartsheet, a software I used to make my Gantt chart.
Below is thetable of content that was used for Gannt chart and the images showing the full Gantt chart. Selecting a project 10/10/17 10/14/17 5d Completed Background reading for the project 10/16/17 10/22/17 7d Completed Project brief 10/23/17 10/23/17 1d Completed Literature review 10/23/17 11/06/17 15d Completed Submission of ethics approval 11/13/17 11/13/17 1d In Progress Gnat chart/timeplan preparation 10/21/17 10/21/17 1d Completed Preliminary analysis of the work 11/13/17 11/27/17 15d Completed Understanding design requirements of Permanent magnet machines 11/20/17 12/04/17 15d Completed Familirising with FEA concept and University FEA software 12/04/17 12/20/17 17d In Progress Progress report writing and referencing 12/20/17 01/08/18 20d Completed Submission of progress report 01/15/18 01/15/18 1d Completed Design of permanent magnet machine 01/24/18 02/12/18 20d Not Started Simulation of design in FEA software and its evaluation 02/12/18 03/05/18 22d Not Started Critically analyzing FEA results 03/05/18 03/19/18 15d Not Started Completing the final report 03/20/18 04/23/18 35d Not Started Submission of report 04/29/18 04/29/18 1d Not Started Viva 05/11/18 05/11/18 1d Not Started The above 3 imagescombined horizontally make the full length Gannt chart. The image below isthe full Gantt chart represented in a zoomed-out way to fit it on single page. 5.0 Progress of the workThe progress of the work shownhere is divided in to two parts,1. Designof permanent magnet machine2.
Finiteelement analysis of the design5.1 Design of permanent magnetmachineDuring the study of permanentmagnet machine, various important design parameters were studied which isincorporated in the design of the permanent magnet machine, Ratedpower of the machine- Velocityof the wind speed and speed ration of driving shaft governs the rated output ofthe generator. For this project work, minimum wind speed of 4 km/hour isconsidered, the rpm produced by the shaft and output of the generator withsingle phase connection will be calculated theoretically and evaluated duringFEA analysis of the design. Numberof phases and poles- Numberof stator poles decide the number of phases in the machine. The thumb rule isthe number of stator poles are twice than number of phases.
It has been foundthat during research, torque ripple increases with small numbers of phases whereascogging torque reduces with large pole numbers. Considering these constraints,three-phase machine is selected. By using electrical engineering handbook by(Chen, 2004), 24 number of stator poles are selected to reduce the torqueripples. The rotor pole is selected considering the relation between the rotorand stator.
Framesize- Dimension for allelectrical machines are freeze by International Electro-Technical Council knownas IEC, which comply the ISO regulations. The stator and rotor ratio selectedat this moment is 1:16 but it may change during designing of the Permanentmagnet motor depending upon the need. The structure size is yet to be finalizedalthough preliminary selection of the ratio fixes the frame structure.Airgap- The probability of coggingtorque increases due to use of permanent magnets therefore to reduce the sameand to increase the flux density air gap will be limited to a range of 0.
5 to1.0 mm.Machinespecification- design of permanent magnetmachine is ongoing, and all the parameters are not fixed yet. Therefore a tentative specification of permanent magnetrotor is given below based on selection through engineering handbook and ratio,just a note, below specification might change depending on the designrequirements,Table1: Initial specification of permanent magnetmachine No Parameters Value 1 Rating 3000 W 2 Stator poles 24 3 Magnet poles 8 4 Phases 3 5 Poles per phase 8 6 Length of air gap 0.
5 to 1.0 mm 7 Stator diameter 0.16 m 8 Rotor diameter 0.1 m 9 Length of magnet 0.015 m 10 Length of back iron 0.016 m Based on initial specification ofpermanent magnet machine, initial CAD model is generated which shown in figure4 of appendix 1. 5.
3 Finite element analysis The design of PM machines will bevalidated in FEA (Finite Element Analysis) software available in the universitysuch as Hyperworks 2017.2 or any other used in the university. The FEA softwareis a powerful tool which help to analyse the design and allows necessarychanges before actual production and assembly. Various scenarios can besimulated to check the performance of the PM machine. In this project work, FEA will beused to check the designed structure of the machine, excitation of the rotor,material properties and torque produced due to different rotor position as wellas wind current. The step by step approach will be used to find solution ofcontinuum problem during FEA analysis; for example, elements are created bydividing the continuum region by using different shapes of elements.
