This simulator models a generic electronic-trip, low-voltage, three-pole air circuit breaker — a 400 A frame example on a 400 V line-to-line, four-wire source/load reference with an unswitched neutral. Charge the closing spring, close onto a fixture, trip it and watch how the mechanism, protection electronics and arc chute clear the circuit.
• A real-time 3D cutaway of the three-pole breaker — copper conductors, silver contact tips, magenta arc zones, cyan sensors and violet trip electronics, with a toggleable enclosure, auto-rotate, expand and selectable components with callouts. • An operator station: charge spring, close breaker, open breaker, shunt trip test, reset trip latch, and a "hold close request" checkbox for trip-free testing. • Time controls: run time, advance 1 ms, advance 20 ms (one cycle), advance 1 s, and advance 60 s for a thermal study, with playback speed from 20x slow motion to real time to 10x fast-forward for overload study. • Source isolate/restore controls and a fixture selector: healthy load, balanced three-phase bolted short, or welded main contacts (all poles). • An Operating sequence readout and a per-pole status grid. • A Protection & oscillography tab with a current-interruption recorder (phase A amber, B turquoise, C purple), a logarithmic time-current characteristic chart, adjustable electronic L/S/I protection settings with enable/disable toggles for the short-time and instantaneous elements, the underlying electrical model equations, and a trip injection fixture that calculates expected cold decision time versus injected RMS current/Ir. • A Test & diagnose tab with a Verification bench (20 automated model checks), a diagnostic exercise (attempt to open, advance 20 ms, and identify why the opening failed), and a timestamped event log with session JSON export. • A Learn & assess tab with guided lessons, a knowledge-check quiz and a written model-scope statement with references.
The trip unit continuously compares sensed current against its long-time, short-time and instantaneous protection settings. Once the current-time curve is crossed, the electronics command the release mechanism to trip. In this model, contacts separate after an 8 ms release delay, then take 12 ms to complete their travel.
Separating the contacts alone doesn't clear the circuit — an arc forms across the widening gap and keeps conducting current. The arc only extinguishes at the next natural current zero after initial separation, which is why interruption timing depends on where in the AC cycle the contacts happen to part. The trip-free mechanism ensures the breaker can still complete this sequence and open even if an operator is holding the close command, which the simulator lets you verify directly.
The current interruption recorder plots actual modeled instantaneous current for the first 250 ms after a closing or opening command, with each phase extinguishing independently at its own current zero — that's why the three traces don't always stop at the same instant. The time-current characteristic chart uses logarithmic axes to show the trip unit's cold decision time as a function of current; real total clearing time also includes the mechanical release delay, contact travel and current-zero wait, which the injection fixture calculation folds in separately from the live circuit.
This is a teaching model, not a certified device curve: it excludes ground-fault and residual-current protection, DC interruption, arc-flash hazard energy, selectivity coordination and manufacturer trip tolerances. The I²t value shown is a numerical three-pole mean exposure integral, not a certified let-through rating, and above the modeled interrupting capacity the simulator does not claim a successful interruption.
The simulator models a generic electronic-trip low-voltage air breaker with adjustable long-time (L), short-time (S) and instantaneous (I) protection elements. Each element compares the sensed current against its pickup setting and, once the time-current characteristic curve is crossed, commands the trip unit to release the mechanism after a modeled 8 ms release delay and 12 ms of contact travel.
Trip-free means the breaker mechanism can still open on a protective trip even while someone is holding the close command. The simulator includes a "Hold close request (trip-free test)" checkbox so you can verify the breaker opens on a fault even with a sustained close signal.
The Test & diagnose tab includes a Verification bench that runs 20 automated checks against the underlying breaker model, plus a separate diagnostic exercise where you attempt to open the breaker, advance 20 ms, and identify why an opening failed (uncharged spring, welded contacts, or normal current-zero delay).
This is a teaching model of a generic 400 A frame breaker at 400 V line-to-line. It excludes ground-fault and residual-current protection, DC interruption, arc-flash energy, selectivity certification, and manufacturer trip tolerances. The plotted I²t is a numerical three-pole mean exposure integral, not a certified let-through rating, and above interrupting capacity the model does not claim successful interruption.