The Siemens 3RU2126-1KB00-8K is a reliable thermal overload relay from the trusted SIRIUS 3RU2 Series, designed to provide effective protection for three-phase motors against overload conditions, phase failure, and prolonged overcurrent operation. This relay features an adjustable current setting range of 5.5–8 A, Class 10 tripping characteristics, and compatibility with Size S0 Siemens contactors, making it ideal for industrial motor control and protection applications. The 3RU2 series is designed for direct contactor mounting and dependable motor protection in automation systems.
The relay operates using Siemens' proven inverse-time thermal tripping technology, continuously monitoring motor current and disconnecting the motor when overload conditions persist. This protection mechanism helps prevent motor overheating, insulation damage, and costly downtime while allowing normal motor starting currents. The relay also incorporates phase-failure sensitivity for enhanced motor protection.
The Variant KB008K provides an adjustable overload release setting of 5.5–8 A, making it suitable for protecting motors used in pumps, fans, compressors, conveyors, packaging equipment, machine tools, HVAC systems, and general industrial machinery. Its compact S0 frame size enables efficient integration into motor starter assemblies and control panels.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2126-1KB00-8K supports both manual and automatic reset modes and includes 1 Normally Open (NO) and 1 Normally Closed (NC) auxiliary contact for signaling, monitoring, and control circuit integration. Screw-type terminals ensure secure electrical connections and simplified installation.
Manufactured according to Siemens' stringent quality standards, the 3RU2126-1KB00-8K delivers dependable long-term performance in demanding industrial environments where continuous motor protection is essential.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2126-1KB00-8K |
| SKU | 3RU2126-1KB00-8K |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | KB008K |
| Current Setting Range | 5.5–8 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 |
| Number of Main Poles | 3 |
| Protection Features | Overload & Phase Failure Protection |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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