DOCSLIB.ORG

Modelling, Analysis, and Control Aspects of a Rotating Power Electronic Brushless Doubly-Fed Induction Generator

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Modelling, Analysis, and Control Aspects of a Rotating Power Electronic Brushless Doubly-Fed Induction Generator Modelling, Analysis, and Control Aspects of a Rotating Power Electronic Brushless Doubly-Fed Induction Generator NAVEED UR REHMAN MALIK Doctoral Thesis in Electrical Machines and Drives Stockholm, Sweden 2015 Laboratory of Electrical Energy Conversion (E2C), TRITA-EE 2015:63 KTH Royal Institute of Technology, ISSN 1653-5146 Teknikringen 33, 100 44 Stockholm, ISBN 978-91-7595-691-6 SWEDEN Akademisk avhandling som med tillstånd av Kungl Tekniska högskolan framläg- ges till offentlig granskning för avläggande av teknologie doktorsexamen i månda- gen den 19 Oktober 2015 klockan 10:00 i Sal F3, Kungliga Tekniska Högskolan, Lindstedtsvägen 26, Stockholm. © Naveed ur Rehman Malik, September 2015 Tryck: Universitetsservice US AB iii Abstract This thesis deals with the modeling, analysis and control of a novel brush- less generator for wind power application. The generator is named as rotat- ing power electronic brushless doubly-fed induction machine/generator (RPE- BDFIM/G). A great advantage of the RPE-BDFIG is that the slip power recovery is realized in a brushless manner. This is achieved by introducing an addi- tional machine termed as exciter together with the rotating power electronic converters, which are mounted on the shaft of a DFIG. It is shown that the exciter recovers the slip power in a mechanical manner, and delivers it back to the grid. As a result, slip rings and carbon brushes can be eliminated, increasing the robustness of the system, and reducing the maintenance costs and down-time of the turbine. To begin with, the dynamic model of the RPE-BDFIG is developed and analyzed. Using the dynamic model, the working principle of the generator is understood and its operation explained. The analysis is carried out at speeds, ±20% around the synchronous speed of the generator. Moreover, the dynamics of the generator due to external load-torque disturbances are inves- tigated. Additionally, the steady-state model is also derived and analyzed for the machine, when operating in motor mode. As a next step, the closed-loop control of the generator is considered in detail. The power and speed control of the two machines of the generator and the dc-link voltage control is designed using internal model control (IMC) principles. It is found that it is possible to maintain the stability of the generator against load-torque disturbances from the turbine and the exciter, at the same time maintain a constant dc-link voltage of the rotor converter. The closed-loop control is also implemented and the operation of the generator with the control theory is confirmed through experiments. In the third part of the thesis, the impact of grid faults on the behaviour of the generator is investigated. The operation of the generator and its re- sponse is studied during symmetrical and unsymmetrical faults. An approach to successful ride through of the symmetrical faults is presented, using passive resistive network (PRN). Moreover, in order to limit the electrical and me- chanical oscillations in the generator during unsymmetrical faults, the dual vector control (DVC) is implemented. It is found that DVC to a certain ex- tent can be used to safeguard the converter against large oscillations in rotor currents. Finally, for completeness of the thesis, a preliminary physical design of the rotating power electronic converter has been done in a finite element software called ANSYS. The thermal footprint and the cooling capability, with estimates of the heatsink and fan sizes, are presented. Besides, another variant of a rotating electronic induction machine which is based on the Lindmark concept and operating in a single-fed mode is also iv investigated. It’s steady-state model is developed and verified through exper- iments. Index Terms: Brushless doubly-fed induction generator, dual vector con- trol, dynamic model, induction machine, internal model control, Lind- mark concept, low-voltage ride-through, passive resistive network, ro- tating power electronic converter, rotating exciter, symmetrical faults, synchronous machine, thermal model, unity power factor, unsymmetri- cal faults, vector control, wind turbines. v Sammanfattning Denna avhandling handlar om modellering, analys och kontroll av en ny typ av borstlös generator för vindkraft applikation. Generatorn benämns: rotating power electronic brushless doubly-fed induction machine /generator (RPE-BDFIM/G). En stor fördel med RPE-BDFIG är att eftersläpningseffekten kan återvin- nas utan släpringar och borstar. Detta uppnås genom att införa ytterligare en maskin som kallas “exciter” tillsammans med den roterande kraftelektron- iska omvandlaren, som monterades på