Schneider thermal overload relay LRN357N

The Schneider thermal overload relay LRN357N is an electrothermal relay specifically designed for motor overload protection, and it is suitable for industrial automation control systems.

 1. Core Parameters and Functions

 Current Range: The rated current range is 3750A, which can be accurately matched with motors whose rated current falls within this interval.

 Rated Voltage: It supports 690V AC and is applicable to most industrial threephase circuits.

 Trip Class: The trip class is 10, which means that in case of overload, the relay will trigger a protection action within 10 seconds and quickly cut off the circuit to prevent motor damage.

 Protection Functions:

   Overload Protection: Based on the principle of thermal expansion and bending of bimetallic strips, it monitors the motor current to avoid overheating caused by longterm overload.

   Phase Failure Protection: It detects the imbalance of threephase currents and prevents the motor from being burned out due to phasefailure operation.

   LockedRotor Protection: It trips quickly when the motor is locked during startup or operation.

 2. Installation and Connection

 Installation Methods:

   Combined Installation: It can be directly plugged into contactors of the LC1N50~N95 series to form a compact motor starter module.

   Independent Installation: It needs to be used with the LAEB1N base (order number) and fixed in the control cabinet with screws, which is suitable for occasions with limited space.

 Wiring Method: It adopts screwclamped terminals and usually supports a wire crosssectional area range of 2.56mm² to ensure a reliable connection.

 3. Reset and Operation

 Reset Methods:

   Manual Reset: After tripping, the reset button needs to be pressed manually to restore the circuit connection, so as to avoid safety risks caused by automatic restart.

   Automatic Reset: It can be switched to the automatic mode through a selector switch (use with caution to prevent false startup when the fault is not eliminated).

 Test Function: It is equipped with a test button, which can simulate overload tripping to verify the working status of the relay.

 4. Application Scenarios

 Motor Control: It is widely used for the protection of threephase asynchronous motors such as fans, water pumps, and compressors, and is especially suitable for equipment with frequent startup/shutdown or large load fluctuations.

 Industrial Control Cabinets: As a core component of motor starters, it ensures the longterm stable operation of the system.

 Compatibility: It is perfectly matched with contactors of the Schneider LC1N series, simplifying the selection and installation process.

 5. Price and Procurement

 Reference Price: Depending on the procurement channel and quantity, the unit price ranges from 100 to 200 RMB. For bulk procurement, you can contact via WhatsApp: 0086138112554325 for negotiation.

 Genuine Verification: Purchase through official Schneider channels or authorized distributors to ensure the product has anticounterfeiting marks and complete packaging, and avoid counterfeit products.

 6. Precautions

 Environmental Conditions: The normal operating temperature range is usually 25℃~+60℃, and exposure to hightemperature, humid, or corrosive environments should be avoided.

 Rated Current Setting: Before installation, adjust the dial according to the rated current on the motor nameplate to ensure that the protection sensitivity matches the actual load.

 Maintenance Recommendations: Regularly check the tightness of terminals and the condition of bimetallic strips, and clean dust to maintain stable performance.

 7. Comparative Selection

 Comparison with LRN355N:

   Current Range: LRN355N has a range of 3040A and is suitable for lowpower motors; LRN357N covers 3750A and is suitable for medium and highpower equipment.

   Contactor Matching: LRN355N is compatible with LC1N40~N95 contactors, while LRN357N is compatible with LC1N50~N95 contactors. The selection should be based on the contactor model.

 8. Certifications and Standards

 International Certifications: It complies with the standards of IEC 6094741 (Lowvoltage switchgear and controlgear) and UL 508 (Industrial control equipment), ensuring global universality and safety.

 Summary

With its reliable protection performance, flexible installation methods, and wide compatibility, the Schneider LRN357N thermal overload relay has become an ideal choice for industrial motor control. During selection and use, comprehensive consideration should be given to motor parameters, installation space, and system requirements to ensure the safe and efficient operation of the equipment.