A three-phase synchronous motor with a wound field on the rotor. The rotor is fed with direct current through slip rings and becomes an electromagnet that "locks" onto the rotating stator field and turns at exactly the synchronous speed — set only by the supply frequency and the number of pole pairs, never by the load. It cannot start from standstill on its own, so a starting (damper) winding acting as a cage runs it up; once in step it runs precisely synchronously. The field current controls the reactive power and power factor (an over-excited motor feeds reactive power back into the grid). Overloaded beyond its pull-out torque, the motor falls out of step. The model shows the torque M, the field current and whether it is in synchronism.
This page is a utility for simulating wound-field synchronous motor (3-phase) online with specified initial values.
Using the model. The three stator switches start the motor — the damper winding runs it up and then it pulls into step (running in synchronism). A separate source and a field rheostat set the rotor current: move its slider and watch the stator current and power factor change while the speed stays constant. The speed changes only with the "supply frequency" slider — the hallmark of a synchronous machine. The "load torque" slider sets the load; overload it and the motor falls out of step. Scopes: stator current I(stator), field current I(field) and voltage U(L1‑L2).
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