DFIGs axeln. Det framgår att excitern återvinner slipeffekten på mekaniskt väg, och levererar den tillbaka till nätet. Som en följd, kan släpringar och kolborstar elimineras, vilket ökar systemets robusthet och minskar underhållskostnaderna och turbinens stilleståndstid. Till att börja med utvecklats och analyseras RPE-BDFIGs dynamiska modellen. Genom den dynamiska modellen kan generatorns arbetsprincip förstås och dess funktion förklaras. Analysen har utförts vid olika hastigheter t.ex. vid ±20% av det synkrona varvtalet för generatorn. Dessutom undersöks generatorns dynamik vid yttre störningar från lastens vridmoment. Vidare härleds och analyseras maskinens stationära modell vid motordrift. Som ett nästa steg, beaktas i detalj styrningen av generatorn i det slutna systemet. Effekt och varvtalsreglering av de två maskinerna i systemet samt spänningsreglering av DC mellanled har utvecklats med principer från “in- ternal model control (IMC)”. Det framgår av resultatet att det är möjligt att upprätthålla stabiliteten i generatorn mot lastmomentstörningarna från turbinen och excitern, samtidigt som man håller en konstant DC mellan- ledsspänning på omvandlaren i rotorn. Styrningen av generatorn i det slutna systemet har också implementerats och dess regleregenskaper bekräftas genom experiment. I den tredje delen av avhandlingen, har påverkan av fel på nätet på generatorn undersökts. Generatorns drift och dess beteende under sym- metriska och osymmetriska fel studerats. Ett tillvägagångssätt presenteras för framgångsrik “ride through” genom de symmetriska felen med “passive resistive network (PRN)”. Dessutom, i syfte att begränsa de elektriska och mekaniska oscillationerna i generatorn under osymmetriska fel, har tekniken “dual vector control (DVC)” tillämpats. Man har funnit att DVC i viss ut- sträckning kan användas för att skydda omvandlaren mot de stora oscillation- erna i rotorströmmarna. Slutligen, kompletteras avhandlingen med en preliminär design av RPE i finita elementprogrammet ANSYS. Den termiska analysen och kylförmågan med uppskattningar av storlekar för kylfläns och fläkt presenterats. Dessutom, har en annan variant av den roterande elektroniska induktion- smaskinen som är baserad på Lindmarks koncept och som arbetar utan att rotorlindningen återkopplas till nätet också undersökts. En stationär modell för konceptet har utvecklats och verifierats genom experiment. Acknowledgements This project was funded by the Vindforsk Research Program who are gratefully acknowledged. First of all, I would like to thank my supervisor Professor Chandur Sadarangani for his support, encouragement, and guidance during the project. Further, I would like to express my gratitude to the steering committee members for this project; Dr. Luca Peretti, Dr. Jouko Niiranen, and Dr. Robert Chin for their valuable feedback and fruitful discussions. I want to thank Prof. Lennart Harnefors for his excellent advice on the control theory, and for continuously spending his valuable time on revising my three journal papers. I hope we can continue with the scientific work in the future. Special thanks to Prof. Hans Peter Nee for carefully reviewing this thesis. I would also like to thank Dr. Alija Cosic for his help with the equipment in the laboratory while I was working with the experimental setup. Moreover, Mats Leksell is acknowledged for solving some of the problems, which I faced during the implementation of the experimental setup. Dr. Oskar Wallmark too, is acknowl- edged for his valuable feedback on latex and on some aspects related to the control theory of the project. I would also like to thank people during my exchange visit to North Carolina State University (NCSU) Raleigh, USA. I would like to thank my supervisor there and also a co-author of my two papers, Prof. Iqbal Husain for giving me an oppor- tunity to work at FREEDM Systems Center, NCSU. Furthermore, I would like to express my gratitude to the committee at ABB corporate research, Raleigh, USA, for giving valuable feedback on my work, which I performed during my visit. For this, special thanks goes to Dr. Waqas Arshad, Dr. Ghanshyam Shrestha, and Dr. Hongrae Kim. I am grateful to all my former and current colleagues at KTH, who have been a source of help in several ways. Besides, I would like to thank Henrik Grop, Alexander Stening, Kashif Khan, Shafigh Nategh, Andreas Krings, Noman Ahmed, Yanmei Yao, Kalle Ilves, Shoaib Almas, and Lebing Jin for their company during the conferences and courses. vii viii Special thanks to E2C financial administrator Eva Petterson, system adminis- trator Peter Lönn, Jesper Freiberg, and technician Jan-Olov Brännvall (late) for assisting me with the financial, computer, and lab issues, respectively. I would like to thank Eddie for an amazing company during indoor climbing and for our excursions within Stockholm city, especially with regards to search for restaurants serving good
Load more

Recommended publications
