Siemens 1FK7084-2AC71-1QB0 SIMOTICS S 1FK7-CT 3.1 kW 20 Nm 2000 rpm Holding Brake Servo Motor

The Siemens 1FK7084-2AC71-1QB0 is a SIMOTICS S 1FK7-CT synchronous servo motor rated 3.1 kW, delivering 20 Nm standstill torque (M0, 100K duty) at a 2000 rpm rated speed with an 8-pole, 6.7 A design. It is naturally cooled, IMB 5 flange-mounted, and fitted with an absolute single-turn 20-bit encoder on a DRIVE-CLiQ interface plus an integrated holding brake, for IP64-rated position retention on vertical axes.

Selection Notes

The -2AC71 code sets this motor to a 2000 rpm rated speed within the 1FK7-CT frame, versus the higher-speed -2AF71 winding rated to 3000 rpm at the same 20 Nm standstill torque; the 2000 rpm winding trades top speed for a higher 2.36 Nm/A torque constant, useful where current headroom on the drive is limited. The -1QB0 suffix adds the integrated holding brake, which raises moment of inertia to 35.5 kgcm2 and motor weight to 21.3 kg compared with the non-brake configuration in this frame, so this figure needs to go into the drive's inertia-matching calculation. Pick this brake configuration for vertical or gravity-loaded axes that must hold position when the servo drive de-energizes; on a horizontal axis without a fail-safe holding requirement, the non-brake version in the same frame carries less inertia. The 68,000 Nm/rad torsional stiffness and 1.02 ms mechanical time constant still support fast point-to-point moves once the brake's added inertia is accounted for in the position loop tuning.