SIRIUS S3 power contactor — what it handles and where it fits
The Siemens SIRIUS 3RT1046-3BF40 is a size S3 power contactor rated for motor switching up to 55 kW at 500 V in AC-3 duty and 80 A in AC-4 at 400 V for reversing or inching applications. The front carries IP20 protection with a cover or box terminal; the main-circuit terminals themselves are IP00 — fine inside an enclosure, not for open-panel washdown.
AC-3 at 400 V: 45 kW — that's the standard motor-switching rating for a 4-pole induction motor on a 400 V line, so it covers most 45 kW pumps, fans, and compressors in European-voltage plants. At 690 V the motor rating drops to 25.4 kW (AC-3), which is typical for high-voltage low-current loads.
Terminals and wiring
Main-circuit terminals are screw-type, accepting 2x solid conductors from 0.25 to 2.5 mm² on the control side and 2x stranded from 10 to 50 mm² on the power side. The auxiliary/coil terminals also take 2x solid 0.25–2.5 mm². That range covers standard panel wire up to 50 mm² for the main feed — no need for pin terminals or bootlace ferrules if you're using stranded.