Problem 97-3
Source: Example 2-56 - page 189 -
SAHDEV, S. K. - Book: Electrical Machines - 1st edition - Cambridge University Press - 2018.
Let two single-phase transformers be connected in parallel supplying a current of 1,000 A to a load that has
PF = 0.8 lagging. For each transformer, the secondary EMF in open circuit is 3,300 V. The secondary impedances are 0.1 + j0.2
and 0.05 + j0.4, respectively.
a) Calculate the current supplied by each transformer to the load.
b) Calculate the real power delivered by each transformer.
Solution of the Problema 97-3
Let's take the secondary terminal voltage as a reference, that is, VL = 3,300 ∠ 0° V. Thus, the load current will be IL = 1,000 ∠ -36.7° V, since FP = 0.8. Now, let's express the internal impedances of the transformers in their polar form, as well as the sum of the impedances.
The power factors are lagging because the angles are negative.
To verify our results, we can calculate the sum of the currents and obtain the value of IL. Thus:
