江蘇春晨電纜有限公司生產JH JEH電機引接線 春晨電纜，

純電感不消耗電能，它只與電源不斷地進行能量的交換。

Pure inductance does not consume electric energy, it only exchanges energy with power supply continuously.

電感的平均功率為：

The average power of the inductor is:

電感的平均功率計算公式

Calculation formula of average power of inductance

平均功率為零只說明電感不消耗有功功率，并不說明電感中沒有功率，電感與電源之間有能量交換，所以瞬時功率并不等于零。瞬時功率的大值即UI的乘積叫做無功功率，用符號QL表示，它反映了電感與電源交換能量的大規模。

If the average power is zero, it only means that the inductor does not consume active power, and it does not mean that there is no power in the inductor, and there is energy exchange between the inductor and the power supply, so the instantaneous power is not equal to zero. The maximum value of instantaneous power, i.e. the product of UI, is called reactive power, which is represented by symbol QL. It reflects the maximum scale of energy exchange between inductance and power supply.

電感無功功率計算公式

Calculation formula of inductive reactive power

工程上的變壓器、電動機都是通過電感線圈與電源進行電能和磁能轉換而工作的，但由電源提供無功功率，所以無功功率是電感元件工作時要的功率，不能理解為沒有用的功率。

In engineering, transformers and motors work by converting electric energy and magnetic energy between inductance coil and power supply, but reactive power must be provided by power supply, so reactive power is the necessary power when inductance element works, which cannot be understood as useless power.

算一算

add up

題：電感線圈的電感L=1H，接到電壓為u=220√2 sin（314t+60°）V的電源上，求流過電感的電流i和無功功率QL。

Title: the inductance of the inductance coil is L = 1H, connected to the power supply with the voltage of u = 220 √ 2Sin (314T + 60 °) V, and the current I and reactive power QL flowing through the inductance are calculated.

解：電壓的有效值相量為：

Solution: the effective value phasor of voltage is:

相量表示

Phasor representation

計算電感電路

Calculated inductance circuit

電容元件的交流電路

AC circuit of capacitor

如下圖所示的交流電路中，電容元件C認為是理想線性元件，其電流、電壓的參考方向已標在圖中。

In the AC circuit as shown in the figure below, capacitor element C is considered as an ideal linear element, and its reference direction of current and voltage has been marked in the figure.

電容元件的交流電路

AC circuit of capacitor

電流與電壓的關系

Relationship between current and voltage

當加在電容兩端的電壓為u=Umsinωt=U√2sinωt時，并以u為參考量，由前文《電路中的無源元件：電阻、電容和電感》中的下式：JH JEH電機引接線 春晨電纜

When the voltage applied to both ends of the capacitor is u = umsin ω t = u √ 2Sin ω T, and u is taken as the reference quantity, the following formula is given in the previous passive components in the circuit: resistance, capacitance and inductance:

電流電容的關系

Relationship between current and capacitance

可得電容電路的電流為：

The current of the available capacitance circuit is:

電容電路的電流公式

Current formula of capacitor circuit

由上式可見，電容上電流與電壓是同頻率的正弦量；電流與電壓的大小關系為

It can be seen from the above formula that the current and voltage on the capacitor are sinusoidal quantities of the same frequency; the relationship between the current and voltage is