The Siemens 6SL3203-0BB21-8VA0 is a spare-part EMC filter for the SINAMICS V90 servo drive family, rated 200-240 V 1-phase AC at 18 A, 50/60 Hz. It's the line-side noise suppression stage for a single-phase V90 drive in that voltage class — sized to the drive's input current, not the motor's. The 59x155x53 mm (WxHxD) footprint matches the V90 drive frame; it mounts between the line supply and the drive's power input terminals.
What the 18 A rating governs
The 18 A figure is the filter's rated continuous current at 200-240 V single-phase AC. That's the drive's input current, not the motor FLA — so a 400 W or 750 W V90 servo on single-phase supply typically draws well under this. Oversizing a filter doesn't hurt noise suppression, but the mechanical fit (59x155x53 mm) is fixed; a larger filter won't bolt to the same drive frame. If your BOM calls for this exact order code, the 18 A rating confirms it handles the drive's full input without derating at 50/60 Hz line frequency.