有一对称三相负载,每相的等效电阻为30欧姆,等效感抗为40欧姆,绕组为星型连接,结于线电压为380伏的三相电源上,则：相电压 U = 380 / 根号3 = 220 V 每相阻抗 Z = （30*30+40*40）^0.5 = 50欧姆相电流 I = U / Z = 220 / 50 = 4.4 A线电流 I1 = 相电流I = 4.4 A有功功率 P = 3 * I * I * R = 3 * 4.4 * 4.4 * 30 = 1742.4 W无功功率 Q = 3 * I * I * x = 3 * 4.4 * 4.4 * 40 = 2323.2 ar视在功率 S = 3 * I * I * Z = 3 * 4.4 * 4.4 * 50 = 2904 va