Siemens SIRIUS 3RT1326-1BW40 — S0 Power Contactor, 4 NO, 11 kW AC-2
The Siemens 3RT1326-1BW40 is a SIRIUS-brand power contactor in the S0 frame size, carrying four normally-open main contacts and rated for 11 kW at AC-2 duty on 400 V — that's the motor-switching curve for slip-ring or wound-rotor motors, not the lighter AC-3 squirrel-cage load.
If you're switching a standard squirrel-cage motor, AC-3 is the usual duty class — this contactor's AC-3 rating isn't listed, so treat the AC-2 number as the ceiling for any inductive motor load. The 4 NO main contacts mean you get four independent power poles, which lets you switch a three-phase motor plus a neutral or a second load without adding a separate contactor block. For coordination, type 1 requires a 63 A gL/gG fuse upstream; type 2 needs a 35 A gL/gG — that's the fuse that limits let-through energy to protect the contactor during a bolted fault. The IP20 front and IP00 terminals mean the wiring area is live when the panel door is open — standard for enclosed gear, but worth flagging for anyone doing live troubleshooting.
The S0 frame measures 61 mm wide, 85 mm tall, and 101 mm deep — that's the body without terminals. The screw terminals for the main circuit accept 2x (1 to 2.5 mm²) stranded or 2x (2.5 to 6 mm²) and up to 2x 10 mm² — that's good for the 35 A fuse link in a type 2 scheme. The coil draws 5.4 W holding and 5.4 W closing at DC, so it's a constant-hold coil — no power dip on pickup, which simplifies the DC supply sizing.