The Schneider Electric TeSys LRD3355A66 is a differential thermal overload relay for motor protection. It adjusts from 30 to 40 A and carries a Class 10A tripping curve per IEC 60947-4-1, meaning it protects standard induction motors against sustained overloads and phase-loss conditions. The relay trips at 1.14 ± 0.06 times the set current Ir per IEC 60947-4-1, and on phase failure it trips at 130 % of Ir on two phases with the third at zero. That differential action catches single-phasing before the motor cooks. Auxiliary contacts are 1 NO + 1 NC, rated 0.72 A at 500 V AC-15 for signalling circuits and 0.06 A at 440 V DC-13. The signalling circuit is fused at 4 A gG or 4 A BS.
The LRD3355A66 is certified to EN/IEC 60947-4-1 and 60947-5-1, UL 60947-4-1 and 60947-5-1, CSA C22.2 No 60947-4-1 and 60947-5-1, and GB/T 14048.4 and 14048.5. Rated insulation voltage is 1000 V per IEC 60947-4-1 for the power circuit, 600 V per UL and CSA. Impulse withstand is 6 kV per IEC 60947-1.
Power connections use M10 ring-lug terminals torqued to 11.3 N·m; control circuit uses screw clamp terminals accepting 1 to 2.5 mm² flexible or solid wire, torqued to 1.7 N·m. IP20 finger-safe protection for the enclosure.