  • Alternator Winding Temperature Rise in Generator Systems
    TM Information Sheet # 55 Alternator Winding Temperature Rise in Your Reliable Guide for Power Solutions Generator Systems 1.0 Introduction: When a wire carries electrical current, its temperature will increase due to the resistance of the wire. The factor that mostly influences/ limits the acceptable level of temperature rise is the insulation system employed in an alternator. So the hotter the wire, the shorter the life expectancy of the insulation and thus the alternator. This information sheets discusses how different applications influence temperature rise in alternator windings and classification standards are covered by the National electrical Manufacturers Association (NEMA). (Continued over) Table 1 - Maximum Temperature Rise (40°C Ambient) Continuous Temperature Rise Class A Class B Class F Class H Temp. Rise °C 60 80 105 125 Temp. Rise °F 108 144 189 225 Table 2 - Maximum Temperature Rise (40°C Ambient) Standby Temperature Rise Class A Class B Class F Class H Temp. Rise °C 85 105 130 150 Temp. Rise °F 153 189 234 270 Typical Windings Within a Generator Set’s Alternator Excitor windings Stator windings Rotor windings To fulfill our commitment to be the leading supplier and preferred service provider in the Power Generation Industry, the Clifford Power Systems, Inc. team maintains up-to-date technology and information standards on Power Industry changes, regulations and trends. As a service, our Information Sheets are circulated on a regular basis, to existing and potential Power Customers to maintain awareness of changes and
    [Show full text]
  • Power Processing, Part 1. Electric Machinery Analysis
    DOCONEIT MORE BD 179 391 SE 029 295,. a 'AUTHOR Hamilton, Howard B. :TITLE Power Processing, Part 1.Electic Machinery Analyiis. ) INSTITUTION Pittsburgh Onii., Pa. SPONS AGENCY National Science Foundation, Washingtcn, PUB DATE 70 GRANT NSF-GY-4138 NOTE 4913.; For related documents, see SE 029 296-298 n EDRS PRICE MF01/PC10 PusiPostage. DESCRIPTORS *College Science; Ciirriculum Develoiment; ElectricityrFlectrOmechanical lechnology: Electronics; *Fagineering.Education; Higher Education;,Instructional'Materials; *Science Courses; Science Curiiculum:.*Science Education; *Science Materials; SCientific Concepts ABSTRACT A This publication was developed as aportion of a two-semester sequence commeicing ateither the sixth cr'seventh term of,the undergraduate program inelectrical engineering at the University of Pittsburgh. The materials of thetwo courses, produced by a ional Science Foundation grant, are concernedwith power convrs systems comprising power electronicdevices, electrouthchanical energy converters, and associated,logic Configurations necessary to cause the system to behave in a prescribed fashion. The emphisis in this portionof the two course sequence (Part 1)is on electric machinery analysis. lechnigues app;icable'to electric machines under dynamicconditions are anallzed. This publication consists of sevenchapters which cW-al with: (1) basic principles: (2) elementary concept of torqueand geherated voltage; (3)tile generalized machine;(4i direct current (7) macrimes; (5) cross field machines;(6),synchronous machines; and polyphase
    [Show full text]
  • Low Speed Alternator Design
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by DigitalCommons@CalPoly Low Speed Alternator Design Senior Project Electrical Engineering Department California Polytechnic State University San Luis Obispo 2013 Students: Scott Merrick Yuri Carrillo Table Of Contents Section Page # Abstract................................................................................................................................i 1.0 Introduction................................................................................................................... 1 2.0 Background.................................................................................................................... 3 3.0 Requirements................................................................................................................ 6 4.0 Design and Construction................................................................................................ 8 5.0 Testing...........................................................................................................................14 6.0 Results........................................................................................................................... 20 7.0 Conclusion...................................................................................................................... 26 8.0 Bibliography...................................................................................................................28 Appendices A. Tabular Data....................................................................................................................
