Rotating magnetic field

Take three sinusoidal voltages of the same amplitude and frequency and dephase them by 120 degrees to create a balanced three-phase system. Such systems, easily generated by an alternator, distribute power in such a way that there is little loss along power lines.

Three phase systems, used all over the world, have other advantages. Running these dephased currents through coils geometrically shifted 120 degrees from each other creates a magnetic field. Remarkably, this magnetic field is "rotating". Thus a rotating magnetic field can be created from a fixed armature winding.

This opens the door to "electric" rotating machines.

• To observe a well-known application of the principle of superposition.
• To illustrate how to use fixed armature windings as electromagnets.
• To illustrate how three-phase voltages can be used to generate a rotating magnetic field from fixed armature windings.

Click on the "vector addition" button to see the superposition of the three individual magnetic field vectors.