The Siemens 3RU2126-1CB0 is a compact and 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 excessive current draw. Featuring an adjustable current setting range of 1.8–2.5 A, Class 10 tripping characteristics, and compatibility with Size S0 Siemens contactors, this relay is ideally suited for industrial motor control systems, automation equipment, and compact motor starter assemblies. Siemens SIRIUS 3RU2 relays are designed for current-dependent motor protection and direct contactor mounting applications.
The relay operates using Siemens' proven inverse-time thermal tripping technology, continuously monitoring motor current and disconnecting the motor when overload conditions persist beyond permissible limits. This protection mechanism helps prevent motor overheating, insulation damage, and costly downtime while allowing normal motor starting currents. Integrated phase-failure sensitivity further enhances motor protection and operational reliability.
The Variant CB0 offers an adjustable overload release setting of 1.8–2.5 A, making it suitable for protecting small three-phase motors used in pumps, fans, conveyors, compressors, HVAC systems, packaging machinery, machine tools, and industrial automation applications. Its compact S0 frame size allows efficient integration into motor control centers (MCCs), OEM machinery, switchboards, and industrial control panels.
The relay is designed for direct contactor mounting and includes 1 Normally Open (NO) and 1 Normally Closed (NC) auxiliary contact for signaling, trip indication, and control circuit integration. It supports both manual and automatic reset modes and features screw-type terminals for secure wiring and simplified installation.
Manufactured according to Siemens' stringent quality standards, the 3RU2126-1CB0 delivers dependable long-term performance in demanding industrial environments where continuous motor protection is essential.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2126-1CB0 |
| SKU | 3RU2126-1CB0 |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | CB0 |
| Current Setting Range | 1.8–2.5 A |
| Relay Size | S0 |
| Trip Class | Class 10 |
| Mounting Type | Direct Contactor Mounting |
| Operating Principle | Thermal |
| Main Circuit Connection | Screw Terminal |
| Auxiliary Circuit Connection | Screw Terminal |
| Auxiliary Contacts | 1 NO + 1 NC |
| Reset Type | Manual / Automatic |
| Rated Insulation Voltage | Up to 690 V AC |
| Number of Main Poles | 3 |
| Protection Features | Overload & Phase Failure Protection |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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