Electric traction – Motive power and energie supply

Abstract

This book has evolved from the lecture series “Elektrische Bahnen” (“Electric railways”) which has been held at Ruhr-Universität Bochum since 1996. Its primary audience are students of electrical energy technologies, control engineering and mechanical engineering as well as young engineers of electrical engineering, especially in the fields of power electronics, in railway industry and in railway-operating companies. The book intends to convey mechanical fundamentals of electric railway propulsion, which includes rail-bound guidance, transmission of traction effort from wheel to rail under the influence of non-constant levels of adhesion and the transmission of motor torque to a spring-mounted and thus sliding drive set. The focal point of the book will be the disposition of electric traction units powered by threephase induction motors. We shall discuss the stationary and dynamical behaviour of the squirrel-cage induction motor and the principle and construction features of pulse-controlled inverters, as well as scalar and field-oriented control systems and four-quadrant power converters, feeding the DC link of the inverters. As is appropriate to the lesser importance these drive systems have nowadays, we will consider DC and AC commutator motors only in a cursory fashion, as well as their voltage control. By example, we will take a look at high-performance locomotives, high-speed trains, diesel-electrically powered locomotives and commuter passenger systems. Since the specific railway energy supply network being separate from the national power utility is a key factor in operating electrical railway systems, chapter 13 will offer a detailed look at the various systems of railway power supply, under special consideration of converter technology in this field as, for example, the line interference of inverter-fed traction units (see chapter 14). Chapter 15 features an abridged overview on the most important systems of field-oriented control of induction motors and about an innovative speed-sensorless control approach for induction motor drives, coming now into the commercial phase. Chapter 16 suggests further reading, while chapter 17 will provide lecture-oriented exercise (including sample solutions). The Anglo-american reader may notice that the lion´s share of examples has been derived from central European (German, Swiss, Austrian) samples of Electric Traction. This is mainly due to the author´s personal experience as well as the fact that most fundamental research, design and construction of locomotives utilizing power electronics took place in these countries, notably with BBC and Siemens. We wish to apologize that British and American locomotives only feature rarely; however, an approach based on personal experience appeared to be the most sensible way to tackle the subject. The translation follows the International Electrotechnical vocabulary (IEV, [31]) of IEC and the UIC Railway Dictionary [32]. Corresponding to the dominant use in international technical and scientific literature, the British English term ‘bogie’ will be used for the German word ‘Drehgestell’ and not the term ‘truck’, usual in American English. Finally, please excuse the use of German symbol standards in formulae and diagrams, since the vast number of variables involved would make a complete exchange a daunting task.