    [Show full text]
  • SIE Paper – V – ELECTRICAL MACHINE TECHNOLOGY Unit
    Subject Code : SIE Paper – V – ELECTRICAL MACHINE TECHNOLOGY Unit – I: DC Generators and Motors DC Generators : Types of generators – Series wound generator – Separately excited generator – Shunt wound generator – Condition for self excitation – Compound wound generator – Efficiency of DC machines. DC Motors: Back e.m.f. – Speed of a DC motor – Condition for maximum power – Armature reaction and commutation – Characteristics of D.C. motors – Motor starters – Speed control of D.C. motor. Unit – II - Transformers Transformer – Construction – Transformation ratio – Primary – No load current – Transformer on load – Effect of resistance – Equivalent circuit of static transformer – Testing of transformers – Use of transformers with measuring instruments. Unit – III: Electronic Control of AC Motors. Instability of AC motors – Variable speed induction motor drives – Torque speed characteristics of induction motors – Inverters for driving the motor – Speed control of induction motor by variable voltage - fixed frequency supply – Synchronous motor control. Unit – IV: Alternator and Amplidyne. Alternator – Construction – Operation – Frequency - Pitch factor and distribution factor – E.M.F. equation of alternator. Amplidyne – Amplification factor – Use of amplidyne in control – Amplidyne for control of voltage – Amplidyne for control of current. Unit – V: Industrial Timing Circuits. Introduction – Constituents of Industrial timing circuits – classification of timers – Thermal timers – Electro mechanical timers – Electronic timers – Classification of electronic timers – RC timing elements – Time base generators – SCR delay timer – IC electronic timer. Books for Study: 1. Industrial Electronics – G.K. Mithal – Khanna Publishers – Delhi – 15 th edition – 1992. 2. Electrical Technology – H. Cotton – CBS Publishers – Delhi. Books for References: 1. Electrical Technology – B.L. Theraja, A.K. Theraja – NIRJA construction and Development Co(p) Ltd.
