The Siemens 3RU2126-1KB0 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, phase asymmetry, and prolonged overcurrent operation. Designed for industrial motor control applications, 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 motor starter assemblies and automation systems.
The relay operates using Siemens' proven thermal overload protection technology, continuously monitoring motor current and disconnecting 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 provides enhanced motor protection and operational reliability.
The Variant KB0 offers an adjustable overload release setting of 5.5–8 A, making it suitable for protecting motors used in pumps, compressors, conveyor systems, fans, HVAC equipment, machine tools, packaging machinery, and industrial automation installations. The relay is designed for direct mounting onto Siemens S0 contactors, enabling compact and efficient motor starter configurations.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2126-1KB0 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 3RU2126-1KB0 delivers dependable long-term performance in demanding industrial environments where continuous motor protection is essential.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2126-1KB0 |
| SKU | 3RU2126-1KB0 |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | KB0 |
| 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 Contacts | 1 NO + 1 NC |
| Reset Type | Manual / Automatic |
| Rated Operational Voltage | Up to 690 V AC |
| Operating Frequency | 50/60 Hz |
| Number of Main Poles | 3 |
| Protection Features | Overload, Phase Failure & Phase Asymmetry Protection |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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