Switched Reluctance Drive Systems
The term switched reluctance (SR) may to the uninitiated reader convey the notion that the reluctance of the machine is switched. In reality the magnetic reluctance of the machine is rotor angle dependent and the term switched refers to the electronic com
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Switched Reluctance Drive Systems
The term switched reluctance (SR) may to the uninitiated reader convey the notion that the reluctance of the machine is switched. In reality the magnetic reluctance of the machine is rotor angle dependent and the term switched refers to the electronic commutation of the electrical phases by means of a power electronic converter. Torque production based purely on variation of the magnetic reluctance is well established and the first patent based on this approach stems from 1839 [24]. Despite being one of the oldest known machine concepts, it has not been able to maintain its hierarchical position in comparison to machines which utilize the Lorentz force as a basis for torque production. Since the development of power electronics, there is no readily identifiable single reason for this sequence of events, but it is perhaps useful to consider some of the factors which may well have facilitated this state of affairs. From a learning perspective, the process of familiarization of, for example, a vector controlled induction machine drive concept starts from basic modeling principles, leading to a model based control concept. This model based approach to develop torque controllers (field-oriented control) may in turn be followed by a familiarization process that encompasses some form of simulation and practical application. To facilitate this learning process, the reader may acquire an “off-theshelf” drive concept, with a machine which is well defined in terms of its model and parameters. If we attempt to emulate this learning process for a switched reluctance drive, the process is less well defined simply because this type machine is more difficult to model. Furthermore, the torque production concept of the switched reluctance machine (SRM) is considerably different to the Lorentz force based machine. The latter may for many readers have a degree of familiarity given the fact that the basic principles are often taught at an early stage of education. The learning curve to mastering SR technology is steep and comparatively unfamiliar given the need to understand a machine concept in which non-linear effects, i.e., magnetic saturation, play a key role. The inevitable non-linear modeling techniques required to handle saturation are not standard and machine characteristics are not © Springer Nature Switzerland AG 2020 R. W. De Doncker et al., Advanced Electrical Drives, Power Systems, https://doi.org/10.1007/978-3-030-48977-9_10
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10 Switched Reluctance Drive Systems
readily quantified by few parameters. Today, there are commercial tools available for modeling and designing switched reluctance machines, given the need to optimize the drive with respect to the application. Notwithstanding the above, SR drive technology is increasingly seen as a cost saving alternative to conventional Lorentz force based machines. One of the key reasons for this is the simple doubly salient machine concept, devoid of permanent magnets, or any form of winding or squirrel cage on the rotor. Consequent
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