    [Show full text]
  • ALTERNATORS ➣ Armature Windings ➣ Wye and Delta Connections ➣ Distribution Or Breadth Factor Or Winding Factor Or Spread Factor ➣ Equation of Induced E.M.F
    CHAPTER37 Learning Objectives ➣ Basic Principle ➣ Stationary Armature ➣ Rotor ALTERNATORS ➣ Armature Windings ➣ Wye and Delta Connections ➣ Distribution or Breadth Factor or Winding Factor or Spread Factor ➣ Equation of Induced E.M.F. ➣ Factors Affecting Alternator Size ➣ Alternator on Load ➣ Synchronous Reactance ➣ Vector Diagrams of Loaded Alternator ➣ Voltage Regulation ➣ Rothert's M.M.F. or Ampere-turn Method ➣ Zero Power Factor Method or Potier Method ➣ Operation of Salient Pole Synchronous Machine ➣ Power Developed by a Synchonous Generator ➣ Parallel Operation of Alternators ➣ Synchronizing of Alternators ➣ Alternators Connected to Infinite Bus-bars ➣ Synchronizing Torque Tsy ➣ Alternative Expression for Ç Alternator Synchronizing Power ➣ Effect of Unequal Voltages ➣ Distribution of Load ➣ Maximum Power Output ➣ Questions and Answers on Alternators 1402 Electrical Technology 37.1. Basic Principle A.C. generators or alternators (as they are DC generator usually called) operate on the same fundamental principles of electromagnetic induction as d.c. generators. They also consist of an armature winding and a magnetic field. But there is one important difference between the two. Whereas in d.c. generators, the armature rotates and the field system is stationary, the arrangement Single split ring commutator in alternators is just the reverse of it. In their case, standard construction consists of armature winding mounted on a stationary element called stator and field windings on a rotating element called rotor. The details of construction are shown in Fig. 37.1. Fig. 37.1 The stator consists of a cast-iron frame, which supports the armature core, having slots on its inner periphery for housing the armature conductors. The rotor is like a flywheel having alternate N and S poles fixed to its outer rim.
    [Show full text]
  • Doubly Fed Induction Generator with Integrated Energy Storage System for Smoothening of Output Power
    Scholars' Mine Masters Theses Student Theses and Dissertations Fall 2010 Doubly fed induction generator with integrated energy storage system for smoothening of output power Nishant Swaraj Chouhan Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Electrical and Computer Engineering Commons Department: Recommended Citation Chouhan, Nishant Swaraj, "Doubly fed induction generator with integrated energy storage system for smoothening of output power" (2010). Masters Theses. 4861. https://scholarsmine.mst.edu/masters_theses/4861 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. DOUBLY FED INDUCTION GENERATOR WITH INTEGRATED ENERGY STORAGE SYSTEM FOR SMOOTHENING OF OUTPUT POWER by NISHANT SWARAJ CHOUHAN A THESIS Presented to the Faculty of the Graduate School of the MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE IN ELECTRICAL ENGINEERING 2010 Approved by Mehdi Ferdowsi, Co-Advisor Keith Corzine, Co-Advisor Badrul H. Chowdhury Mariesa L. Crow 2010 Nishant Swaraj Chouhan All Rights Reserved iii ABSTRACT Wind energy is one of the fastest growing renewable energies in the world today. However, integration of wind power into the power system network is still confronting many challenges. One of the main challenges is the suppression of wind power fluctuations. This thesis focuses on integration of wind power with energy storage to overcome the integration challenges.
    [Show full text]
  • London Electricity Companies Had Already Supply Co
    printed LONDON AREA POWER SUPPLY A Survey of London’s Electric Lighting and Powerbe Stations By M.A.C. Horne to - not Copyright M.A.C. Horne © 2012 (V3.0) London’s Power Supplies LONDON AREA POWER SUPPLY Background to break up streets and to raise money for electric lighting schemes. Ignoring a small number of experimental schemes that did not Alternatively the Board of Trade could authorise private companies to provide supplies to which the public might subscribe, the first station implement schemes and benefit from wayleave rights. They could that made electricity publicly available was the plant at the Grosvenor either do this by means of 7-year licences, with the support of the Art Gallery in New Bond Street early in 1883. The initial plant was local authority, or by means of a provisional order which required no temporary, provided from a large wooden hut next door, though a local authority consent. In either case the local authority had the right supply was soon made available to local shopkeepers. Demand soon to purchase the company concerned after 21 years (or at 7-year precipitated the building of permanent plant that was complete by intervals thereafter) and to regulate maximum prices. There was no December 1884. The boiler house was on the south side of the power to supply beyond local authority areas or to interconnect intervening passage called Bloomfield Street and was connected with systems. It is importantprinted to note that the act did not prevent the generating plant in the Gallery’s basement by means of an creation of supply companies which could generate and distribute underground passage.
