An Unforgetaable Moment in My Life

1. Three similar coils each having series resistance of 20Ω and capacitance 100μF are
connected in star to a 3-phase, 400V, 50 Hz balanced supply. Find the line current,
power factor, total kVA and total kW.
2. A star connected three-phase load draws a current of 20A at a lagging p.f. of 0.9 from a
balanced 440V, 50 Hz supply. Find the circuit elements in each phase if the elements are
connected in series.
3. For a three-phase delta connected load, each phase of which has series resistance of 8Ω
and reactance of 6Ω is supplied from a star connected balanced system having a phase
voltage of 230V. Calculate
(a) Magnitude of the phase current of the load and the supply system
(b) Active power taken by the load and the power actor of the load.
4. Three impedances ZA = 6 00, ZB = 6 300 and ZC = 5 450 are connected in star.
The phase currents are IA = 20 1000, IB = 10 -500 and IC. Find the voltage drops across
the three impedances of ZA, ZB, and ZC. Assume phasor sum of IA, IB and IC as zero.
5. A three phase 230V load has a power factor of 0.7. Two wattmeters are connected to
measure the power which shows the input to be 10kW. Find the reading of each
wattmeter.
6. In a balanced three phase 200V circuit, the line current is 115.5 A. When the power is
measured by two-wattmeter method one of the instruments reads 20kW and the other
zero. What is the power factor of the load?