The SENTRON 5SM2633-0 is a residual current unit (RC unit) designed to pair with the 5SL4 miniature circuit breaker. It's a 3-pole, type AC device rated at 40 A with a 300 mA tripping fault current, operating at 230/400 V and 50 Hz.
The 40 A rated operational current is the continuous load this unit can handle at its reference temperature. But if your panel runs hot — and out here in the grease, they often do — you need to follow the derating curve: at 50 °C it's still good for 36 A, at 60 °C it drops to 34 A, and at 70 °C you're down to 32 A. That's the real-world number for a crowded enclosure. The 300 mA residual trip threshold is for equipment protection or fire prevention, not personnel shock protection — that's what the 30 mA class handles. The instantaneous design (no short-time delay) means it trips fast on a ground fault, which is fine for most general-purpose circuits.
Width is 105 mm, height is 90 mm. That flexibility matters when you're squeezing it into an existing panel layout. The silicon-free marking is useful if you're in a potting or coating environment where silicone contamination is a concern.