The Siemens 3RU2146-4FB0 is a high-performance thermal overload relay from the trusted SIRIUS 3RU2 Series, designed to provide dependable protection for three-phase motors against overload conditions, phase failure, and excessive current draw. The relay features an adjustable current setting range of 28–40 A, Class 10 tripping characteristics, and is designed for use with Size S3 contactors, making it suitable for demanding industrial motor control applications.
The relay operates using Siemens' proven thermal overload protection technology, continuously monitoring motor current and disconnecting the motor when overload conditions persist. This helps prevent motor overheating, insulation damage, reduced equipment life, and costly downtime while improving operational reliability. Thermal overload relays in the SIRIUS 3RU2 range provide inverse-time delayed protection and phase-failure sensitivity for comprehensive motor protection.
The Variant FB0 is designed for contactor mounting and incorporates a thermal inverse-time delayed overload release with an adjustable setting range of 28–40 A. It is ideal for protecting motors used in pumps, compressors, conveyors, fans, HVAC systems, manufacturing equipment, and industrial automation machinery.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2146-4FB0 supports both manual and automatic reset modes, allowing users to configure protection according to operational requirements and plant safety procedures. The relay includes integrated 1 NO + 1 NC auxiliary contacts for trip indication and control circuit integration.
Its compact S3 frame size allows seamless integration into motor starter assemblies, MCC panels, and industrial control systems. The relay utilizes screw-type terminals for secure electrical connections and easy installation in industrial environments.
The Class 10 trip characteristic provides rapid protection for standard motor starting applications while minimizing nuisance tripping during normal operation. The relay also incorporates phase-failure protection, helping safeguard motors against damaging single-phasing conditions.
Manufactured according to Siemens' stringent quality standards, the 3RU2146-4FB0 delivers reliable long-term performance in manufacturing facilities, water treatment plants, process industries, material handling systems, HVAC installations, and industrial automation projects.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2146-4FB0 |
| SKU | 3RU2146-4FB0 |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | FB0 |
| Current Setting Range | 28–40 A |
| Relay Size | S3 |
| Trip Class | Class 10 |
| Operating Principle | Thermal |
| Mounting Type | 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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