For the approximate equivalent circuit of Fig. 3.16(b), (suffix `eq’ is being dropped now),
lagging power factor (phase angle* 0 between V2 and 1) and in Fig. 3.17(b) for the leading power factor (pf). It is immediately observed from these phasor diagrams that for the phase angle indicated
It will be shown in Sec. 3.9 that V2 > V1 only when leading phase angle 0 is more than tan-l(R/X) (see Eq. (3.67).
In the plasor diagrams of Fig. 3.17(a) and (b) (these are not drawn to scale), the angle 6 is such that V1 leads V2. This is an indicator of the fact that real power flows from side 1 to side 2 of the transformer (this is proved in Section 8.9). This angle is quite small and is related to the value of the equivalent reactance: resistance of the transformer being negligible.