    [Show full text]
  • Compulsator Design for Electromagnetic Railgun System
    COMPULSATOR DESIGN FOR ELECTROMAGNETIC RAILGUN SYSTEM By Bryan Bennett Senior Project Electrical Engineering Department Cal Poly State University, San Luis Obispo June, 2012 ABSTRACT This project designed, fabricated, and partially tested a compensated pulsed alternator (compulsator) to power an electromagnetic rail gun (EMRG) in a multidisciplinary team. The EMRG team includes two master’s AERO students, two senior EE students, and three senior ME students. Design of the compulsator began with research through conference and research papers. This design was changed throughout the project as system analysis and component testing exposed unforeseen system limitations. While original specifications were not met, all fabricated components but one, the stator, were completed using Cal Poly’s facilities and the project’s limited available budget. Experimental verification of calculations and system modeling were not obtained because the compulsator was fully assembled at the time of this writing, but the necessary measurements and testing procedures have been outlined. i TABLE OF CONTENTS Abstract……………………………………………………………………………………………i Table of Contents…………………………………………………………………………………ii List of Figures…………………………………………………………………………………….iii List of Tables……………………………………………………………………………………..iv Acknowledgements……………………………………………………………………………….v Introduction……………………………………………………………………………………….1 Background………………………………………………………………………………………..3 Requirements……………………………………………………………………………………...6 Design……………………………………………………………………………………..………7 Total System Design……………………………………………………………...……….7
    [Show full text]
  • Excitation Systems
    Excitation Systems 10 kVA - 35 MVA alternators REGULATORS AND EXCITATION SYSTEMS ARE AT THE HEART OF INDUSTRIAL ALTERNATORS PERFORMANCE AND RELIABILITY. At Leroy-Somer, we design, test and qualify our electronic products to meet the challenges of power generation systems. Using our experience and field expertise, we provide regulation features that help protect installations from outage and failures, and our excitation systems are optimized to provide the best performance levels for any situation. EXCITATION SYSTEMS Leroy-Somer offers different excitation systems to match application requirements. An excitation system uses the alternator output to build an excitation current that is then used to power the rotating magnetic field of the rotor. This principle allows for the control of the output power. To build excitation current, a regulator needs both a supply voltage to provide power, and a measured reference voltage at output terminals to pilot the excitation. Alternator Alternator Main power outputMain power User input N Exciter output User input N Exciter U Sensing + U AVRSensing power supply + V AVR power supply AVR V AVR W W AVR outputAVR + - output + - Exciter current STATOR Exciter current STATOR Exciter Diode Exciter bridgeDiode stator bridge stator Prime Power Exciter Power systemPrime ROTOR supply system rotorExciter supply ROTOR rotor Voltage Voltage - sensing - Control sensing Comp. PID Control Exciter Comp. PID command Exciter Ref + command Main power External Ref + Main power referenceExternal reference Diagram of a complete excitation system SHUNT The SHUNT excitation system can also be completed by a booster system for larger installations to allow In SHUNT excitation systems, the AVR power supply for short circuit capability.
    [Show full text]
  • AVR Power Supplies
    Application Guidance Notes: Technical Information from Cummins Generator Technologies AGN 124 – AVR Power Supplies DESCRIPTION The simplest way to provide a power supply for an AVR is to take power directly from the stator winding’s output terminals. This system is very cost effective, offers design simplicity and so, good reliability and is the fundamental offering for small alternators in the STAMFORD range – types S0//S1, P0/P1, UC (S2/S3), S4 and HC5 (S5). Sharing the use of the alternator’s output voltage between the connected load and the AVR can be troublesome, but 70% of the world’s operating Generating Sets use this principle of operation. In Cummins Generator Technologies terminology, this type of alternator is known as Self-excited and these alternators are offered with an analogue AVR that is compatible, from the SX or AS range – SX460, AS440, AS540, AS480. The provision of a dedicated power supply to an AVR will allow the alternator’s excitation to be maintained and if required, forced, under situations where the alternator’s output connections are being subjected to gross overload or may be a short circuit fault condition within the connected electrical network. The ability to maintain and force the alternator’s excitation system to levels that will force the alternator to provide an output current of several times rated current, whilst also maintaining an output voltage as close as possible to nominal, enables the alternator to provide good response to momentary overload conditions such as motor starting and under fault conditions – current levels that should activate the affected circuits overload protection Circuit Breaker or blow a fuse – and consequently continue to supply the remaining healthy circuits and connected equipment.
