Permanent magnet field dc rotary motors have proven to be reliable drives for motion control applications where high efficiency, high starting torque, and linear speed-torque curves are desirable characteristics. A stator coil that generates magnetic flux constitutes the permanent-magnet dc servomotor; this generator is always a permanent magnet made by ferromagnetic ceramics or rare earths. An armature that includes the current carrying winding that surrounds a rotary ferromagnetic core. A commutator that provides an electric connections by means of brushes between the rotating armature winding and the external feed winding, according to a commutation logic determined by the rotor motion. It is typically a dc-to-dc converter, whereas for a brushless dc servomotor it is typically a dc-to-ac converter, whose frequency is dictated by the angular velocity of the rotor.