Siemens 3RW4458-6BC44 Soft Starter 970A 560kW

3RW4458-6BC44 Siemens SIRIUS Soft Starter – High-Current Motor Control

Product Introduction

This section examines the Siemens 3RW4458-6BC44 soft starter in detail. It belongs to the well-known SIRIUS product family. Engineers choose this model for demanding motor starting applications. The unit delivers a 970A operational current at 40°C in standard mode. For inside-delta circuits, the rating jumps to 1680A. This flexibility makes the 3RW4458-6BC44 suitable for pumps, fans, and compressors.

Please be aware that Siemens has phased out this product. The official successor is the SIRIUS 3RW5 series, specifically 3RW5556-6HA14. However, many existing systems still require the 3RW4458-6BC44 for direct replacement. Therefore, we offer this model for maintenance and retrofit projects.

Core Technical Specifications

The Siemens 3RW4458-6BC44 operates at a rated insulation voltage of 690V. It includes an integrated bypass contact system and thyristors. Several protective functions come standard. For instance, you get motor overload protection and thermistor motor protection evaluation. An external reset and adjustable current limitation add more control.

Operational Current Values by Temperature:

• At 40°C (standard): 970A

• At 50°C (standard): 850A

• At 60°C (standard): 760A

• At 40°C (inside-delta): 1680A

• At 50°C (inside-delta): 1472A

• At 60°C (inside-delta): 1316A

Motor Power Output at 400V and 40°C:

• Standard circuit: 560kW

• Inside-delta circuit: 1000kW

For 230V applications at 40°C, the 3RW4458-6BC44 provides 315kW in standard mode. Inside-delta wiring increases this to 560kW. The operating voltage range spans 200 to 460V AC with a tolerance of -15% to +10%. Control supply voltage is fixed at 230V AC for both 50Hz and 60Hz systems.

Protection Features and Control Functions

This soft starter offers comprehensive device protection. The integrated bypass reduces heat generation after starting. Additionally, a motor brake output is included for dynamic braking applications. The device supports external reset for remote operation.

Auxiliary Contact Configuration:

• Number of NO contacts: 3

• Number of CO contacts: 1

• Number of NC contacts: 0

A display provides clear fault signalling. The adjustable current limitation helps manage inrush currents effectively. Furthermore, the minimum load requirement is only 8% of the rated current. The adjustable motor overload protection starts from 194A.

Power Loss and Load Capacity

At 40°C with rated current, typical power loss is 270W. The continuous operating current can sustain 115% of Ie at 40°C. This overhead allows for temporary overload conditions without immediate tripping. Such a margin proves valuable for high-inertia loads.

Mechanical Dimensions and Installation

Physical Dimensions:

• Width: 510 mm

• Height: 640 mm

• Depth: 290 mm

Mounting Requirements:

The Siemens 3RW4458-6BC44 uses screw fixing for installation. You can rotate the unit +/-90° on a vertical surface. Tilting is also possible up to +/-22.5° forward or backward. For side-by-side mounting, follow these spacing rules:

• Upwards clearance: 100 mm

• Side clearance: 5 mm

• Downwards clearance: 75 mm

Maximum wire length from the starter to the motor is 500 meters. The main current circuit uses three poles.

Terminal and Wiring Specifications

Main current connections use busbar terminals. Auxiliary and control circuits connect via screw-type terminals.

Conductor Sizes for Main Contacts (DIN cable lug):

• Finely stranded: 50 to 240 mm²

• Stranded: 70 to 240 mm²

Conductor Sizes for Auxiliary Contacts:

• Solid wires: 2x (0.5 to 2.5 mm²)

• Finely stranded with core end processing: 2x (0.5 to 1.5 mm²)

AWG equivalents:

• Main contacts: 2/0 to 500 kcmil

• Auxiliary contacts: 2x (20 to 14)

• Auxiliary finely stranded: 2x (20 to 16)

Environmental Conditions and Derating

The 3RW4458-6BC44 operates reliably in various environments. Maximum installation altitude is 5000 meters above sea level. Operating ambient temperature reaches up to 60°C. However, derating begins at 40°C. Storage temperature ranges from -25°C to +80°C.

Environmental Categories per IEC 60721:

• Transport: 2K2, 2C1, 2S1, 2M2 (max fall 0.3m)

• Storage: 1K6, 1C2, 1S2, 1M4

• Operation: 3K6, 3C3, 3S2, 3M6

Front protection class is IP00 according to IEC 60529. Pollution degree rating is 3, following IEC 60947-4-2.

Frequently Asked Questions (FAQ)

1. Is the Siemens 3RW4458-6BC44 still available for purchase?

This model is phased out by Siemens. However, we maintain stock of new old stock and refurbished units. For brand new installations, Siemens recommends the successor 3RW5556-6HA14.

2. What is the maximum power output for this soft starter?

At 400V and 40°C, the 3RW4458-6BC44 delivers 560kW in standard circuit. With inside-delta connection, it reaches 1000kW. This makes it suitable for very large motors.

3. Can I use this unit with a 230V control supply?

Yes, the control circuit requires 230V AC. It works for both 50Hz and 60Hz systems. The acceptable tolerance is -15% to +10%.

4. What cooling clearances does this soft starter need?

You must maintain specific spacing for proper airflow. Leave 100mm above the unit. Allow 5mm on each side. Keep 75mm clearance below the unit. Failure to do so may cause overheating.

5. Does the 3RW4458-6BC44 include an integrated bypass?

Yes, it does. The integrated bypass contact system engages after starting. This reduces power loss to only 270W during continuous operation. It also extends the life of the thyristors.