    [Show full text]
  • Formulas for 3-Phase
    ____________________________________________________________ http://waterheatertimer.org/How-to-wire-3-phase-electric.html Unit 12 Three-Phase Circuits objectives A fter studying this unit, you should be able to: I Discuss the differences between three-phase and single-phase voltages. I Discuss the characteristics of delta and wye con- nections. I Compute voltage and current values for delta and wye circuits. I Connect delta and wye circuits and make mea- surements with measuring instruments. Most of the electrical power generated in the world today is three-phase. Three-phase power was first conceived by Nikola Tesla. In the early days of electric power generation, Tesla not only led the battle concerning whether the nation should be powered with low-voltage direct current or high-voltage alternating current, but he also proved that three-phase power was the most efficient way that electric- ity could be produced, transmitted, and consumed. Three-Phase Circuits There are several reasons why three-phase power is superior to single- phase power. 262 Electrical Studies for Trades 1. The horsepower rating of three-phase motors and the KVA (kilo-volt- amp) rating of three-phase transformers is about 150% greater than for single-phase motors or transformers with a similar frame size. 2. The power delivered by a single-phase system pulsates, Figure 12-1. The power falls to zero three times during each cycle. The power delivered by a three-phase circuit pulsates also, but it never falls to zero, Figure 12-2. In a three-phase system, the power delivered to Figure 12-1 Single-phase the load is the same at any instant.
    [Show full text]
  • DESIGN and DEVELOPMENT of a TWO-MEGAWATT, HIGH SPEED PERMANENT MAGNET ALTERNATOR for SHIPBOARD APPLICATION Co Huynh, Larry Hawki
    DESIGN AND DEVELOPMENT OF A TWO-MEGAWATT, HIGH SPEED PERMANENT MAGNET ALTERNATOR FOR SHIPBOARD APPLICATION Co Huynh, Larry Hawkins, Ali Farahani, and Patrick McMullen Calnetix Inc. Cerritos, CA 90703 Abstract – Conventional gas turbine generator sets consist of a high speed turbine coupled to a low speed alternator through a speed reduction gearbox. This is required to maintain the alternator output frequency at 50 Hz or 60Hz, as output frequency is directly proportional to speed. Since power is also directly proportional to speed, the conventional system is bulky and possesses a very large footprint. The advent of solid-state inverters with their unique ability to efficiently and cost effectively change the alternator output frequency has made it possible to eliminate the need to link the alternator speed to the required 50/60 Hz output frequency. This output can be produced with a high-speed alternator, eliminating the need for a gearbox and greatly reducing the size, complexity, and weight of the machine by trading speed for torque. A direct drive system in which an alternator is coupled directly to a gas turbine is much more compact and highly efficient and requires much less maintenance. In this paper we will review the design and development of a high-speed permanent magnet alternator in an advanced cycle gas turbine system for shipboard applications. In addition to the alternator’s design features, we will discuss design considerations including electromagnetic design, thermal design and structural design of high speed electrical machines, and review the alternator development including risk mitigation. INTRODUCTION The British Royal Navy has development program is to demonstrate the embarked on a development program to ACL-GTA system as a “diesel beating” evaluate advanced cycle low power gas solution, such that the ACL-GTA system turbine alternator (ACL-GTA) technology as should be able to compete in performance an alternative to the diesel generation (DG) and cost with DG systems while providing system for shipboard applications.
    [Show full text]