The Siemens 3RA1145-4JB44-1BP4 is a SIRIUS non-fused motor starter — a direct starter assembly combining a contactor and a thermal bimetallic overload relay in one S3-size package.
For those, you'd want CLASS 20 or 30. The bimetallic design is field-adjustable and self-powered, so no auxiliary supply is needed for the overload function. At 460/480 V it's rated 50 hp, and at 575/600 V it's rated 60 hp — that's the motor horsepower it can switch in AC-3 duty. The control voltage is fixed at 230 V — the coil is 230 V AC, so make sure your control transformer or PLC output matches that. It's a direct starter, meaning the contactor and overload are wired in series with no reversing or reduced-voltage logic built in. That's the most common configuration for fixed-speed pumps, fans, and conveyors.
Snaps onto 35 mm standard rail, mounted vertically. No clearance needed backwards — it sits flush against the panel backplate. That matters when you're laying out a crowded enclosure: you can butt it against the back wall.