# My Doc

Topics: Root mean square, Power factor, AC power Pages: 4 (603 words) Published: July 23, 2009
TUTORIAL 1
AC Theory

1. An equipment draws from the supply system a 1000 kVA load with a 0.8 power factor lagging. Find the real and reactive power of the system. [800 W, 600 kvar]

2. In the power triangle of figures below, calculate the missing parameters; the reactive power (Q), real power (P) or apparent power (S).

[866 kW, -500 kvar, 577 W, 1.15 kVA]

3. For the given voltages and current below, calculate the a) complex power S, b) apparent power S, c) real power P and c) reactive power Q. Determine also whether the power factor obtained is leading or lagging.

i) V = 240(30(I = 5(60(
ii) V = 220((30(I = 5(20(
iii) V = 240(0(I = 5((20(
iv) V = 110(30(I = 8((20(

[1200(-30VA, 1200 VA, 1.04 kW, -600var, 0.866 leading]

4. An inductive load consisting of R and X in series feeding from a 2400-V rms supply absorbs 288 kW at a lagging power factor of 0.8. Determine R and X. [12.8 Ω, 9.6Ω]

5. An inductive load consisting of R and X in parallel feeding from a 2400-V rms supply absorbs 288 kW at a lagging power factor of 0.8. Determine R and X. [20 Ω, 26.7 Ω]

6. Two loads connected in parallel are supplied from a single-phase 240-V rms source. The two loads draw a total real power of 400 kW at a power factor of 0.8 lagging. One of the loads draws 120 kW at a power factor of 0.96 leading. Find the complex power of the other load. [436.6(50.1˚ kVA]

7. The load shown below consists of a resistance R in parallel with a capacitor of reactance X. The load is fed from a single-phase supply through a line of impedance 8.4 + j11.2 Ω. The rms voltage at the load terminal is 1200(0( V rms, and the load is taking 30 kVA at 0.8 power factor leading. a) Find the value of R and X

b) Determine the supply voltage V.

[60 Ω, 80 Ω, 1250(16.26˚ V]

8. Two impedances, Z1 = 0.8 + j5.6 Ω and Z2 = 8 ( j16 Ω, and a single-phase motor are connected in parallel across a 200- V rms, 60Hz...