A special type of brushless motor is called a limited-angle torquer (LAT). LATs are constrained to produce torque through a rotation angle of less than 180 degree, But they are widely used to operate servovalves, direct laser mirrors, position missile-guidance radar antennas, open shutters for heat-seeking sensors, and power other systems that rotate through small angles.
The rotor in a limited-angle torquer carries field magnets, and the stator supports armature windings (similar to the construction of conventional brushless motors). LATs, however, are wound single phase, unlike conventional brushless types, which are typically wound for two or three-phase operation. Single-phase construction eliminates the need for commutation circuitry.
Conventional brushless motors can also be used for limited-angle service. But when conventional three-phase brushless motors are used as LATs, only two of the three leads are used.
Armature windings in some limited-angle torquers are embedded in slots around the inside periphery of a laminated stator, a construction similar to that used with conventional brushless motors. In another design, the armature is toroidally wound on a slotless stator. Here, some stators are laminated and others are solid