f* 3 ATkLL- -- A 31 LAPPEENRANNAN TEKNILLINEN KORKEAKOULU Energiatekniikan osasto LAPPEENRANTA UNIVERSITY OF TECHNOLOGY Department of Energy Technology LTKK RESEARCH REPORT EN A-33 DESIGN OF A SWITCHED RELUCTANCE GENERATOR Thomas Heese Juha Pyrhonen % FOREIGN SALES PROHIBITED 1996 ISBN 951-764-077-3 H ISSN 0785-823X DISTRIBUTION RESTRICTED TO U S. ONLY '» DISCLAIMER Portions of this document may be illegible electronic image products. Images are produced from the best available original document. ABSTRACT LAPPEENRANTA UNIVERSITY OF TECHNOLOGY Department of Energy Technology Section of Electric Power Engineering Thomas Heese, researcher Juha Pyrhonen, associate professor, doctor of technology DESIGN OF A SWITCHED RELUCTANCE GENERATOR LUT, Department of Energy Technology, September 1996, 105 pages, 61 pictures, 10 tables, 1 appendix Research Report EN A-33 ISBN 951-764-077-3 ISSN 0785-823X UDK: 621.313 Key Words: Electrical Machines, Switched Reluctance Machines, Generators This paper presents the design of a low voltage switched reluctance generator for variable speed applications showing the design of its construction and commutation unit. For the realisation of the control system the control strategy is presented. The principle and the theory of switched reluctance generators are described in this context. Also an overview of existing generator technology for these applications is given. The results gained suggest that switched reluctance machines can also advantageously be used as generators if the generating operation is considered within the design process. Compared with the existing technology a higher output power and efficiency is reached over the whole speed range. Lappeenranta, September 1996 Thomas Heese, Juha Pyrhonen J 2 Contents Preface .............................................................................................................................................1 Contents ..........................................................................................................................................2 List of Symbols .............................................................................................................................4 Tiivistelma ...................................................................................................................................... 9 1 Introduction ...........................................................................................................................10 2 Generators for Variable Speed Applications ..................................................................12 2.1 DC Generator ............................................................................................................... 13 2.2 Alternator ....................................................................................................................... 15 2.3 Weak Spots of Existing Technology ........................................................................18 2.4 Supposed Improvements and Advantages of Switched Reluctance Technology21 3 Principle and Theory of Switched Reluctance Generators ......................................... 24 3.1 Construction ................................................................................................................. 24 3.1.1 Basic Characteristics ........................................................................................... 25 3.1.2 Envelope and Internal Dimensions .................................................................. 27 3.1.3 Pole Geometry .....................................................................................................30 3.1.4 Windings ............................................................................................................... 32 3.2 Working Principle........................................................................................................32 3.2.1 Rotor Position Dependency............................................................................... 33 3.2.2 Torque and Currents.......................................................................................... 37 3.2.3 Mathematical Description .................................... 39 3.2.4 Energy Conversion ............................................................................................. 41 3.3 Commutation Unit.....................................!................................................................ 46 3.3.1 Classic Converter ................................................................................................47 3.3.2 (»+l)-switch converter ..................................................... :...............................48 3.3.3 Boost and Buck Converter ............................................................................... 49 3.3.4 Bifilar Winding Converter ..................................................................................51 3.3.5 Other Converter Topologies .............................................................................52 3.4 Dynamic Operation ......................................................................................................52 3.4.1 Single-Pulse Operation ....................................................................................... 53 3.4.2 Chopping .............................................................................................................. 55 3.5 Control System.............................................................................................................55 3.5.1 Structure............................................................................................................... 56 3.5.2 Control Modes and Strategy .............................................................................56 3.5.3 Sensorless Control ...............................................................................................58 Contents 3 4 Generator Design ................................................................................................................ 59 4.1 Construction ................................................................................................................. 60 4.1.1 Basic Characteristics ............................................................................................62 4.1.2 Envelope and Internal Dimensions ................................................................... 63 4.1.3 Pole Size and Geometry ......................................................................................66 4.1.4 Winding ................................................................................................................. 68 4.1.5 Further Estimations ............................................................................................ 72 4.2 Commutation Unit................................................................................................. 73 4.2.1 Topology ................................................................................................................75 4.2.2 Transistors ............................................................................................................ 76 4.2.3 Diodes .................................................................................................................... 78 4.2.4 Zener Diode ................................................................... 79 4.3 Control System....................................................................................................... 80 4.3.1 Control Strategy ................................................................................................... 80 4.3.2 Sensing .................................................................................................................. 82 5 Simulation Results...............................................................................................................84 5.1 Input...............................................................................................................................85 5.2 Output..............................................................................................................................90 5.3 Phase Current................................................................................................................93 5.4 Efficiency.......................................................................................................................95 5.5 Losses ..............................................................................................................................97 6 Conclusion and Prospects ...................................................................... 101 7 References............................................................................................................................102 Appendix A: Measuring Results of an Alternator .........................................................106 Appendix B: True Scale Figures of the Generator ....................................................... 118 Appendix C: Conclusion of Characteristic and Dimension Values ..........................120 Appendix D: Tables of the Simulation Results..........................................................121 List of Symbols •'i comer comer area Acu winding copper area Acu+insul cross sectional winding area with insulation Acu wire nominal cross sectional copper area Ainsul insulation area Ar area of rotor cross section Aglotr rotor slot area AglotS stator slot area Aslotsnet net stator slot area A wire cross sectional wire