EEN-101: Introduction to Electrical Engineering
Tutorial-4
1. A balanced Δ supply with Vab = 440<150 V, feeds a star-connected load per phase impedance of (12+j15)
Ω. Find the three-line currents. Ans: IA = 13.224<-66.340 A,IB= 13.224<173.660 A, IC = 13.224<53.660 A
2. If the load is now delta-connected, find the phase and line currents.
Ans : IAB = 22.906< -36.340 A, IBC = 22.906< -156.340 A, ICA = 22.906< 83.6590 A, IA = 39.674< -66.340 A
3. A balanced Y-connected load with a phase impedance of (40 + j 25) Ω is supplied by a balanced positive,
sequence delta-connected source with a line voltage of 210 V. Calculate the phase currents. Use Vab as
a reference. Ans : IA = 2.57<-620 A
4. A positive-sequence, balanced delta-connected source supplies a balanced delta-connected load. If the
impedance per phase of the load is 18+j 12 Ω and IA is 9.609<350 A. Find IAB and VAB. Ans : IAB = 5.548<650 A,
VAB = 120<98.690 V.
5. For the circuit shown below, find the line currents. Ans: IA = 6.81<-21.80 A
6. A balanced three-phase three-wire system has a line voltage of 500 V. Two balanced Y-connected loads
are connected in parallel to the supply. One load has a per-phase impedance of 7- j 2 Ω, and the other
has 4 + j 2 Ω per-phase impedance. Calculate the three-line currents. Ans : IA = 97.558<-40.620A
7. Find the line current IB and the phase voltage VAN for the circuit.
Ans : IB = 8.547<-91.270 A; VAN = 100.9409< 60.86850 V