The Siemens 3RU2126-1FB0 is a high-performance thermal overload relay from the trusted SIRIUS 3RU2 Series, engineered to provide reliable protection for three-phase motors against overload conditions, phase failure, and prolonged overcurrent operation. The relay features an adjustable current setting range of 3.5–5 A, Class 10 tripping characteristics, and compatibility with Size S0 Siemens contactors, making it ideal for industrial motor control systems, motor starter assemblies, and automation applications.
Built on Siemens' proven thermal overload protection technology, the relay continuously monitors motor current and disconnects the motor when overload conditions persist. Its inverse-time delayed tripping characteristic helps prevent motor overheating, insulation damage, and premature motor failure while allowing normal motor starting currents. Integrated phase-failure sensitivity enhances motor protection and operational reliability.
The Variant FB0 offers an adjustable overload release setting of 3.5–5 A, making it suitable for protecting motors used in pumps, fans, compressors, conveyor systems, HVAC equipment, packaging machinery, machine tools, and industrial automation installations. Its compact S0 frame size allows efficient integration into motor starter assemblies, MCC panels, OEM equipment, and control cabinets.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2126-1FB0 supports both manual and automatic reset modes and includes 1 Normally Open (NO) and 1 Normally Closed (NC) auxiliary contacts for signaling, monitoring, and control circuit integration. Screw-type terminals ensure secure electrical connections and simplified installation. The relay is designed for operating voltages up to 690 V AC.
Manufactured according to Siemens' stringent quality standards, the 3RU2126-1FB0 delivers dependable long-term performance in demanding industrial environments where continuous motor protection is essential.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2126-1FB0 |
| SKU | 3RU2126-1FB0 |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | FB0 |
| Current Setting Range | 3.5–5 A |
| Relay Size | S0 |
| Trip Class | Class 10 |
| Operating Principle | Thermal |
| Mounting Type | Direct Contactor Mounting |
| Main Circuit Connection | Screw Terminal |
| Auxiliary Contacts | 1 NO + 1 NC |
| Reset Type | Manual / Automatic |
| Rated Insulation Voltage | 690 V |
| Surge Voltage Resistance | 6 kV |
| Operating Frequency | 50/60 Hz |
| Number of Main Poles | 3 |
| Operating Temperature | -40°C to +70°C |
| Protection Features | Overload & Phase Failure Protection |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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