Description
The 3RT5046-1BB40 is a Siemens SIRIUS 3RT5 series 3-pole power contactor with a DC 24 V control coil, belonging to the S3 frame size. Rated at 95 A (AC-1) / 45 kW at 400 V (AC-3), it is engineered for frequent switching of three-phase motors, pumps, compressors, and resistive loads where a PLC transistor output is the preferred coil driver. The S3 footprint keeps the width at just 45 mm while delivering heavy-current performance, making it a staple in compact OEM panels and retrofit MCC buckets.
Application Scenarios
A German HVAC OEM was redesigning a 22-kW condenser-fan panel that had to fit inside a rooftop unit already crowded with VFDs, filters, and a compact S7-1200. The legacy design used AC 230 V contactors, each gated through a 24 V → 230 V interposing relay so the PLC could drive them — eight relays per panel, eight extra failure points, and a noticeable hum on hot days when coil buzz drifted into the building management system’s acoustic sensor. The redesign swapped to the 3RT5046-1BB40: DC 24 V coil, built-in flyback diode, screw terminals, S3 frame. The PLC’s 24 V DC transistor outputs now drove the contactor coils directly — eight interposing relays gone, panel width dropped by one 18-mm slice, and the DC coil ran silent compared to the old AC units. Commissioning reported zero nuisance dropouts during the compressor in-rush current spike, because the 3RT5046-1BB40 holds firm at 0.8 × Us even under voltage sag. For a rooftop fleet of 140 units, that translated to ~€4,200 BOM saving per panel plus a measurable MTBF bump.
Parameter
| Main Parameters | Value/Description |
|---|---|
| Product Model | 3RT5046-1BB40 |
| Manufacturer | Siemens (SIRIUS 3RT5 Series) |
| Product Category | 3-Pole Power Contactor (DC Coil) |
| Size / Frame | S3 (45 mm width) |
| Rated Current (AC-1) | 95 A |
| Motor Rating (AC-3, 400 V) | 45 kW |
| Coil Voltage | DC 24 V (built-in flyback diode) |
| Main Contacts / Aux. | 3 NO / none integrated (S3: expandable to +8) |
| Mechanical Life | ≥ 10 million cycles |
| Electrical Life (AC-3) | ≥ 1 million cycles |
| Mounting | 35 mm DIN rail or screw-fix |
| Protection / Temp. | IP20 / –25 °C to +60 °C |
| Standards | IEC 60947-4-1, UL 508, CCC/CE/UL/CSA |
Technical Principles and Innovative Values
- Innovation Point 1: DC 24 V coil with integrated flyback diode. The 3RT5046-1BB40 is optimized for direct drive from PLC transistor outputs (S7-1200/1500, ET 200, etc.) without an interposing relay. The onboard free-wheeling diode clamps the turn-off spike that would otherwise hammer the PLC output stage — a detail that saves both BOM cost and long-term reliability headaches.
- Innovation Point 2: S3 “density” packaging. Most 95 A contactors sit in 55–70 mm wide bodies. The 3RT5046-1BB40 squeezes the same 45 kW rating into 45 mm by using SIRIUS S3’s compact magnetic path and screw-terminal layout. In an MCC section with 12 starters side-by-side, that’s 120–300 mm reclaimed — often the difference between a 800 mm and a 600 mm enclosure.
- Innovation Point 3: Tool-free accessory ecosystem. S3 frames accept up to 8 additional auxiliary contacts, mechanical interlocks, RC suppressors, and phase busbars — all snap-on with no tools. The 3RT5046-1BB40 itself carries no built-in aux (S3 characteristic), but the side-mount blocks click on after wiring is done, so you can spec “aux later” without reopening the terminal screws.
