Limited Angle Torquers (LATs)

Limited Angle Torquers (LATs)

The Limited Angle Torquer (LAT) is a DC brushless motor with a permanent field assembly (rotor) and a wound armature assembly (stator).  LATs produce torque within a limited range of motion without commutation.  When a fixed is applied, the motor will develop maximum torque at its peak torque position.  Torque usually decreases as the rotor moves away from the maximum torque position.  Unless the current polarity is reversed torque decreases until the LAT's angular limits are reached.

There are two types of LAT designs; slotted and toroidal.  The slotted design has winding slots in the laminated core.  The toroidal design has a solid or laminated core without sots, and wire turns are wrapped around the core.  Usually the toroidal core is molded to protect the winding.

Slot wound LATs, due to slot teeth and a smaller air gap, have more cogging and friction than a toroidally wound LAT.  Torque is generally sinusoidal with respect to rotor position.  Slot wound LATs can have a much higher motor constant than the same size toroidal design.