The Siemens 3RU2126-4PB0 is a high-performance thermal overload relay from the trusted SIRIUS 3RU2 Series, designed to provide reliable protection for three-phase motors against overload conditions, phase failure, and excessive current draw. The relay features an adjustable current setting range of 30–36 A, Class 10 tripping characteristics, and is designed for direct mounting on Siemens Size S0 contactors, making it ideal for industrial motor control and protection 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 overheating, insulation damage, and premature motor failure while allowing normal motor starting currents. The relay also incorporates phase-failure sensitivity for enhanced motor protection and operational reliability.
The Variant PB0 provides an adjustable overload release setting of 30–36 A, making it suitable for protecting motors used in pumps, compressors, conveyor systems, fans, HVAC equipment, machine tools, packaging machinery, and industrial automation installations. Its compact S0 frame design enables efficient integration into motor starter assemblies and control panels.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2126-4PB0 supports both manual and automatic reset modes and includes 1 Normally Open (NO) and 1 Normally Closed (NC) auxiliary contact for trip indication, signaling, and control circuit integration. The relay uses screw-type terminals for secure electrical connections and simplified installation.
With a rated insulation voltage of 690 V, surge voltage resistance of 6 kV, operating temperature range of -40°C to +70°C, and a compact S0 construction, the relay delivers dependable long-term performance in demanding industrial environments.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2126-4PB0 |
| SKU | 3RU2126-4PB0 |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | PB0 |
| Current Setting Range | 30–36 A |
| Relay Size | S0 |
| Trip Class | Class 10 |
| Operating Principle | Thermal |
| Mounting Type | Direct Contactor Mounting |
| Main Circuit Connection | Screw Terminal |
| Auxiliary 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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