Siemens Overload relay for motor protection, size S0, 34-40A

Product Overview

The 3RU2126-4FB0 thermal overload relay is designed for current-dependent protection of three-phase motors and electrical loads against overload, phase asymmetry, and phase failure. This Size S0, Class 10 relay features an adjustable current range of 34 to 40 A and is optimized for direct mounting on Siemens 3RT2 size 0 contactors (9 to 38 AMPS) to provide reliable motor protection for the highest current applications in the S0 series.

Key Features

• Current Range: 34 to 40 A adjustment range
• Protection Class: Class 10 tripping characteristic for fast response
• Size: S0 for larger motor applications
• Mounting: Contactor mounting, compatible with 3RT2 size 0 contactors (9-38A)
• Terminal Type: Screw terminals for both main and auxiliary circuits
• Auxiliary Contacts: 1 normally open (NO) + 1 normally closed (NC) contact
• Reset Function: Manual or automatic reset capability
• Phase Loss Protection: Built-in phase loss sensitivity
• Enclosure Rating: IP20 for standard industrial applications
• Operating Temperature: -20°C to +70°C
• Dimensions: 85mm H x 45mm W x 85mm D
• Weight: 0.200 kg

Technical Specifications

• Frequency Rating: 50/60 Hz
• Contact Rating: 40A at 690VAC
• Poles: 3-pole configuration
• Tripping Time: Less than 10 seconds at overload conditions
• Compliance: UL rated, RoHS compliant, meets IEC standards
• Maximum Operating Voltage: 690V
• Power Rating: 18.5 kW
• Insulation Voltage: 690V
• Impulse Voltage Resistance: 6 kV
• Power Loss: 6W

Applications The 3RU2126-4FB0 is suitable for protecting motors and electrical loads in industrial applications where reliable overload protection is required for very high current motor systems. It provides inverse time-delayed protection against excessive temperature rises due to overload or phase failure, making it ideal for applications with normal starting conditions and frequency converter operations requiring the highest current protection in the Size S0 range.

Operation When an overload or phase failure occurs, the motor current rises above the set rated current. This current increase heats up the bimetal strips within the relay via heating elements, causing them to bend and trigger the auxiliary contacts through a tripping mechanism. The auxiliary contacts then switch off the load via a contactor, with the tripped status indicated by a switch position indicator. The relay features both TEST and STOP functions for enhanced functionality.

Product Information

• Net Weight: 0.200 kg
• Packaging Dimensions: 49.00 x 102.00 x 102.00 mm
• EAN: 4011209781009
• UPC: 662643919424
• Country of Origin: Germany

Compliance & Environmental

• RoHS Compliance: Yes (since 01.10.2009)
• UL Rating: Yes
• WEEE Take-Back: Yes (2012/19/EU)
• REACH Article 33: Contains lead in concentrations higher than 0.1% w/w
• Export Control: AL: N / ECCN: N
• Approvals: UL, CSA, CCC, EAC, CE, EX, IECEX

Download existing graphical data for this product:

• Product Datasheet
• Technical Documentation
• CAD Data and Drawings

Additional Resources

• SIRIUS 3RU2 Product Family
• Siemens Industry Mall