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Elsevier Inc.
DOI: 10.1016/b978-075067723-3/50008-8
  • Design


Publisher Summary This chapter focuses on basic types of motors and their applications in embedded systems. The variable-reluctance (VR) stepper has a soft iron rotor with teeth and a wound stator. The hybrid stepper essentially adds teeth to a permanent magnet motor, resulting in better coupling of the magnetic field into the rotor and more precise movement. All steppers work by creating a rotating magnetic field in the stator, to which the rotor aligns itself. There are two types of stator winding methods for stepper motors: bipolar and unipolar. Many stepper motors exhibit a sudden loss of torque when operating at certain step rates. This occurs when the step rate coincides with the oscillation frequency of the rotor. Many designs need to sense the current through the stepper motor coils. The usual method for doing this is to place a small-value precision resistor in series with the ground lead of the driver circuit. Stepper motors driven with constant current drive are more likely to have resonance problems at low step rates.

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