Miller, T.J.E. - SPEED's Electric Motors

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SPEED's Electric Motors An outline of some of the theory in the SPEED software for electric machine design with problems and solutions © TJE Miller, University of Glasgow, 2002 SPEED's Electric Motors Contents Chapter 1 Sizing, gearing, cooling, materials and design Chapter 2 Brushless permanent-magnet machines Chapter 3 Induction machines Chapter 4 Switched reluctance machines Chapter 5 Commutator machines SPEED's Electromagnetic Primer Problems and solutions 1. Sizing, gearing, cooling,
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  SPEED 's Electric Motors An outline of some of the theoryin the SPEED  software for electric machine design with problems and solutions © TJE Miller, University of Glasgow, 2002  SPEED's Electric Motors ContentsChapter 1 Sizing, gearing, cooling, materials and designChapter 2 Brushless permanent-magnet machinesChapter 3 Induction machinesChapter 4 Switched reluctance machinesChapter 5 Commutator machines SPEED  's Electromagnetic PrimerProblems and solutions  1. Sizing, gearing, cooling, materials and design 1.1 Motion control systems....................................................1.21.2Why adjustable speed?....................................................1.21.3 Large versus small drives.................................................1.41.4 Structure of drive systems.................................................1.41.5 Drive system requirements................................................1.51.6 New technology..........................................................1.51.7 Which Motor ?...........................................................1.81.8 Sizing..................................................................1.141.9 Gearing................................................................1.181.10 Cooling.................................................................1.201.11Intermittent operation...................................................1.271.12Permanent magnet materials and circuits..................................1.301.13 Properties of electrical steels..............................................1.391.14 Machine and drive design................................................1.421.15 Computer-aided design...................................................1.43  Fig. 1.1Flow process controlled by recirculation can produce energy losses in the flow control valve. 1. SIZING, GEARING, COOLING, MATERIALS and DESIGN 1.1   M OTION CONTROL SYSTEMS Technology is so saturated with developments in microelectronics that it is easy to forget the vitalinterface between electrical and mechanical engineering. This interface is found wherever mechanicalmotion is controlled by electronics, and pervades a vast range of products. A little considerationreveals a large and important area of technology, in which motor drives are fundamental. In Japan theterm 'mechatronics' is applied to this technology, usually with the connotation of small drives. In thewest the term 'motion control system' is often used for small controlled drives such as position orvelocity servos. In the larger industrial range the term 'drive' usually suffices.Many engineers have the impression that the technology of motors and drives is mature, even static.But there is more development activity in drives today than at any time in the past, and it is notconfined to the control electronics. Two important reasons for the development activity and theincreasing technical variety are:(1)Increasing use of computers and electronics for motion control. Automation demands driveswith a wide variety of physical and control characteristics.(2)New technology in power semiconductors, sensors, integrated circuits, and microcontrollers,facilitating the development of nonclassical motors such as brushless DC motors, steppers andswitched reluctance motors in a wide variety of designs. 1.2W HY ADJUSTABLE SPEED ? Three common reasons for preferring an adjustable-speed drive over a fixed-speed motor are :(a)energy saving;(b)velocity or position control; and(c)amelioration of transients.(a) Energy saving . In developed economies about one-third of all primary energy is converted intoelectricity, and about two-thirds of that is re-converted in electric motors and drives, mostlyintegral-kW induction motors running essentially at fixed speed. If a constant-speed motor is used todrive a flow process (such as a fan or pump), the only ways to control the flow rate are by throttling orby recirculation, Fig. 1. Since the motor runs at full speed regardless of the flow requirement, therecan be excessive energy losses in the recirculation valve. Similar considerations apply to the controlof airflow by adjustable baffles in air-moving plant.
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