Siemens 3RT5045 – SIRIUS Contactor for Heavy‑Duty Load Switching

The Siemens 3RT5045 series belongs to the SIRIUS family of industrial contactors, designed for reliable switching of motors, resistive loads, and capacitor banks in automation and power distribution systems. This particular model is available with several coil voltage variants, including 3RT5045‑1BB40, 1BF40, 1AC20, 1AG00, 1AG20, 1AN20, and 1AQ00, each catering to different control circuit requirements.

Rated Electrical Characteristics

The 3RT5045 contactor is rated for AC‑3 duty (squirrel‑cage motor starting) with a maximum operational current of 65 A at 400 V AC. The rated insulation voltage is 1000 V, and the rated impulse withstand voltage is 8 kV, ensuring robust insulation coordination. The contactor can withstand short‑circuit currents up to 10 kA when protected by appropriate fuses or circuit breakers.

Coil Variants and Control Voltages

The various suffix codes denote different coil voltages:

• 1BB40 – 24 V AC/DC (bimetal coil)

• 1BF40 – 110 V AC (50/60 Hz)

• 1AC20 – 220‑240 V AC

• 1AG00 – 380‑400 V AC

• 1AG20 – 440 V AC

• 1AN20 – 550 V AC

• 1AQ00 – 690 V AC

All coils are equipped with built‑in transient suppression (varistor) to reduce electromagnetic interference during switching. The coil consumption is approximately 20 VA during closing and 6 VA during holding, making them energy‑efficient.

Contact Configuration

The contactor features three main poles (3‑pole) with normally open contacts, plus one normally open and one normally closed auxiliary contact as standard. Additional auxiliary contact blocks can be snapped on for up to four more contacts, offering flexibility for interlocking and status feedback. The contacts are made of silver‑tin oxide alloy, providing excellent weld resistance and long electrical life.

Mechanical and Electrical Durability

Mechanical endurance exceeds 10 million operations, while electrical endurance under AC‑3 duty is rated at 1.2 million operations. The contactor is designed for frequent switching, with a maximum operating frequency of 600 cycles per hour. The finger‑safe terminals ensure safe wiring, and the unit is designed for screw or snap‑on mounting on DIN rails.

Environmental Ratings

Operating temperature range is -25 °C to +60 °C, with storage down to -55 °C. The contactor is protected to IP20 (finger‑safe) and can be mounted in any position. It is certified to CE, cURus, and CCC standards, and complies with RoHS and REACH directives.

Protection and Accessories

The contactor can be combined with overload relays (e.g., 3RB series) for motor protection, as well as with mechanical interlocks for reversing applications. Surge suppressors and RC snubbers are available as add‑on modules. The unit is compatible with Siemens’ SIRIUS modular system, allowing easy integration with starters and control panels.

Applications

Typical uses include motor starters, heating elements, lighting control, transformer switching, and capacitor bank control in industrial plants, building automation, and HVAC systems.

Installation and Maintenance

Wiring diagrams are printed on the side of the contactor for quick reference. Regular inspection of contact wear and coil resistance is recommended, but the unit is maintenance‑free under normal conditions. Spare parts and replacement coils are readily available from Siemens distributors.

In summary, the Siemens 3RT5045 contactor series offers a versatile, high‑performance switching solution with multiple coil voltage options to match a wide range of control applications.