Page 80 - Electric Drives and Electromechanical Systems

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Power transmission and sizing

Chapter outline
3.1 Gearboxes...................................................................................................................................... 74
3.1.1 Conventional gears ............................................................................................................. 74
3.1.2 Planetary gearbox............................................................................................................... 78
3.1.3 Harmonic gearbox............................................................................................................... 80
3.1.4 Cycloid gearbox................................................................................................................... 81
3.2 Lead and ball screws .................................................................................................................... 82
3.3 Belt drives ...................................................................................................................................... 85
3.4 Bearings.......................................................................................................................................... 88
3.4.1 Conventional bearings........................................................................................................ 88
3.4.2 Conventional linear bearings............................................................................................. 90
3.4.3 Friction in conventional bearings...................................................................................... 91
3.4.4 Air bearings ......................................................................................................................... 91
3.4.5 Magnetic bearings .............................................................................................................. 92
3.5 Couplings ....................................................................................................................................... 93
3.6 Shafts.............................................................................................................................................. 95
3.7 Linear drive considerations.......................................................................................................... 97
3.8 Review of motor-drive sizing...................................................................................................... 98
3.8.1 Continuous duty................................................................................................................ 100
3.8.2 Intermittent duty .............................................................................................................. 101
3.8.3 Inability to meet both the speed and the torque requirements................................. 104
3.8.4 Linear motor sizing........................................................................................................... 104
3.9 Summary...................................................................................................................................... 106
Reference ............................................................................................................................................ 106

While the previous chapters have considered the analysis of a proposed motor-drive
system and obtaining the application requirements, it must be recognised that the
system comprises a large number of mechanical components. Each of these compo-
nents, including couplings, gearboxes and lead screws, will have their own inertias and
frictional forces, which all need to be considered as part of the sizing process. This
chapter considers power transmission components found in typical applications, and

Electric Drives and Electromechanical Systems. https://doi.org/10.1016/B978-0-08-102884-1.00003-0 73
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