Phase sequence: It is the order in which the three phases reach their peak or maximum values. It is shown in below fig. the phase sequence is A-B-C (or R-Y-B). In the following waveforms, it is seen that the R phase voltage attains the positive maximum value first, and after angular distance of 120º, Y-phase voltage attains its positive maximum and further after 120º, B- phase voltage attains its positive maximum value. So the phase sequence is R-Y-B.