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5
Brushed direct-current motors
Chapter outline
5.1 Review of motor theory ............................................................................................................ 136
5.2 Direct-current motors ................................................................................................................. 137
5.2.1 Ironless-rotor motors ........................................................................................................ 137
5.2.2 Iron-rotor motors .............................................................................................................. 139
5.2.3 Torque motors................................................................................................................... 139
5.2.4 Printed-circuit motors ....................................................................................................... 140
5.3 Drives for d.c. brushed motors.................................................................................................. 143
5.3.1 Linear amplifiers................................................................................................................ 143
5.3.2 Pulse width modulated servo drives ............................................................................... 145
5.3.3 Analysis of the bipolar PWM amplifier .......................................................................... 147
5.3.4 PWM amplifiers................................................................................................................. 151
5.4 Regeneration ............................................................................................................................... 157
5.5 Summary...................................................................................................................................... 163
Reference ............................................................................................................................................ 163
Direct-current (d.c.) brushed motors, either with a separately excited field or with a
permanent-magnet rotor, have been used within variable speed drives for a considerable
period of time. This class of motors has inherently straightforward operating charac-
teristics, flexible performance, and high efficiency; these factors together with the long
development history have resulted in brushed d.c. motors being used as a standard
within many industrial applications. With recent developments in magnetic technology
and manufacturing techniques, a wide range of d.c. brushed motors are available for use
by servo system designers. Even with the latest developments in brushless d.c. and vector
controlled a.c. motors, brushed d.c. motors have a number of advantages that will ensure
their use by system designers for a considerable time to come.
This chapter reviews both the types of motors which are presently available and the
options for their control. Brushed d.c. permanent-magnet motors can be obtained
commercially in the following forms:
Ironless-rotor motors.
Iron-rotor motors.
Torque motors.
Electric Drives and Electromechanical Systems. https://doi.org/10.1016/B978-0-08-102884-1.00005-4 135
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