SIRIUS S3 power contactor — what the ratings mean for fit
The Siemens 3RT1045-3BM40 is a SIRIUS S3-frame power contactor, designated for switching motor loads in industrial control panels. Its headline motor rating is 45 kW at 500 V (AC-3 duty,), which means it directly switches a three-phase induction motor of that size in a standard pump, fan, or conveyor application — no external bypass contactor needed. The AC-4 rating of 66 A at 400 V governs plugging and inching duty: if the load requires frequent reversal or jogging, this is the current limit that determines thermal stress on the contacts, not the AC-3 figure. Screw-type terminals on the main circuit accept stranded conductors up to 2x 50 mm² and solid up to 2x 2.5 mm², covering the full range from control wiring to motor feeders. The IP20 front face with cover/box terminal means the panel builder can leave the front exposed for troubleshooting — the IP00 terminal body is protected once enclosed in the panel, which is standard for DIN-rail mounted gear.
Mounting and integration — DIN rail and side-by-side
Snaps onto standard 35 mm or 75 mm mounting rail, and side-by-side mounting is permitted — no mandatory spacing between units, which keeps the panel row dense. The S3 frame measures 70 mm wide by 146 mm tall by 152 mm deep, so a row of three fits in under 210 mm of DIN-rail width. Pollution degree 3 means the contactor is rated for conductive pollution typical in industrial enclosures — no conformal coating required for normal panel environments. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C.
Switching frequency and mechanical life
Maximum mechanical switching frequency is 10,000,000 operations typical. The electrical switching frequency depends on duty: 1,000 operations per hour in AC-3, 900 in AC-1 resistive, 400 in AC-2, and 300 in AC-4. For a conveyor running at 30 cycles per hour, the AC-3 rating leaves headroom; for a press with frequent jogging at 150 cycles per hour, the AC-4 limit of 300 ops/h still fits but the contact wear will be higher — plan spares accordingly. DC switching ratings are given for the auxiliary circuit: 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V — these govern the control-side contacts, not the main poles.
Lifecycle and compliance
The lifecycle stage is marked as current — this part remains in the active Siemens SIRIUS portfolio. No phase-out or last-time-buy notice is attached to this order code. The substance prohibition date of 05/01/2012 aligns with the original RoHS compliance cutoff; expect the current production to meet RoHS and REACH requirements. The contactor carries a rated insulation voltage of 690 V (implied by the 690 V motor rating of 21.1 kW,) and a rated impulse withstand voltage consistent with the SIRIUS family. Compliance documentation (CE, UL, CSA) is standard for the SIRIUS line — confirm the specific UL file number with the order if a panel UL 508A listing requires it.