This simulator models a representative 400 V star-connected, 50 Hz, 4-pole three-phase squirrel-cage induction motor with roughly 3 kW of mechanical load. Energize it, apply a mechanical load law or fault, and watch how slip, induced rotor current and torque relate to each other as the rotor tries — and fails — to catch the rotating stator field.
• 01 Motor workbench: a real-time 3D cutaway model with a motor view, end view, toggleable cutaway, auto-orbit camera and expand view, clickable components with callouts, and colored rotor bars showing induced-current polarity, with rotation slowed 40× while preserving field/rotor speed ratios. • Energize/open-contactor controls, run-time/step (0.1 s)/advance 1 s/advance 60 s time controls, reset lab and reset-protection buttons, a mechanical-load-law selector (constant resisting torque, or fan/pump torque ∝ speed²), a fault-fixture selector (30% voltage sag, 3× mechanical load, locked shaft, 2× stator resistance, 2× referred rotor resistance, cooling impaired), and a modeled current/temperature protection toggle. • A field/rotor/slip waveform chart of reconstructed instantaneous winding currents, plus a motion readout, and supply/drive/protection controls with an operating-note callout. • 02 Circuit & power: a per-phase equivalent circuit diagram (R₁, jX₁, core-loss/magnetizing branch Rc/jXm, referred rotor branch R₂′/s and jX₂′) with live circuit values, the governing formulas (ns = 120f/poles, slip, air-gap power, torque, converted power), a calculated power-flow breakdown with an energy-check callout, and equivalent-circuit parameter controls. • 03 Curves & diagnostics: a torque-vs-speed chart (electromagnetic torque, load + friction torque, live operating point), an operating-history trend chart (rotor/sync speed, torque, current, temperature or slip over the most recent ~60 seconds), a dynamometer mode (free acceleration vs. external-dynamometer held-speed with an adjustable held RPM from -2,500 to 3,000), a data-export button and a diagnostic event log. • 04 Experiments & tests: a 22-check verification bench and isolated experiment fixtures. • 05 Learn & quiz: guided lessons, a model-scope statement with a reference, and a knowledge-check quiz, plus a "Start guided tour" button.
The stator windings create a rotating magnetic field at synchronous speed ns = 120f/poles. The rotor can never spin exactly at that speed under load, because it's the relative motion between the field and the rotor bars — the slip — that induces the rotor currents in the first place. Slip s = (ns − nr)/ns, and the frequency of the induced rotor currents is simply |s| times the supply frequency.
Air-gap power Pag = 3|I₂′|²R₂′/s splits into rotor copper loss and mechanical power converted at the shaft: Pconverted = (1 − s)Pag. Electromagnetic torque is Pag divided by synchronous angular velocity. This is why locking the shaft (the "jam" fault fixture drives slip to 1) produces high rotor current and heating without any useful mechanical output, and why the fan/pump load law reaches a different steady-state slip than a constant-torque load of the same nominal magnitude.
The per-phase equivalent circuit puts stator resistance R₁ and leakage reactance jX₁ in series with a parallel combination of the core-loss/magnetizing branch (Rc, jXm) and the referred rotor branch (R₂′/s, jX₂′). Because R₂′/s depends on slip, this one circuit describes the motor's behavior all the way from standstill (s = 1) through normal running slip to above-synchronous generating operation (negative slip) — which you can force directly using the dynamometer's held-speed mode.
The torque-speed chart plots electromagnetic torque against the load-plus-friction torque curve, and their intersection is the stable operating point shown in the live trend. The increased-rotor-resistance fault fixture is explicitly not a broken-bar diagnostic model — it's a uniform R₂′ change, useful for exploring how rotor resistance shifts the torque-speed curve's breakdown point rather than for simulating a real fault signature. This is a balanced sinusoidal steady-state model recalculated as speed and temperature evolve; saturation, skin effect, PWM harmonics, negative-sequence imbalance and detailed rotor-bar currents are outside its scope.
Slip is the fractional difference between the stator's synchronous field speed (ns = 120f/poles) and the actual rotor speed. The rotor bars only have current induced in them because they are moving relative to the rotating field, so under any real load the rotor must run slightly slower than synchronous speed to sustain that induced current and produce torque — running exactly at synchronous speed would mean zero relative motion and zero induced torque.
Locking the shaft forces slip to 1, the maximum possible value. This produces high induced rotor current and correspondingly high rotor copper loss and heating, since air-gap power (Pag = 3|I₂′|²R₂′/s) is all being dissipated as loss rather than converted into mechanical output (Pconverted = (1 − s)Pag = 0 when s = 1).
In held-speed (clamp) mode, an external dynamometer forces the shaft to a chosen speed from -2,500 to 3,000 rpm regardless of the configured load, overriding free acceleration. This lets you study operation above synchronous speed (generating) or with field and rotor rotating in opposite directions (plugging) — operating regions that a normally loaded, freely accelerating motor would not reach on its own.
This is a balanced, sinusoidal steady-state per-phase model recalculated as speed and temperature evolve, with dynamic mechanical acceleration and a lumped thermal model. It does not solve saturation, skin effect, switching/PWM harmonics, negative-sequence phase imbalance, bearing wear spectra or detailed rotor-bar current distributions, and the increased-rotor-resistance fixture is not a broken-bar diagnostic model.