Other Motors Topics
Miniature Motors
 Figure 12 - Typical of miniature motors, this dc motor is 0.511 in. in diam and 1.24 in. long. It has an output power rating of 2.5 W at 8,000 rpm. The construction consists of Neodymium magnets, precious metal brushes, and a moving-coil rotor that uses a Rhombic-wound winding for maximum winding density. A matching 0.511-in. planetary gearhead offers five ratios from 4:1 to 1,118:1 and torque capability to 0.35 Nm continuous and 0.53 Nm intermittent.
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Filling the needs for a wider variety of power devices, new miniature motors are
announced every day. Many are less than 1/2-in. diam, even with a gearhead, Figure 12.
Typical applications include medical systems, semiconductor manufacturing, laser cutting systems,
surface-mount assembly systems, winding machines, robotic handling equipment, micrometer positioners,
motorized potentiometers, screwdrivers, scales, aircraft actuators, computer peripherals,
bar code scanners, and many others.
To maximize the power-to-weight ratio, many miniature motors are built with more costly
but higher strength magnets. Also, for reduced susceptibility to electrical noise, some are
designed with relatively low inductance.
Manufacturers often indicate motor size with a Size designation of the diameter
in 1/10s of an inch. Thus, a Size 30 motor has an outside diameter of 3 in.
For feedback, manufacturers offer a range of miniature optical and magnetic encoders,
ac and dc tachometers, and resolvers. Some companies supply line-driver encoders for
electrically noisy environments and for installations with long distances between the encoders
and the motors.
Other miniature components offered for motion systems include miniature brakes,
controls, and servo systems with appropriate software.
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