Page 553 - Basic Electrical Engineering
P. 553
Figure 6.13 Exact equivalent circuit of a transformer
Figure 6.14 Approximate equivalent circuit of a transformer
Combining the resistances and reactances, the equivalent resistances R′ e
and equivalent reactance X′ are represented as Z′ as has been shown in Fig.
e
e
6.15.
This simplified equivalent circuit of the transformer can be used to
calculate the performance in terms of voltage regulation of the transformer
under various loading conditions.
6.9 PHASOR DIAGRAM OF A TRANSFORMER
The complete phasor diagram of a transformer at a lagging Pf load has been
shown in Fig. 6.16 (a).
Procedure for drawing the phasor diagram is given below.
Draw the flux vector as the reference vector along the x-axis. The voltage
induced in the two windings, E ans E will lag flux by 90°. If it is a step-up
1
2
transformer, E will be bigger in length than E . Otherwise, they can also be
2
1
