This simulator models a generic delayed open-transition, three-pole automatic transfer switch (ATS) cabinet backed by a diesel/gas generator on a 480 V reference system. Fail the normal source, watch the controller start and qualify the generator, transfer the load through a deliberate both-open interval, and study controlled retransfer and cooldown.
• A real-time 3D cutaway workbench of the ATS cabinet — normal-source and generator-source three-pole contacts with a mechanical interlock, the engine/alternator package, the source monitor and sequencer, and the essential-load distribution panel — with toggleable enclosure, exploded view, auto-rotate, expand and selectable numbered components with callouts. • Experiment controls: pause/resume, advance 0.1 s, advance 1 s, and a playback selector from 10x slow motion to real time to 1 minute per second. • Eleven fixture controls: normal-source voltage (% nominal), generator fail-to-start, loss confirmation/start delay, generator acceleration time, generator qualification time, both-open transition dwell, stable-utility retransfer delay, unloaded cooldown, requested load (kW), generator capacity envelope (kW), and an automatic-return-to-normal toggle. • Direct actions to start/stop a trial, fail the utility source and restore the utility source. • An operating-sequence readout, a per-source contact-state token display and a live readings table. • A Curves & measurements tab with two charts (normal-source vs. generator voltage; normal vs. generator contact state), the underlying model equations, and snapshot readouts. • A Test & diagnose style Experiments tab with four guided experiments (utility failure, generator-fails-to-start, undersized backup generator, non-return mode) plus a Verification bench of automated model checks and a timestamped event log with a trial-report export. • A Learn & assess tab with four guided lessons, a two-question knowledge-check quiz and a written model-scope statement with a manufacturer reference link.
The source monitor treats the normal source as acceptable between 90% and 110% of the 480 V nominal reference; anything outside that band, once confirmed for the selected loss-confirmation delay, sends a generator-start request. The four-pole 60 Hz alternator ramps toward 1800 rpm over the selected acceleration time, and voltage scales with speed for the startup visualization (AVR dynamics are not solved). Once the generator reaches rated speed it must remain stable through a separate qualification interval before the sequencer will use it.
Transfer itself is break-before-make: the normal contacts open, the both-open transition dwell elapses, the target source is re-checked, and only then do the generator contacts close — the interlock logic keeps normal-contact + generator-contact ≤ 1 at all times, so the two sources can never be closed together. Served power on generator is capped at min(requested demand, generator capacity), exposing unserved demand when the capacity envelope is undersized. When the normal source is stable again, retransfer follows the same open-dwell-close pattern (unless automatic return is disabled), after which the generator runs its unloaded cooldown interval before stopping.
The voltage chart compares the normal-source and generator voltage traces, and the contact-state chart shows exactly when each source's three-pole contacts are closed — useful for confirming the both-open dwell and that sources never overlap. The event log timestamps every contact and sequencer state change and can be exported as a trial report.
Per the model's own scope statement: this is a representative delayed open-transition ATS, not a manufacturer study. Neutral switching, synchronization for closed-transition operation, transient motor residual voltage, AVR/governor dynamics, real generator overload protection and code-required transfer times are not modeled. Source thresholds and timer values are educational settings, not device recommendations, and engine rotation plus current markers are deliberately slowed illustrations rather than real-time physical motion.
The simulator treats the 480 V normal source as acceptable between 90% and 110% of nominal. Once voltage is out of that range continuously for the selected loss-confirmation/start delay, the controller issues a generator-start request — brief dips shorter than the delay do not trigger a transfer.
No. The model enforces normal-contact + generator-contact ≤ 1 at all times, representing the mechanical and logical interlock of a break-before-make, open-transition switch. There is always a both-open transition dwell between opening one source and closing the other.
Served power on the generator is capped at the minimum of requested demand and the configured generator capacity envelope. Set "Requested load" above "Generator capacity envelope" to see unserved demand appear even after a successful transfer.
It excludes neutral switching, closed-transition synchronization, transient motor residual voltage, alternator AVR/governor dynamics, a full generator overload-protection scheme, and code-mandated transfer time requirements. Timer and threshold values are educational defaults, not equipment specifications.