Product Description:

The MST251F-0040-FT-N0CN-D303 is a direct-drive torque motor produced by Bosch Rexroth Indramat within the MST Synchronous Torque Motors series. As a frameless stator and rotor assembly, it mounts directly to the driven axis and eliminates mechanical transmission, providing high continuous torque at low rotational speed for rotary tables, printing cylinders, or extruder screws in industrial automation. Because the motor couples directly to the load, it avoids the backlash and compliance that can come from belts or gear stages. Fifteen pole pairs synchronize the rotor to the stator field, which supports high torque density at modest speeds.

At rated operation, the motor turns at 400 rpm and produces 546.0 Nm of continuous torque, which corresponds to a mechanical output of 22.90 kW. To reach that operating point, the coils draw a rated phase current of 59.0 A. With a torque constant of 9.26 Nm/A, changes in current translate directly into torque at the shaft. The back EMF rises at 0.670 V/rpm, and the winding inductance is 8.9 mH, which helps smooth current ripple during regulation. Power conductors use a 16.0 mm² section, while the encoder or thermal sensor leads use 1.5 mm² conductors to support typical cable runs with low resistive loss.

Short-term overload capacity reaches 1250 Nm with a corresponding peak phase current of 177.0 A, allowing brief acceleration or shock-load events before thermal limits are reached. When the shaft is locked, the motor can hold a static load with a standstill torque of 635 Nm while drawing 66.9 A of standstill current. Copper losses depend on the phase winding resistance of 0.63 Ohm, which the drive must consider when estimating temperature rise and allowable duty cycle. These values are important in applications that require repeated indexing, rapid starts, or extended holding periods under load.