電能表是用來測量電能的儀表，又稱電度表、火表、千瓦小時表，指測量各種電學量的儀表。
使用(yong)電(dian)(dian)能表時要注意，在(zai)低電(dian)(dian)壓（不(bu)超(chao)過(guo)500伏）和小電(dian)(dian)流（幾十安）的情況下(xia)，電(dian)(dian)能表可(ke)直接接入電(dian)(dian)路進行測量。在(zai)高電(dian)(dian)壓或大電(dian)(dian)流的情況下(xia)，電(dian)(dian)能表不(bu)能直接接入線路，需配合電(dian)(dian)壓互感(gan)器或電(dian)(dian)流互感(gan)器使用(yong)。
電能表的工作原理
當把電(dian)(dian)能(neng)表(biao)接入被測電(dian)(dian)路時，電(dian)(dian)流線圈和電(dian)(dian)壓線圈中就(jiu)有交變(bian)(bian)電(dian)(dian)流流過(guo)，這兩個交變(bian)(bian)電(dian)(dian)流分(fen)別在它們的(de)(de)鐵芯(xin)中產生(sheng)交變(bian)(bian)的(de)(de)磁通；交變(bian)(bian)磁通穿過(guo)鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)，在鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)中感應出渦(wo)流；渦(wo)流又在磁場(chang)中受到(dao)力(li)的(de)(de)作用，從而(er)使(shi)鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)得(de)到(dao)轉(zhuan)矩(ju)（主動(dong)(dong)(dong)(dong)(dong)力(li)矩(ju)）而(er)轉(zhuan)動(dong)(dong)(dong)(dong)(dong)。負(fu)載(zai)(zai)消耗的(de)(de)功率越(yue)(yue)(yue)大(da)(da)(da)，通過(guo)電(dian)(dian)流線圈的(de)(de)電(dian)(dian)流越(yue)(yue)(yue)大(da)(da)(da)，鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)中感應出的(de)(de)渦(wo)流也(ye)越(yue)(yue)(yue)大(da)(da)(da)，使(shi)鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)轉(zhuan)動(dong)(dong)(dong)(dong)(dong)的(de)(de)力(li)矩(ju)就(jiu)越(yue)(yue)(yue)大(da)(da)(da)。即轉(zhuan)矩(ju)的(de)(de)大(da)(da)(da)小跟負(fu)載(zai)(zai)消耗的(de)(de)功率成(cheng)正比。功率越(yue)(yue)(yue)大(da)(da)(da)，轉(zhuan)矩(ju)也(ye)越(yue)(yue)(yue)大(da)(da)(da)，鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)轉(zhuan)動(dong)(dong)(dong)(dong)(dong)也(ye)就(jiu)越(yue)(yue)(yue)快。鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)轉(zhuan)動(dong)(dong)(dong)(dong)(dong)時，又受到(dao)**磁鐵產生(sheng)的(de)(de)制(zhi)(zhi)(zhi)動(dong)(dong)(dong)(dong)(dong)力(li)矩(ju)的(de)(de)作用，制(zhi)(zhi)(zhi)動(dong)(dong)(dong)(dong)(dong)力(li)矩(ju)與(yu)主動(dong)(dong)(dong)(dong)(dong)力(li)矩(ju)方向相(xiang)反；制(zhi)(zhi)(zhi)動(dong)(dong)(dong)(dong)(dong)力(li)矩(ju)的(de)(de)大(da)(da)(da)小與(yu)鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)的(de)(de)轉(zhuan)速成(cheng)正比，鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)轉(zhuan)動(dong)(dong)(dong)(dong)(dong)得(de)越(yue)(yue)(yue)快，制(zhi)(zhi)(zhi)動(dong)(dong)(dong)(dong)(dong)力(li)矩(ju)也(ye)越(yue)(yue)(yue)大(da)(da)(da)。當主動(dong)(dong)(dong)(dong)(dong)力(li)矩(ju)與(yu)制(zhi)(zhi)(zhi)動(dong)(dong)(dong)(dong)(dong)力(li)矩(ju)達到(dao)暫(zan)時平衡時，鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)將勻(yun)速轉(zhuan)動(dong)(dong)(dong)(dong)(dong)。負(fu)載(zai)(zai)所消耗的(de)(de)電(dian)(dian)能(neng)與(yu)鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)的(de)(de)轉(zhuan)數(shu)(shu)成(cheng)正比。鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)(pan)轉(zhuan)動(dong)(dong)(dong)(dong)(dong)時，帶(dai)動(dong)(dong)(dong)(dong)(dong)計數(shu)(shu)器，把所消耗的(de)(de)電(dian)(dian)能(neng)指示出來(lai)。這就(jiu)是電(dian)(dian)能(neng)表(biao)工作的(de)(de)簡(jian)單過(guo)程。
常用電(dian)能(neng)表的分類
（1）電(dian)(dian)(dian)能(neng)表(biao)(biao)按其使用的電(dian)(dian)(dian)路可分(fen)為直流(liu)(liu)電(dian)(dian)(dian)能(neng)表(biao)(biao)和交流(liu)(liu)電(dian)(dian)(dian)能(neng)表(biao)(biao)。交流(liu)(liu)電(dian)(dian)(dian)能(neng)表(biao)(biao)按其相線(xian)又可分(fen)為單相電(dian)(dian)(dian)能(neng)表(biao)(biao)、三相三線(xian)電(dian)(dian)(dian)能(neng)表(biao)(biao)和三相四線(xian)電(dian)(dian)(dian)能(neng)表(biao)(biao)。
（2）電(dian)能(neng)(neng)表(biao)(biao)按其工作(zuo)原理可(ke)分為電(dian)氣(qi)機(ji)械(xie)(xie)式(shi)電(dian)能(neng)(neng)表(biao)(biao)和(he)電(dian)子(zi)式(shi)電(dian)能(neng)(neng)表(biao)(biao)（又稱靜止式(shi)電(dian)能(neng)(neng)表(biao)(biao)、固態式(shi)電(dian)能(neng)(neng)表(biao)(biao)）。電(dian)氣(qi)機(ji)械(xie)(xie)式(shi)電(dian)能(neng)(neng)表(biao)(biao)用于(yu)交流電(dian)路作(zuo)為普(pu)通(tong)的電(dian)能(neng)(neng)測量儀表(biao)(biao)，其中常用的是感應型電能表。電子式電能表可分為全電子式電能表和機電式電能表。
（3）電能表(biao)按其結構(gou)可分(fen)為整體式電能表(biao)和分(fen)體式電能表(biao)。
（4）電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)按其用(yong)途可分為有功(gong)電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)、無功(gong)電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)、*大需量(liang)表(biao)(biao)(biao)、標準電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)、復費率分時電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)、預(yu)付費電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)、損耗電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)和多功(gong)能(neng)電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)等(deng)。
（5）電(dian)能表按其(qi)準確度等(deng)級(ji)可分為普通安裝式電(dian)能表（0.2、0.5、1.0、2.0、3.0級(ji)）和攜帶(dai)式精密級(ji)電(dian)能表（0.01、0.02、0.05、0.1、0.2級(ji)）。
