3RW4456-6BC44 780A SIRIUS Soft Starter

Introduction to the Siemens 3RW4456-6BC44 Soft Starter

When motor starting demands precise control and high reliability, the 3RW4456-6BC44 from Siemens SIRIUS series provides a robust solution. This soft starter is designed for three-phase motors and offers a rated operational current of 780 A at 400 V, 40 °C in standard circuit. For inside-delta configurations, it handles up to 1351 A, making it suitable for demanding industrial applications.

As part of the SIRIUS family, this device integrates essential protective functions, including motor overload protection and thermistor evaluation. Its phased-out status means users should consider the successor model 3RW5554-6HA14, but the 3RW4456-6BC44 remains a capable option for existing installations.

Key Features and Technical Specifications

The 3RW4456-6BC44 is engineered for performance and safety. Below are the core specifications extracted from the datasheet:

• Rated operational current: 780 A at 40 °C (standard circuit), 693 A at 50 °C, 615 A at 60 °C
• Inside-delta current: 1351 A at 40 °C, 1200 A at 50 °C, 1065 A at 60 °C
• Rated operational voltage: 200–460 V AC (standard and inside-delta circuits)
• Control supply voltage: 230 V AC at 50/60 Hz
• Operating frequency: 50–60 Hz (±10% tolerance)
• Insulation voltage: 690 V
• Degree of pollution: 3 (according to IEC 60947-4-2)
• Integrated bypass contact system: Yes
• Motor overload protection: Yes
• Adjustable current limitation: Yes
• Inside-delta circuit support: Yes

One distinctive feature is the integrated bypass contact system, which reduces heat dissipation during continuous operation, improving energy efficiency and extending component life.

Applications and Use Cases

This soft starter is ideal for conveyors, pumps, fans, and compressors where controlled acceleration reduces mechanical stress. In inside-delta wiring, it can start motors up to 800 kW at 400 V, making it suitable for high-inertia loads. Its wide voltage range (200–460 V) allows deployment across various global power systems.

Installation and Mounting

The 3RW4456-6BC44 features screw fixing and can be mounted vertically with ±90° rotation or tilted up to ±22.5°. Required clearances are 100 mm upward, 5 mm sideways, and 75 mm downward for proper ventilation. Main circuit connections use busbar connections, while auxiliary and control circuits use screw terminals. Connectable conductor cross-sections range from 50 to 240 mm² for main contacts.

Maintenance and Reliability

Thanks to the integrated bypass, the thyristors are bypassed after starting, reducing thermal stress and extending service life. Periodic inspection of terminal tightness and ambient temperature is recommended. The device operates at ambient temperatures up to 60 °C, with derating above 40 °C. For safety, always follow the manufacturer's manual for maintenance procedures.

Compatibility and Integration

The soft starter supports both standard and inside-delta circuits, offering flexibility in motor connection. It includes three NO contacts and one CO contact for auxiliary signaling, enabling integration with PLCs or control panels. The control supply accepts 230 V AC at 50/60 Hz, simplifying wiring in industrial environments.

Troubleshooting and Common Issues

If the motor fails to start, verify the control supply voltage and frequency. Overload trips can occur if the motor current exceeds the adjustable setting—check the motor nameplate and adjust the overload relay accordingly. For thermistor faults, ensure the motor PTC sensor is correctly connected. If issues persist, consult the official Siemens documentation or contact AutoDCSTech.

Product Support and Availability

Although the 3RW4456-6BC44 is phased out, AutoDCSTech may have stock or can assist with the successor model. Contact our team to verify current availability and lifecycle status before ordering.