Siemens 3RW4047-1BB14 SIRIUS 3RW40 Soft Starter for 55kW Motor Control

Product Overview

The Siemens 3RW4047-1BB14 is a soft starter from the SIRIUS 3RW40 series, designed for three-phase induction motors up to 55 kW at 400 V. It provides smooth acceleration and deceleration, reducing mechanical stress on the driven load and limiting inrush current to the electrical supply. The device integrates a bypass contactor to short-circuit the thyristors after starting, minimizing heat dissipation and eliminating the need for external bypass. This soft starter is suitable for applications such as pumps, fans, compressors, and conveyors.

Key Features of 3RW4047-1BB14

The soft starter has a rated operational current of 65 A (at 40°C) for normal-duty applications. It features adjustable start voltage, start ramp time (1-20 sec), stop ramp time (0-20 sec), and current limiting (150-500% of motor current). The integrated bypass reduces power loss and allows for compact cabinet mounting. The device includes thermal overload protection for the motor (class 10, 20, 30 selectable) and a PTC thermistor input. It has a 24 V DC control supply (standard).

The 3RW4047-1BB14 has a 24 V DC logic input for start/stop, and relay outputs for running and fault indication. It is rated for a continuous operating temperature of -25 to +60°C (derating above 40°C). The unit has screw terminals for main connections and is designed for DIN rail or panel mounting. It complies with IEC 60947-4-2 and UL 508. The soft starter includes diagnostic LEDs for power, run, and fault status.

Technical Specifications

• Manufacturer: Siemens AG

• Part Number: 3RW4047-1BB14

• Series: SIRIUS 3RW40

• Product Type: Soft Starter

• Rated Power: 55 kW at 400 V AC (normal-duty)

• Rated Current (Ie): 65 A (40°C)

• Start Modes: Voltage ramp, current limiting

• Stop Modes: Soft stop, freewheel

• Integrated Bypass: Yes

• Control Supply Voltage: 24 V DC (±10%)

• Digital Inputs: 2 (start/stop, reset)

• Digital Outputs: 2 relays (run, fault)

• Motor Protection: Electronic overload (class 10/20/30)

• Operating Temperature: -25 to +60 °C

• Degree of Protection: IP20

• Dimensions (W x H x D): 75 mm x 200 mm x 180 mm (approx.)

• Certifications: CE, UL, CSA, CCC

Functional Description

When a start command is given, the thyristors begin conducting with a small firing angle, producing reduced voltage. Over the programmed start ramp time, the voltage increases until full conduction is reached; then the integrated bypass contactor closes, shorting the thyristors. During stopping, the bypass opens and a voltage ramp-down can be applied. The electronic overload protects the motor by calculating thermal capacity. The PTC input can monitor motor temperature directly.

Applications

This soft starter is used for centrifugal pumps (to prevent water hammer), fans (reduce belt stress), compressors, and conveyor belts. It is a replacement part for existing 3RW40 starters.