Modeling and Control of DC Machines
The brushed DC machine, which derives its excitation flux from a field winding or permanent magnets, remains commercially relevant in the field of drives. This despite the influx of brushless drive technologies which offer a maintenance-less alternative t
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Modeling and Control of DC Machines
The brushed DC machine, which derives its excitation flux from a field winding or permanent magnets, remains commercially relevant in the field of drives. This despite the influx of brushless drive technologies which offer a maintenance-less alternative to the commutator/brush assembly, which is an inevitable component of the brushed DC machine. Well-established motor manufacturing techniques, together with low-complexity power electronic converters, have been instrumental in retaining its popularity in a diverse range of applications. For household goods and automotive products, the use of low cost, brushed permanent magnet motors remains virtually unchallenged. In particular, the brushed DC series machine known as the universal machine is widely deployed in domestic appliances and starter motors. In the field of manufacturing automation, small high-dynamic brushed servo drives continue to play an essential role. Furthermore, due to the apparent simplicity, the brushed DC machine can still be found in some medium-power applications where dynamic performance is considered not to be a key issue. Given these considerations, it is prudent to consider the modeling and control of these machines in some detail. From a didactic perspective, there is decided merit in examining the brushed drive concept first. This approach provides the opportunity to introduce and demonstrate some basic modeling and model based control aspects, which are highly relevant for AC drives that utilize rotating field machines. The inversion of the current source model, an approach which is one of the cornerstones of this book, is initially demonstrated for a brushed DC drive. In addition, attention will be given to the development of control strategies which ensure that drive operation is kept within the drive envelope dictated by voltage or current constraints. In this context, field weakening strategies for separately excited machines are introduced, together with a set of PLECS based tutorials.
© 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_5
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5 Modeling and Control of DC Machines
5.1 Modeling of Brushed DC Machines To give a brief review of DC machine concepts, the cross-sectional views as well as the symbolic and generic models are presented together with the relevant equations. A more extensive examination can be found in [3]. A comprehensive treatment of basic machine concepts for the uninitiated reader is given, for example, in [1] and [2]. Cross-sectional views of two typical one pole pair brushed DC machine examples, namely the separately excited DC machine and the permanent magnet DC machine, are given in Fig. 5.1. Common to both machines is the armature, which is the rotational component of the motor that is linked to the brush/commutator assembly which ensures that the current distribution in said armature is stationary with respect to the αβ coordinate system that in turn is tied to
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