Integrated Motor Drives
To optimise the efficiency of electric drives it is necessary to consider the components; the power electronic converter, the electric machine and the gearbox, together. Integrated systems can be smaller and have better flexibility and thermal management. Integrated motor drives (IMDs) specifically offer advantages including lower cost of installation and higher power density. This integration concept has been adopted in various electrical machine drive systems as well as electric vehicles.
Integrated Motor Drives presents the state of research and future trends in integrated electrical motor drive technology and helps readers fill gaps in their knowledge. Chapters cover electrical machines, power converters and control techniques, adoption of wide bandgap semiconductor switching devices, thermal management, passive devices, gearboxes, research prototypes and commercial products, as well as emerging technologies and needs.
This book for electrical motor drive engineers and researchers in academia and industry, as well as advanced students and experts, is systematically written by members from leading working groups. Close collaboration between chapter authors improves cohesion and usability for advanced students.
Inspec keywords: thyristors; power electronics; elemental semiconductors; semiconductor device models; power MOSFET; power semiconductor switches; bipolar transistors; motor drives
Other keywords: motor drives; power semiconductor switches; MOSFET; thyristors; elemental semiconductors; silicon; power semiconductor devices; bipolar transistors; power electronics
Subjects: General electrical engineering topics; Thyristors and silicon controlled rectifiers; Power convertors and power supplies to apparatus; Insulated gate field effect transistors; Drives; Power semiconductor devices; Semiconductor device modelling, equivalent circuits, design and testing; Elemental semiconductors; Bipolar transistors; Relays and switches
- Book DOI: 10.1049/PBPO178E
- Chapter DOI: 10.1049/PBPO178E
- ISBN: 9781839531866
- e-ISBN: 9781839531873
- Page count: 374
- Format: PDF
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Front Matter
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1 Introduction
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The integration of electrical components is receiving increased attention in the field of power electronics and electrical drives research. The integrated motor drive (IMD) emerged as a structural integration of an electric motor with a motor drive as a single unit, with at least 20% less volume and 30-40% lower overall system costs of installation and manufacturing. The elimination of expensive components such as shielded connection cables, a separate housing for the power converters, a centralised controller cabinet, and high-voltage and current bus bars is the primary driving force in increasing the power density and lowering the cost. It also leads to an improved electromagnetic interference (EMI) behaviour due to the direct connection of the motor to the drive without additional cables.
Depending on the innovative integration concepts, integrated systems are commonly smaller, have greater structural flexibility and enhanced thermal management, while ensuring that system integration and modularity are not mutually exclusive. When IMDs are employed as a direct replacement of less efficient, fixed speed, direct on-line motors, they offer significant advantages, including lower cost of installation and enhanced system efficiency when compared to discrete motor drive systems.
There are varying degrees of integration found under the overall field of integrated machines, beginning with very mild integration - whereby the IMD is essentially two identifiably separate entities (i.e., the motor and the adjustable speed drive) with minimal integration beyond mechanical fixing - through to IMDs with very intricate integrations whereby the multi-physics interactions are deeply interlinked and highly complex. The philosophies and impacts of various degrees of integration are ongoing debates in the field.
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2 Electrical machines for an integrated drive
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The electrical machine typically comprises the largest and heaviest component of an integrated drive and hence deserves to have a chapter devoted to it. This chapter will not attempt to give a comprehensive review of all electrical machines - a topic which could occupy several books in its own right. Instead, it will focus on aspects of electrical machines which are particularly relevant to integrated drives.
The chapter covers two main topics. It first deals with construction methods and modularity. With close integration, it is possible to split the system into different modules and the case to stay with three phases becomes weaker. This creates a large range of options and topologies, as discussed in Section 2.2. The second topic concerns materials: advances in materials have had a major impact, particularly with regard to insulation systems, winding technology and magnetic materials. Sections have hence been dedicated to each of these in turn.
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3 Power converter and control techniques
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In Chapter 2, the authors have discussed the fundamentals of electrical machines and their application in integrated motor drives (IMDs). In order to serve electrical machines and help them achieve their designed performance, associated power electronics, sensors, controllers, and the advanced control techniques will be introduced in this chapter.
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4 Wide bandgap semiconductor switching devices in integrated motor drives
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Since the introduction of silicon-based thyristors in 1957, researchers in the field of power semiconductor devices have achieved remarkable progress. In the late 1960s, the gate turn-off thyristor (GTO) made it possible to turn off the latching thyristor devices using their gate terminals, enabling switching frequencies exceeding 1 kHz. In the mid-1970s, new silicon bipolar junction transistors and metal-oxide-semiconductor field-effect transistors (MOSFET) were introduced, pushing switching frequencies upward above 10 kHz. The insulated-gate bipolar transistor (IGBT) was developed in the 1980s with combined features of the MOSFET and bipolar transistor that made it an appealing choice for many power electronics applications, including motor drives. Today, IGBTs are the dominant power switching devices for power electronic converters operating at voltages greater than 600 Vdc.
