Drive selection memo — 6SL3210-1KE21-7UP0
The Siemens 6SL3210-1KE21-7UP0 is a SINAMICS G120C variable-frequency drive rated for 7.5 kW output on a 380-480 VAC three-phase supply, with a 150% overload capability for 3 seconds — enough headroom for short-duration load spikes like conveyor startups or pump breakaway torque. It carries integrated Safe-Torque-Off (STO), so it can serve in safety circuits up to SIL 3 / PL e without an external safety relay, and the onboard PROFIBUS DP fieldbus means it drops into a Siemens S7-300/400 or third-party master network without an additional communication module. The I/O complement — 6 digital inputs, 2 digital outputs, 1 analog input, 1 analog output — covers basic speed reference and feedback for a single motor; for multi-axis or encoder feedback, you'd add a terminal module.
Panel fit and mounting
The drive is IP20 / UL Open Type, so it belongs in a clean, dry enclosure — not on the machine frame in a washdown zone. The FSB (Frame Size B) footprint is 196 x 100 x 203 mm (HxWxD), which fits a standard 200 mm deep backpanel with clearance for top/bottom cable glands.
Lifecycle and sourcing reality
For a BOM freeze or a long-term project, the G120C series is stable; the PROFIBUS variant is less common than the PROFINET version, so if your network is migrating to PROFINET, consider the 6SL3210-1KE21-7UP1 or -7UP2 as a future-proof drop-in (same frame, same wiring).
What the ratings mean for your application
The 7.5 kW rating at 380-480 VAC is the continuous motor shaft power under normal duty (IEC 61800-2 class 1). The 150% overload for 3 seconds means the drive can deliver 11.25 kW for brief transients — enough to clear a jammed conveyor or start a loaded compressor, but not for repeated cycling (that would need a higher frame size or external braking resistor). The unfiltered input (no built-in EMC filter) means you must add an external line filter if the drive is installed in a residential or light-industrial environment (first environment per IEC 61800-3). In a factory with a dedicated transformer, the unfiltered drive is fine and saves panel space. The 47-63 Hz input frequency range covers both 50 Hz and 60 Hz grids globally — no jumper change needed when shipping a machine from Europe to North America.