Microstep motors

  Microstep motors are usually hybrid motors. The rotor consists of an arbor, bearings, and one, two, or three sets, or stacks, of toothed cylindrical magnets. The toothed stator is wound so that alternate poles are driven by two separate phase currents. This results in a 200 step per rev motor that, when the two windings are energized proportionately, enable the motor to make 125 intermediate steps between each full step. Thus, using digital logic control and bipolar pulse width modulation, the motor makes 25,000 microsteps per rev.

VR step motors
  The variable reluctance (also termed “switched reluctance”) step motor is also constructed with a toothed rotor
and stator. There are not, however, any magnets in the rotor. Depending on the stator design, two, three, or four phase
windings may be used.

MINIATURE MOTORS
  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-toweight 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 mag-
netic 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.