The C166TM125C is a thermal-magnetic trip unit from the Schneider Electric ComPacT NSX100...250 range, designed for fixed-mount circuit breakers in distribution applications. It carries a 125 A rating at 50 °C and complies with EN/IEC 60947-2, the standard that governs low-voltage switchgear and controlgear — so it meets the breaking, coordination, and insulation requirements for industrial panel builds. The TM-D unit provides LI protection: a thermal (L) element for overloads and a magnetic (I) element for short-circuits. The long-time pick-up Ir is adjustable from 0.7 to 1 x In, and the instantaneous pick-up Ii is fixed at 1250 A — meaning it will trip magnetically at ten times the rated current, which gives good selectivity with downstream breakers on a motor or distribution feeder.
Deployment context
This trip unit snaps into a ComPacT NSX100...250 circuit breaker frame. The 4-pole 3D configuration protects three phases with no neutral protection.