Trip unit for ComPacT NSX250 — MicroLogic 5.2 A-Z, 250 A
The C2535Z250 is a MicroLogic 5.2 A-Z electronic trip unit, part of the Schneider Electric ComPacT NSX100...250 range. It is rated 250 A at 40 °C, 3 poles protected (3D), and provides LSI protection — long-time (L), short-time (S), and instantaneous (I) — for special applications on 16 Hz 2/3 networks. The trip unit carries an LCD display for local metering and communicates energy data, protection settings, time-stamped events, and demand values.
What the LSI protection settings mean for coordination
The long-time pickup (Ir) is adjustable from 100 to 250 A in nine steps, with a delay range of 15–400 s at 1.5 × Ir down to 0.5–16 s at 6 × Ir — this governs overload protection for cables and transformers. Short-time pickup (Isd) adjusts from 1.5 to 10 × Ir with a delay of 0–0.4 s (I²t on or off), giving selectivity against downstream faults. Instantaneous pickup (Ii) spans 1.5 to 12 × In, clearing hard bolted faults within one cycle. Zone selective interlocking (ZSI) is included, which ties upstream and downstream trip units together to reduce arc-flash energy while preserving coordination — critical for panel designers who need both speed and discrimination.
Integration into a ComPacT NSX250 panel
The trip unit mounts into a fixed-mount ComPacT NSX250 circuit breaker, 3-pole, with protected poles designated 3D. It carries an IP40 rating per IEC 60529, meaning it is protected against tools and small wires larger than 1 mm — suitable for enclosed panel installation. The LCD display and local signalling (green ready LED, red overload LED at 105 % Ir and orange at 90 % Ir) give the commissioning engineer immediate status without a connected controller.