We know that when the coil rotates in a magnetic field, the wire cuts the magnetic field lines to produce an induced electromotive force, and its variation can be expressed by a sinusoid. If we take three coils and they are at a spatial difference of 120 degrees, the three coils still rotate at the same speed in the magnetic field, and will induce three induced electromotive forces of the same frequency. Since the three coils are at an angle of 120 degrees from the spatial position, the generated current is also a three-phase sinusoidal change called a three-phase sinusoidal alternating current. Industrial electricity uses three-phase electricity, such as three-phase AC motors.
The voltage between any two phases is 380V, and any relative ground voltage is 220V. Divided into a phase, phase B, phase C. The line is represented by L1, L2, and L3. (Three-phase AC power has 660V and 6000V power supply depending on the application).