The Siemens 3MU7110-0JA0 Thermal Overload Relay is a reliable motor protection device from the SINOVA 3MU7 Series, designed to safeguard three-phase motors against overload and phase-failure conditions. Featuring a 2.5A to 4A adjustable current range and a Class 10 tripping characteristic, this thermal overload relay provides dependable protection for industrial motor control systems, helping prevent overheating, insulation damage, and costly motor failures. It is specifically designed for direct mounting on Siemens 3MT7 contactors (Size 0, 1, and 2), creating a compact and efficient motor starter assembly.
The relay continuously monitors motor current using a thermal bimetal mechanism that closely follows the heating characteristics of the motor. When an overload condition occurs, the relay trips and disconnects the motor before excessive heat can cause damage to windings or insulation. This inverse-time operating principle ensures reliable protection while minimizing nuisance tripping during normal operation.
With its Class 10 trip characteristic, the 3MU7110-0JA0 is ideal for motors operating under normal starting conditions. The relay responds rapidly to overload situations while allowing standard startup currents to pass without unnecessary interruption. Typical applications include pumps, fans, compressors, conveyors, packaging machinery, HVAC systems, and industrial automation equipment.
The adjustable 2.5A to 4A current range allows precise matching of protection settings to motor full-load current requirements. The relay has a rated operational current of 4A, supporting motors up to approximately 1.5 kW at 400V and 3 kW at 690V, making it suitable for small and medium-duty motor applications.
A key safety feature of the Siemens 3MU7110-0JA0 Thermal Overload Relay is its integrated phase-failure sensitivity. In the event of a phase loss, the relay accelerates tripping to minimize motor heating and prevent winding damage. This enhanced protection significantly improves motor reliability and operational safety in industrial environments.
Designed for seamless integration with Siemens 3MT7 contactors, the relay features robust screw terminal connections for both the main and auxiliary circuits. These terminals ensure secure wiring, easy installation, and reliable long-term performance in demanding industrial applications.
The relay includes 1 Normally Open (NO) auxiliary contact for overload trip indication and 1 Normally Closed (NC) auxiliary contact for contactor disconnection. These contacts support alarm signaling, PLC interfacing, motor protection circuits, and remote monitoring applications.
For operational flexibility, the 3MU7110-0JA0 supports both manual and automatic reset functions, allowing users to select the most appropriate reset method based on safety requirements and application needs. A built-in trip indicator further simplifies fault diagnosis and maintenance.
Built according to IEC 60947-4-1 standards, the relay offers 690V insulation voltage, 6kV impulse withstand voltage, IP20 front protection, and reliable operation in ambient temperatures from -5°C to +55°C. Its rugged construction makes it ideal for manufacturing plants, water treatment facilities, HVAC installations, process industries, and industrial automation projects.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Brand | Siemens |
| Series | SINOVA 3MU7 |
| Model Number | 3MU7110-0JA0 |
| SKU | 3MU7110-0JA0 |
| Product Type | Thermal Overload Relay |
| Current Setting Range | 2.5A – 4A |
| Rated Operational Current (Ie) | 4A |
| Trip Class | Class 10 |
| Relay Size | Size 1 |
| Mounting Type | Direct Contactor Mounting |
| Compatible Contactors | Siemens 3MT7 Size 0, 1 & 2 |
| Main Circuit Connection | Screw Terminals |
| Auxiliary Circuit Connection | Screw Terminals |
| Auxiliary Contacts | 1NO + 1NC |
| Protection Functions | Overload Protection, Phase Failure Protection |
| Reset Function | Manual / Automatic Reset |
| Number of Poles | 3 Pole |
| Rated Operational Voltage | Up to 690V AC |
| Motor Rating @ 400V | 1.5 kW |
| Motor Rating @ 690V | 3 kW |
| Operating Frequency | 50/60 Hz |
| Rated Insulation Voltage (Ui) | 690V |
| Rated Impulse Withstand Voltage (Uimp) | 6kV |
| Protection Rating | IP20 |
| Operating Temperature | -5°C to +55°C |
| Storage Temperature | -25°C to +70°C |
| Relative Humidity | 10% – 95% |
| Height | 64 mm |
| Width | 44 mm |
| Depth | 92 mm |
| Weight | Approx. 0.15 kg |
| Standards Compliance | IEC 60947-4-1 |
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