Overview
The Siemens 3UA5900-2M is a thermal overload relay engineered for reliable motor protection in industrial control applications. Part of the proven 3UA series, this relay delivers dependable overload and phase-failure protection across AC and DC motor circuits from fractional to 400A capacity. Built for DIN rail mounting on contactor assemblies, it combines simplicity with proven performance in harsh industrial environments.
Key Features
- Thermal bimetallic protection mechanism with temperature compensation
- Setting range: 32–45A with 160A fuse link rating
- Manual and automatic reset selectable options
- Auxiliary contact 1NO–1NC for signaling and control circuits
- ON/OFF indication for operational status monitoring
- Screw terminal connections for secure wiring
Technical Specifications
| Setting Range | 32–45 A |
| Fuse Link Rating | 160 A |
| Trip Class | Class 10A (IEC 60947-4-1) |
| Number of Poles | 3 |
| Auxiliary Contacts | 1NO–1NC |
| Reset Type | Manual / Automatic selectable |
| Terminal Type | Screw terminals, M5 |
| Mounting Style | DIN rail / Contactor-mounted |
| Ambient Temperature | Temperature compensated |
| Certifications | IEC 60947-4-1, CE marked |
| Protection Type | Thermal bimetallic |
| Switching Capacity (380V AC) | AC-15 |
| Weight | ~0.28 kg |
Typical Applications
- Motor Protection: Overload and single-phase failure protection for three-phase AC motors in pump, fan, and conveyor drives
- Industrial Control: Integration with 3TF contactors and motor starter assemblies
- Machine Tools: Spindle motor and auxiliary drive protection
- HVAC Systems: Compressor and fan motor safeguarding
- Renewable Energy: Motor protection in wind turbine yaw and pitch control systems
Compatibility & Replacements
The 3UA5900-2M is part of Siemens’ legacy 3UA series and is designed for mounting on compatible 3TF contactors and motor starters. While the 3UA series remains available in OEM service applications, engineers should verify contactor model compatibility and consider modern alternatives such as the 3RB and SIRIUS 3RB2 series for new installations. For drop-in replacement in existing assemblies, consult Siemens technical documentation or contact your local distributor to confirm auxiliary contact and terminal screw dimensions. This relay carries standard IEC 60947-4-1 certification and CE marking for European industrial use.
