Product Description:

The U12M4LR is a disc-armature DC servo motor produced by Kollmorgen within the ServoDisc Pancake DC Motors series. Its flat rotor geometry shortens the axial length, providing a compact actuator for precision position or velocity loops in semiconductor handlers, indexing tables, and other automated axes. The permanent-magnet field and brush commutation provide bidirectional torque through simple drive electronics, making the unit suitable for applications that require high torque density in a shallow package.

At a terminal voltage of 22 V, the motor reaches a rated speed of 3000 rpm while delivering 79 N-cm of torque and 249 W of mechanical output. The required continuous armature current is 15.8 A, and the winding resistance is 0.305 Ω. These electrical values allow the resulting copper loss to be considered during thermal analysis. A torque constant of 5.52 N-cm/A links controller current commands to shaft torque, while the back-EMF constant of 5.77 V/krpm indicates the voltage generated during regeneration. Heat moves from the winding to the ambient environment through a 1.27 °C/W thermal path at rated speed. Dynamic friction is approximated by a viscous damping factor of 1.2 N-cm/krpm. The housing measures 139.7 mm in diameter and 53.3 mm in length, while the complete assembly weighs 3.6 kg, allowing direct installation on compact stages.

During sudden changes in load, the armature can accept 160 A for short intervals and produce up to 864 N-cm of torque before saturation. This overload capacity allows axes to accelerate heavy loads quickly, provided the motor remains below its maximum speed of 6000 rpm. Rapid start-and-stop movements can be performed without gearing by using the high peak-to-continuous torque ratio, but the drive controls must limit the duty cycle to keep the average temperature within the permitted range. The thin profile positions the magnets close to the load flange, reducing reflected inertia and improving servo response in pick-and-place or test-handling equipment.