This simulator models the sequenced availability of a standby generator backing up a UPS-fed data center load after a utility failure — detection delay, engine cranking, voltage/frequency stabilization and transfer-switch selection — while an online UPS bridges the gap on battery. Adjust load, battery size and timing, fail the source, and watch how much stored energy is used before the generator becomes available.
• Facility laboratory tab: a real-time 3D scene of the engine-driven standby generator (engine block, alternator, radiator, belt fan, exhaust silencer, day tank), the generator transfer switch, utility sensing terminals, the engine starting battery, a sequence controller showing start delay/cranking/stabilization/available states, and the UPS-backed essential load — with camera controls and a clickable component list; live metrics (IT load served, unserved load, battery state of charge, battery DC output, conversion loss, net battery energy out); controls for IT load, utility available and generator available checkboxes, battery energy (kWh), initial battery SOC on a new trial, failure detection/start delay, cranking duration and voltage/frequency stabilization time; and action buttons to enable the facility, stop the experiment, lose utility and restore utility. • Curves & measurements tab: the governing equations (available time = detection delay + crank time + stabilization time; battery energy during the gap ≈ IT power × available time / (3600 × efficiency)) alongside live and historical readouts. • Experiments tab: guided scenarios — a normal standby sequence (lose utility and watch delay/crank/warm-up progress before the generator becomes available), slow stabilization (25 s warm-up, more battery energy consumed), a failed start (disable generator availability so the UPS carries the load on battery until depletion or utility returns), and no battery headroom (start at 5% reserve so load goes unserved during startup) — plus a model verification bench (independent fresh-model checks) and an event log. • Learn & assess tab: lessons on detecting source failure, cranking and stabilizing before transfer, transferring only to an available and qualified source, and what happens on a failed start, plus a knowledge-check quiz with reset and a scope/references note.
When utility power is lost, the model does not assume the generator is instantly available. A configurable detection/start delay separates the moment utility is lost from the moment a start command is issued. The engine then cranks for a set duration, and even once running, the alternator's voltage and frequency must stabilize before the output is considered qualified. Only after all three stages complete does the transfer switch treat the generator as an available source and transfer the load to it — this is an open-transition switch that never parallels unmatched sources.
During the entire gap between utility loss and generator availability, the UPS's battery carries the essential load, drawing down state of charge. If the generator fails to start (availability disabled), the battery must support the load indefinitely until utility returns or the battery's reserve is depleted, at which point load goes unserved.
The available-time equation (detection delay + crank + stabilization) directly drives how long the UPS battery must bridge the gap, and the energy equation shows that energy drawn is proportional to both the IT load and that total ride-through time, divided by round-trip efficiency — so slower stabilization or longer cranking measurably increases the net battery energy consumed, which you can see directly in the net-battery-energy-out metric after running the slow-stabilization experiment.
The model verification bench builds independent, fresh model instances to check invariants in the sequencing and energy-balance logic — separate from your live trial — while the fixture itself assumes a 96% mains-conversion and 94% battery-conversion efficiency online double-conversion UPS with a 5% reserve floor and 95% charge ceiling. This is a sequenced-availability and averaged energy-balance model, not an engine, governor or AVR solver — it does not simulate AC waveforms, short-circuit current, source synchronization, a manufacturer's protection curve, or an automatic static-bypass algorithm.
The model separates detecting the failure from starting the engine, cranking the engine, and stabilizing voltage and frequency. All three stages must complete — a configurable delay, cranking duration, and warm-up/stabilization time — before the transfer switch treats the generator as an available, qualified source.
The existing UPS battery model bridges the gap, discharging from its initial state of charge to supply IT load throughout detection, cranking and stabilization, until the transfer switch selects the now-qualified generator.
With generator availability disabled, the sequence shows FAILED TO START and the battery continues supporting the load. If the battery is depleted before utility returns, IT load goes unserved.
The model verification bench builds independent, fresh model instances (not touching your live trial) and checks invariants in the sequenced-availability and energy-balance logic, confirming the teaching model behaves consistently.