This simulator models a generic forward/reverse induction motor starter — two mutually interlocked contactors that swap two supply phases to reverse the rotating field. Observe the interlock, compare a controlled coast-then-reverse sequence with an explicitly enabled high-slip plugging experiment, and watch how the rotor's stored kinetic energy shapes every transition.
• A real-time 3D cutaway — finned motor frame, laminated stator, three-phase windings, squirrel-cage rotor, stepped shaft, bearings, cooling fan, fan shroud/endshields, six-terminal connection box, main contactor K1, reverse contactor K2, a mechanical/electrical interlock, a supply isolator and a forward/reverse phase-order trainer — with home view, focus-selected-part, full-enclosure toggle, exploded view, auto-rotate, expand and selectable labeled components. • Motor & controller settings: line-to-line supply voltage (200–460 V RMS), supply frequency (40–60 Hz), pole count (2/4/6), load torque at base speed, load law (constant or fan/pump demand), combined inertia, and an "enable at-speed plugging experiment" checkbox, plus Start motor, Stop/coast, Reset trip, Coast then reverse and Swap phase sequence actions. • A Curves & measurements tab with a torque/load/operating-point chart, a speed-and-current history chart, the full model equations, and live snapshot readouts of signed rotor speed, signed-field slip, line current, signed torque, current-squared integral and rotor copper loss. • An Experiments tab with four guided scenarios (a normal forward run, selecting reverse at rest before starting, coasting before reversing, and an explicit plugging investigation with phase swap at speed) plus a Run model checks verification bench and a timestamped event log with trial-report export. • A Learn & assess tab with four guided lessons, a two-question knowledge-check quiz and a written model-scope statement with an external reference link.
Swapping two of the three supply phases reverses the direction of the rotating stator field, which the model represents as a sign flip on synchronous speed. The rotor's speed cannot change instantaneously because it stores kinetic energy — J dω/dt = Te − Tload − 0.012ω governs the transition, using the same generic equivalent circuit as the other motor labs (Rs = 0.65 Ω, R2′ = 0.45 Ω, Xs = X2′ = 1.1 Ω, Xm = 28 Ω at 50 Hz). K1 and K2 are mutually exclusive with a modeled 80 ms open interval between them, and a coast reversal explicitly waits until rotor speed drops below 8 rad/s before allowing the opposite contactor to close.
Plugging — reversing the field while the rotor is still moving forward — must be explicitly enabled with the "enable at-speed plugging experiment" checkbox. In that mode, slip exceeds 100% and the opposing field first brakes the still-forward-moving rotor before it can accelerate in reverse, which produces large current and heating that the current-squared integral tracks.
Because direction matters here, the metrics and charts use signed rotor speed, signed-field slip and signed torque rather than magnitudes — a negative value simply means the opposite rotational direction from the currently selected "forward" phase sequence. Comparing the coast-then-reverse experiment against the plugging experiment on the same charts makes the current and I²t difference between the two strategies directly visible.
Per the model's scope statement, the numerical model permits high-slip plugging for teaching purposes but does not certify contactor making-duty ratings or motor thermal withstand for real plugging applications. The underlying equivalent circuit also excludes iron loss, saturation, supply unbalance, harmonics, detailed bearing dynamics and subcycle switching transients, and the interlock timing (80 ms open interval, 8 rad/s coast threshold) is a teaching approximation, not a manufacturer specification.
Swapping two supply phases reverses the rotating field immediately, but the rotor itself stores kinetic energy and its speed can only change according to the torque margin acting on the combined inertia. The simulator shows torque changing sign before speed does, since the mechanical equation integrates that margin over time.
Coast then reverse opens the active contactor and waits for rotor speed to drop below a low threshold (8 rad/s) before closing the opposite contactor, avoiding a high-slip condition. Plugging — available only when explicitly enabled — reverses the field while the rotor is still moving, applying an opposing field that brakes it directly but can produce large current and heating.
K1 (forward) and K2 (reverse) must never close at the same time, because that would connect crossed supply phases directly across each other. The simulator models a mechanical/electrical interlock plus an 80 ms open interval between the two contactors to prevent simultaneous closure.
The plugging experiment is a numerical teaching approximation — it does not certify real contactor making-duty ratings or motor thermal withstand for plugging duty. The underlying motor equivalent circuit is generic and excludes iron loss, saturation, supply unbalance, harmonics and subcycle switching transients.