PPT Slide
Section 12.9: The Nonideal Transformer and its Equivalent Circuits cont.
When unloaded, the winding currents are essentially zero since the load draws no current. Ergo, the only no-load power losses are core losses, which at rated voltage are 589 W.
So the total loss energy each day is:
2.18 KW´12 hours (full load) + 987 W.´8 hours (half load) + 589 W.´4 hours (no load) = 36.41 KWH \
All-day efficiency = [2040 KWH/(2076.41 KWH)] ´ 100% = 98.2%
Calculate the previous example’s all-day efficiency if it’s load schedule is as follows: Full-load at 0.8 lagging power factor for 12 hours, no-load for 4 hours and half-load at unity power factor for 8 hours