对无功功率物理意义的讨论

有功功率和无功功率是电工理论中非常重要的基本概念,有功功率物理意义明确,是瞬时功率在一个周期内的平均值,而无功功率概念模糊,正弦稳态电路中,一端口网络无功功率的值为端口电压有效值与电流有效值及电压与电流相位差的正弦函数三者的乘积,即Q=UIsinφ,有的教材将无功功率解释为网络内部与外部电源能量交换的最大规模,本文通过纯电阻、纯电感和纯电容电路,以及对RL与C并联电路的分析,证实对无功功率的这种解释是有歧义的.

DISCUSSION ON PHYSICAL SIGNIFICANCE OF REACTIVE POWER

Active power and reactive power are very important basic concepts in electrician theories.Physical significance of active power is definite,which is defined as the average of the instantaneous power in a period.While the concept of reactive power is vague.In the sine steady circuit,the value of reactive power of the one port network equals the product of the voltage effective value times the current effective value times the sine function of phase difference between voltage and current,that is Q=UIsinφ.In some textbooks,reactive power is explained as the largest power energy exchange between the internal and the external of network.In this paper,through analysis of pure resistive circuit,pure inductive circuit,and parallel circuit of RLand C,we prove that such an interpretation of reactive power is ambiguous.