Details

The left diagram shows a rotating field (brown vector) that is the vector sum of three alternating fields (black vectors). The rotating field is circular if:

1. the spatial directions of the alternating fields differ by 120 degrees

2. the phases of the alternating fields differ by 120 degrees

3. the alternating fields have equal amplitudes

If one of the alternating fields has an amplitude error or a phase error, the resulting rotating field is elliptical. (Try the sliders "amplitude error" and "phase error" to check this.)

The right diagram shows the vector sum of the clockwise-rotating (green vectors) and counterclockwise-rotating (blue vectors) components of the three alternating fields.