A three-phase squirrel-cage induction motor — the workhorse of industry. The three-phase stator winding produces a rotating magnetic field that induces currents in the rotor bars; their interaction with the field creates torque. The rotor always turns slightly slower than the field — this lag is the slip s, and it is what produces the torque (at s = 0 the torque is zero). The motor is simple, rugged and self-starting, but at start-up it draws 5–7 times the rated current. The model shows the torque M, the speed n (rpm), the slip s and the direction of rotation.
This page is a utility for simulating squirrel-cage induction motor (3-phase) online with specified initial values.
Using the model. Close the three switches to energise the stator — the scopes show the inrush current (several times the running value) and the run-up. Use the "supply frequency" slider to set the speed (variable-frequency control, as in a VFD): the frequency directly sets the synchronous speed of the field. The "supply voltage" slider acts as a soft-starter that limits the inrush. The "load torque" slider changes the shaft load — watch the slip grow with it. The scopes at the bottom show the line voltage U(L1‑L2) and the phase current I(L1). Swap any two phases and the motor reverses.
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