The LRD21TQ is a differential thermal overload relay from the TeSys Deca series, designed for motor protection in three-phase circuits. Its 12...18 A adjustment range and Class 10A trip curve mean it protects motors with a full-load current in that band against sustained overloads, tripping within 10 seconds at 7.2× Ir — a standard match for standard induction motors driving pumps, fans, or conveyors. The differential action also detects phase-loss conditions: it trips at 130% of Ir on two phases with the third at zero, which is the IEC 60947-4-1 requirement for phase-failure sensitivity.
Mounts directly under the contactor or on a plate/rail with specific accessories. The screw-clamp terminals accept up to 10 mm² flexible on the power circuit and 2.5 mm² on the control circuit. Tightening torque is 2.5 N·m for power and 1.7 N·m for control. The 1 NO + 1 NC auxiliary contact composition is the standard feedback pair for a PLC input and a holding circuit.