The Schneider LRD3321A66 is a TeSys Deca differential thermal overload relay for motor protection, with a thermal protection adjustment range of 12-18 A and a Class 10A tripping curve per IEC 60947-4-1. It protects three-phase motors against overload, phase failure, and phase unbalance — the phase failure sensitivity trips at 130% of Ir on two phases with the third at zero current. Rated insulation voltage (Ui) is 1000 V per IEC for the power circuit, and the impulse withstand voltage (Uimp) is 6 kV per IEC 60947-1.
The 12-18 A adjustment range matches a motor full-load current in that band. Class 10A allows the relay to ride through normal starting inrush without nuisance tripping. The signalling circuit is rated 1.5 A at 240 V AC-15 and 0.1 A at 250 V DC-13 — these are the contact ratings for the 1 NO + 1 NC auxiliary contacts, so the relay can directly switch a PLC input or contactor coil within those limits. IP20 finger-safe protection means it is suitable for enclosure mounting where no washdown or dust ingress is expected — standard for a panel-mounted overload relay.
The LRD3321A66 carries approvals to EN/IEC 60947-4-1, EN/IEC 60947-5-1, UL 60947-4-1, UL 60947-5-1, CSA C22.2 No 60947-4-1, CSA C22.2 No 60947-5-1, and GB/T 14048.4/5 — covering global motor protection and control circuit standards. Flame retardance is V1 per UL 94, and climatic withstand conforms to IACS for marine or humid environments.