Drive selection memo — the 18.5 kW G120C with STO
The Siemens 6SL3210-1KE23-8UB0 is a SINAMICS G120C compact drive rated for 18.5 kW output with a 150% overload capability for 3 seconds, sized for a standard 4-pole induction motor on a 380-480 V 3-phase supply. The unfiltered input stage accepts 380-480 V 3AC +10/-20% at 47-63 Hz, so it suits European and North American line voltages without a step-down transformer. Integrated Safe Torque-Off (STO) is built in — no separate safety module required for the stop function, which simplifies the safety circuit and reduces panel wiring. The onboard I/O gives 6 digital inputs, 2 digital outputs, 1 analog input, and 1 analog output, enough for basic speed/start-stop control without an expansion card. Fieldbus is USS/MODBUS RTU over the integrated RS-485 port; for PROFINET or EtherNet/IP you would add a communication board.
Safety integration — STO without a separate card
Safe Torque-Off is integrated on the power stage, not as an option slot. That means the drive itself provides the SIL 3 / PL e stop function per IEC 61800-5-2, removing a safety relay or a separate safety module from the panel for the torque-off channel. For a commissioning engineer, this reduces the wiring check: the STO input is a fail-safe 24 V DC loop that must be proven before the drive enables power. The rest of the safety function (gate guarding, light curtain, E-stop button) still needs its own logic, but the drive's STO covers the motor disable. No external contactor is required for that one function, though for full isolation during maintenance a line-side contactor is still standard practice.