PPT Slide
Section 12.9: The Nonideal Transformer and its Equivalent Circuits cont.
Examples 12.6 and 12.7 cont.
Calculate the transformer’s voltage regulation and efficiency when it serves its rated KVA load at 0.8 lagging power factor
Note that |Vs| is 240 V. (rated) and Vs is chosen to be the reference phasor (at 0°)
The rated current (magnitude) is |Is| = |Srated|/|Vs| = 150 KVA/240 V. = 625 A.
The load’s power factor is 0.8 lagging so Is lags Vs by q = cos-1(0.8) » 36.87°
\ Is = 625/-36.87° A. so that KVL yields:
Es = 240/0°V. + (0.002 + j0.0045)W´625/-36.87° A. = 242.7/0.35° V.