并联电容前：有功功率 P1 = U*I* cosφ = 220*30*0.5 = 3300 W = 3.3 KW
无功功率 Q1 = U*I* sinφ = 220*30*(1-0.5^2)^0.5 = 5.72 Kvar
并联电容后：cosφ = 0.9 φ = 25.84tanφ = 0.484 Q2 = tanφ * P1 = 1.6 Kvar
电容量：Q1 - Q2 = 5.72 - 1.6 = 4.12 Kvar