Brushless dc (BLDC) motors are used in countless applications.
Many engineers today are looking to improve the performance of
their BLDC-powered systems, and a new trend is emerging: An
increasing number of BLDC motors are being built with more rotor
pole pairs and stator phases. Motors with this construction
offer high torque and stability. However, as we'll explore,
getting the most from these new motors requires that they be
used with optical encoders.  BLDC motor basics  Brushless dc
motors consist of two major components — the rotor and stator.
The rotor is covered with permanent-field magnets, while the
stator consists of an armature winding on the soft metal,
separated by 120 electrical degrees (°e). The system's drive
provides phase-to-phase current flow through the stator winding,
in turn generating a magnetic field to propel the rotor as
magnetic fields of different phases are created. These phases
are identified as U, V, and W.  For motors that directly drive
loads, the torque/speed ratio must be f