It may bepossible that different shapes of element produce similar solution for thecontinuum. It has been found during familiarization of software that it isquickly possible to express material properties, constraints and excitationalthough it is comparatively difficult to express. Other important parameterswill be calculated by using solution of system equation, such as, electromagneticproblems, Components of magnetic flux density are nodal unknowns. By usingthese components torque, induction and several other electromagnetic parameterswill be calculated and compared with the design one.Following assumptions are made todetermine distribution of magnetic field inside the machine.
These assumptionsare primary and may vary during actual simulation of the design,1. Sincethe magnetic field outside the status stamping is almost negligible hence themagnetic vector potential line of outer periphery of the status stamping istreated as zero2. Hysteresiseffects are neglected as magnetic material is isotropic for stator and rotorstampings3. Componentsof Z- directions are Current density (J) and magnetic vector potential (A)4. Distributionof magnetic field along the generator’s axial direction inside the generator isconstant5. Endeffects are considered to be zero 6.0 Summary and conclusionThe progress report includesbrief overview of permanent magnet machine with its application in windturbine, benefits of the same if used in the wind turbines followed by aim,objectives and literature review with primarily emphasis on construction,assembly and capacity of permanent magnet. Project management section showsgnat chart in detail along with its completion status.
Progress report on theother hand shows the completed work so far in design part as well as futureconsiderations and assumptions for FEA.Initial design specification forthe PM machine is completed, along with initial CAD drawing for the same.Detail design procedure is in process and it will be completed by end of week8. Study of FEA software by using similar case studies have been carried out.Once the final design of the PM machine is completed then CAD modelling and FEAsimulation will commence which is around start of week 9. Any alterationrequired in the design will be carried out considering the results of FEA.
Comparison of initial and final design along with FEA justification will beprovided. In conclusion permanent magnetmotor when used for wind power reduces carbon emission as wind energy isrenewable energy and this model of work can be an efficient solution. Also withdeveloping technologies this method might also become more efficient andcheaper. All in all my project is alittle behind due to some uncertainties about some design aspects due to my illhealth during this semester but I will catch up and complete it on time in thecoming semester. ReferencesAleksashkin, A.
and Mikkola, A.(2008). Literature review on permanent magnet generators design and dynamicbehaviour. Lappeenranta: Lappeenranta University of Technology, p.
1-11.Bywaters, G., John, V., Lynch,J., Mattila, P., Norton, G.
, Stowell, J., Salata, M., Labath, O.
, Chertok A.,Hablanian, D., April 12, 2001 to January 31, 2005, “Northern Power Systems WindPACT Drive Train Alternative Design Study Report”.Karthikeyan, V and Thulasiyammal,C. (2016). Design of Permanent Magnet Generator for Direct Driven Vertical AxisWind Turbine.
International journal of innovative technology and research. 4(2), pp 2794-2795.Rizk, J.
, Nagrial, M., 2000.”Design of permanent-magnet generators for wind turbines”, Power Electronicsand Motion Control Conference, Proceedings, IPEMC 2000, The ThirdInternational, 1, p. 208-212.Spooner, E., Williamson, A.
C.,Catto, G., 1996, “Modular design of permanent-magnet generators for windturbines”, Electric Power Applications, 143(5), pp.
388-395.Wang Fengxiang, Bai Jianlong, HouQingming, Pan Jian, 2005, “Design features of low speed permanent magnetgenerator direct driven by wind turbine”, Electrical Machines and Systems, 2005.ICEMS 2005. Proceedings of the Eighth International Conference, 2, pp.1017-1020.Yearbook.enerdata.
net. (2018).World Power consumption | Electricity consumption | Enerdata. onlineAvailable at:https://yearbook.
enerdata.net/electricity/electricity-domestic-consumption-data.htmlAccessed 6 Jan. 2018. Appendices Appendix 1- Figures and drawingsFigure1: Airgap windings in axial flux permanent magnet (Fengxiang et al, 2005)Figure2: Permanentmagnet rotor with multipoles (Spooner et al, 1996)Figure3: Modularassembly of multipole permanent magnet rotor (Spooner et al, 1996) Figure 4: Initial CAD model ofpermanent magnet machine