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5 Thermal management of integrated motor drives
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When reviewing technology related with integrated motor drives (IMDs), it is natural to look first at the most recent developments in high-specific-output and high efficiency electrified propulsion, on-board power generation and actuation. All of these have been recently receiving increased attention in the context of global efforts towards the net-zero emission and more sustainable society. Particularly, transportation (future mobility) has been undergoing dynamic transformative changes, with numerous technological challenges to be addressed [1,2]. Here, both system integration and thermal management have been identified as essential to development of the next-generation IMDs. Interestingly, when exploring the motor drive technology, it is evident that the concept of IMDs is not new. IMDs have been with us for much longer than one might think. The early examples of integrating electronics with electrical machines include both automotive and aerospace applications introduced in the 1960s [3,4]. Here, car alternators and aircraft generators were the first to combine both electrical machine and power electronics (three-phase full-wave discrete diode rectifiers) in a single package to provide a specific application driven, technologically competitive products. Figure 5.1 presents the early design solutions including the rotating rectifier assembly of an actively air-cooled brushless AC generator [3] and alternator assembly [5] for aerospace and automotive applications, respectively.
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6 Passive devices
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The use of passive devices within an integrated drive has been discussed in this chapter. The largest components used are for energy storage are largely determined by the supply from which the motor is fed and are used to provide a stable DC link voltage required for motor control. The materials used in these components become more expensive and can be difficult to achieve robust operation and long lifetime operation due to the high temperatures experienced within the integrated drive.
While the drive and motor are integrated, careful power system design can improve the size, weight, and cost of the integrated machine. Special attention is required to minimize the parasitic capacitances and loop inductances within the fast switching nodes in the circuit. This will reduce the number and size of additional filter components which must be used to ensure reliable operation and to prevent interference with other equipment. The use of WBG semiconductor devices enables the efficient and compact motor drive, but the higher frequencies involved place additional importance on designing for EMC and testing to confirm compliance. More integrated filter configuration for motor drive application should be considered. Further material research is required to continue to push the limits of the passive devices and develop components which can operate at higher temperatures with ever more compact size.
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7 Gearboxes
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Gears and gearboxes are used to convert torque and speed to optimize the overall performance of a transmission system. A gearbox reduces the cost of manufacture and optimizes the operating efficiency by matching the performance characteristics of the prime mover, such as a combustion engine or electric motor, with the vehicle torque and speed requirements.
Modern automotive transmissions require high power density, low weight, high efficiency, low noise, and reduced manufacturing costs. This can only be achieved with the application of precise and effective gearbox design, manufacture, high quality material and heat treatment and effective quality control.
Gear technology is challenging and often poorly understood, and the objective of this chapter is to direct engineers to appropriate gear related resources and to improve their understanding in general. Throughout this chapter, we will use International Standards Organization (ISO) terms and symbols which are in effect the international language of gears. ISO standards and their supporting Technical Reports provide a useful source of reference material for those involved with gears and gearboxes and will be referenced throughout.
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8 Research prototypes and commercial products
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In this chapter, we will review several of cutting-edge integrated motor drive (IMD) research prototypes and a commercial product.
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9 Emerging technologies and needs
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Literature and advanced industry applications are the main source of information when it comes to spot emerging technologies and new trends. This is valid in every research field, and integrated motor drives make no exception.
However, there are two main risks in producing a list of the most novel technologies currently published, or available on the market. First, this list would be an instantaneous frame destined to become outdated. Second, being a selection from a very broad range of examples, it is likely to be incomplete. An outdated and incomplete list of manufacturing processes would not make a great service to the reader and the community. A method, on the other hand, that can be used to understand weather a certain new concept can be beneficial for IMDs development, can be a pragmatic and profitable aim for this chapter.
To this end, the main challenges in the design, manufacturing, and operation of IMD are here recalled and discussed. Some of these challenges pose limitations in the application of IMD to higher power level or to production process scalability. A representative selection of emerging concepts is then considered, maintaining the focus on the challenge that they address. In this way, it is possible to include in the selection, concepts that still have not been applied to the IMD world but are eligible as technology enabler. These emerging concepts are presented following a sensible classification: design concepts and assembly technologies.
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Back Matter
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