This simulator holds a generic induction motor's rotor speed with an ideal dynamometer and lets you sweep it from below zero to well above synchronous speed, so you can directly compare motoring, the special zero-slip case, induction generating and plugging — all as different regions of the same slip equation.
• A real-time 3D view — laminated stator, three-phase windings, squirrel-cage rotor, stepped shaft, a synchronous-field reference ring, a rotor optical encoder and a field/rotor speed instrument — 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), a dynamometer-held rotor speed slider spanning −600 to 2200 rpm, and a rotor resistance multiplier, plus Start motor, Stop/coast and Reset trip 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 rotor speed, synchronous speed, slip, rotor electrical frequency, torque and real electrical input power. • An Experiments tab with four guided scenarios (typical motoring slip at 1450 rpm, "catching the field" at exactly 1500 rpm, driving the shaft at 1600 rpm to generate, and holding a negative mechanical speed to move against the field) 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.
Synchronous speed follows ns = 120f/poles and slip is s = (ns − n)/ns using a signed rotor speed, on 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). Rotor electrical frequency is fr = |s|f. Below synchronous speed with positive slip, the machine motors normally. At exactly synchronous speed (s = 0) the ideal cage sees no induction current and torque tends to zero, even though magnetizing current still flows — the field "catches" the rotor with nothing left to induce. Above synchronous speed, slip goes negative: an external prime mover must supply the mechanical energy to hold that speed, and the model's real electrical input power sign reverses — a negative reading denotes generation, not a free-energy result. Holding a negative mechanical speed (opposite rotation from the field) drives slip above 100%, the plugging regime, where the field actively opposes the rotor's motion.
Because an ideal dynamometer imposes speed directly in this model, you can explore every regime — including unstable ones a free-running motor would never settle into — just by moving the held-speed slider.
The torque/load/operating-point and speed/current history charts plot signed torque and slip across the full swept range, so the zero crossing at synchronous speed and the sign reversal above it are directly visible, alongside the corresponding real electrical input power sign flip when generating. Rotor electrical frequency fr = |s|f is shown as a separate metric because it stays positive in both the motoring and generating regimes even though slip itself changes sign.
Per the model's scope statement, the dynamometer here is idealized: it can supply or absorb mechanical energy without loss, so negative input power reflects the generating condition rather than a violation of energy balance. The underlying equivalent circuit is generic and fundamental-frequency only, excluding iron loss, saturation, supply unbalance, harmonics, detailed bearing dynamics and subcycle switching transients.
At s = 0 the ideal squirrel cage sees no relative fundamental flux change, so induction rotor current and torque tend to zero even though magnetizing current continues to flow. The "Catch the field" experiment holds rotor speed at exactly 1500 rpm (with 4 poles at 50 Hz) so you can see this directly.
Above synchronous speed, slip is negative and the machine operates as an induction generator: an external prime mover supplies mechanical energy through the dynamometer, and the model shows this as negative real electrical input power. It denotes generation, not a free-energy error.
Plugging is holding a mechanical speed opposite to the direction of the rotating field, which pushes slip above 100%. In that regime the field actively opposes the rotor motion, producing braking torque alongside large current and heating, as shown in the "Move against the field" experiment.
The dynamometer is idealized, able to supply or absorb mechanical energy without loss, so it can impose any held speed including unstable ones a free-running motor would never reach. The equivalent circuit itself is generic and excludes iron loss, saturation, supply unbalance, harmonics and subcycle switching transients.