Schneider Thermal Overload Relay LRD3355

Schneider Electric LRD3355 Thermal Overload Relay

Reliable Motor Protection for Industrial Three-Phase Systems**

The Schneider Thermal Overload Relay LRD3355 is a dependable industrial protection device designed to safeguard medium-power three-phase motors and electrical circuits from prolonged overcurrent, phase loss, and unbalanced load conditions. Part of Schneider Electric’s trusted TeSys LRD range, this relay delivers accurate thermal protection, reducing motor damage risk and helping ensure smooth, uninterrupted operation in factory control panels, machinery systems, and commercial electrical installations across India.

🔌 What Is the Schneider LRD3355 Thermal Overload Relay?

The LRD3355 is a three-pole thermal overload relay with an adjustable current protection range of 30 – 40 A. It is engineered to monitor the current flowing through all three phases of a motor circuit and trip the motor supply when prolonged overcurrent or phase imbalance is detected, protecting the motor winding and related equipment from heat-related damage. It is commonly paired with Schneider Tesys contactors such as LC1D80 and LC1D95 to form robust motor starter assemblies.

This relay uses bimetallic thermal sensing elements to accurately sense current-induced heat and initiate a trip before damage occurs, offering effective protection while tolerating normal motor start-up currents.

🛠️ Key Features & Benefits

• Adjustable Current Range (30 – 40 A) – Customise overload protection to match the motor’s full-load current precisely, ensuring tailored safeguarding.

• Class 10A Trip Characteristic – Balances tolerance for inrush currents with quick response to sustained overloads, as per IEC standards.

• Three-Pole Thermal Monitoring – Continuously checks all phases to detect overload, phase loss, and unbalance.

• Phase Loss & Unbalance Detection – Trips promptly when irregular phase currents are detected, preventing motor stress and damage.

• Auxiliary Contacts (1NO + 1NC) – Signals overload faults to control panels or automation systems for enhanced monitoring and safety.

• Manual/Automatic Reset & Test Function – Offers flexible reset options and an easy test function to verify relay operation without powering down.

• Secure Screw-Clamp Terminals – Provides reliable, vibration-resistant wiring for both power and control circuits.

• Flexible Mounting Options – Can be installed beneath compatible contactors or on DIN-rail/panel for easy integration into control systems.

⚙️ Why Use the LRD3355 Overload Relay?

Thermal overload relays like the LRD3355 are essential in protecting motors from conditions that cause overheating, insulation breakdown, and premature failure. By detecting sustained overcurrent and abnormal phase conditions, this relay helps:

• Minimise unexpected downtime due to motor stress or failure

• Extend motor life by preventing heat-related damage

• Enhance system safety with early fault detection and signalling

• Reduce maintenance costs with reliable protection and reset/test features

• Seamlessly integrate with Schneider contactor-based motor starters for streamlined panels

📌 Typical Applications

The Schneider Thermal Overload Relay LRD3355 is ideal for use in:

• Motor starter assemblies in industrial control panels

• Pumps, compressors, and fan systems

• Conveyors & material handling equipment

• HVAC motor protection and ventilation systems

• Automated production line motor control

• Commercial and industrial power distribution panels

This makes it a reliable choice for electrical engineers, panel builders, and maintenance teams working on three-phase motor systems.