Electrical Engineering ⇒ Topic : Phasor Diagrams Using R.M.S. Values

Phasor Diagrams Using R.M.S. Values

The r.m.s. values of voltage and current are much more important than maximum values because a.c. ammeters and voltmeters are calibrated to read the r.m.s. values. Consequently, it is much more convenient to draw the phasor diagram using rm. s. values rather than maximum values. This does not *alter the phase difference (Φ) between the phasors because only the lengths of the phasors are changed. However, such a phasor diagram (using rm. s. values) will not generate the sine wave of proper amplitude unless the lengths of the phasors are first multiplied by √2. Remember, for a sine wave, maximum value is equal to √2  times the rm. s. value. Fig.a (i) shows the phasor diagram using maximum values while Fig. a (ii) shows the same phasor diagram in terms of r.m.s. equivalent.

                                                                                       figure (a)

In all the phasor diagrams from now onwards, we shall use the r.m.s. values.