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。
使用電(dian)(dian)能(neng)(neng)表(biao)時要注意(yi)，在低電(dian)(dian)壓(ya)（不超過500伏）和小電(dian)(dian)流（幾十安）的(de)情況下(xia)，電(dian)(dian)能(neng)(neng)表(biao)可直接接入(ru)電(dian)(dian)路進行(xing)測(ce)量。在高電(dian)(dian)壓(ya)或大電(dian)(dian)流的(de)情況下(xia)，電(dian)(dian)能(neng)(neng)表(biao)不能(neng)(neng)直接接入(ru)線路，需配合電(dian)(dian)壓(ya)互感器(qi)或電(dian)(dian)流互感器(qi)使用。
電能表的工作原理
當把電(dian)(dian)(dian)能表接入被測電(dian)(dian)(dian)路(lu)時(shi)(shi)，電(dian)(dian)(dian)流(liu)(liu)線圈(quan)和(he)電(dian)(dian)(dian)壓線圈(quan)中(zhong)(zhong)(zhong)(zhong)就有交(jiao)變(bian)電(dian)(dian)(dian)流(liu)(liu)流(liu)(liu)過(guo)，這兩個交(jiao)變(bian)電(dian)(dian)(dian)流(liu)(liu)分別在(zai)它們的(de)(de)(de)(de)鐵芯中(zhong)(zhong)(zhong)(zhong)產生交(jiao)變(bian)的(de)(de)(de)(de)磁(ci)(ci)通(tong)；交(jiao)變(bian)磁(ci)(ci)通(tong)穿過(guo)鋁(lv)(lv)(lv)盤(pan)(pan)，在(zai)鋁(lv)(lv)(lv)盤(pan)(pan)中(zhong)(zhong)(zhong)(zhong)感應出(chu)渦(wo)流(liu)(liu)；渦(wo)流(liu)(liu)又在(zai)磁(ci)(ci)場(chang)中(zhong)(zhong)(zhong)(zhong)受(shou)到力(li)的(de)(de)(de)(de)作(zuo)(zuo)用，從而(er)使鋁(lv)(lv)(lv)盤(pan)(pan)得到轉(zhuan)矩(ju)(ju)(ju)(ju)（主動(dong)(dong)力(li)矩(ju)(ju)(ju)(ju)）而(er)轉(zhuan)動(dong)(dong)。負載消耗(hao)的(de)(de)(de)(de)功(gong)率(lv)越大，通(tong)過(guo)電(dian)(dian)(dian)流(liu)(liu)線圈(quan)的(de)(de)(de)(de)電(dian)(dian)(dian)流(liu)(liu)越大，鋁(lv)(lv)(lv)盤(pan)(pan)中(zhong)(zhong)(zhong)(zhong)感應出(chu)的(de)(de)(de)(de)渦(wo)流(liu)(liu)也越大，使鋁(lv)(lv)(lv)盤(pan)(pan)轉(zhuan)動(dong)(dong)的(de)(de)(de)(de)力(li)矩(ju)(ju)(ju)(ju)就越大。即轉(zhuan)矩(ju)(ju)(ju)(ju)的(de)(de)(de)(de)大小(xiao)跟(gen)負載消耗(hao)的(de)(de)(de)(de)功(gong)率(lv)成正比(bi)(bi)。功(gong)率(lv)越大，轉(zhuan)矩(ju)(ju)(ju)(ju)也越大，鋁(lv)(lv)(lv)盤(pan)(pan)轉(zhuan)動(dong)(dong)也就越快。鋁(lv)(lv)(lv)盤(pan)(pan)轉(zhuan)動(dong)(dong)時(shi)(shi)，又受(shou)到**磁(ci)(ci)鐵產生的(de)(de)(de)(de)制(zhi)動(dong)(dong)力(li)矩(ju)(ju)(ju)(ju)的(de)(de)(de)(de)作(zuo)(zuo)用，制(zhi)動(dong)(dong)力(li)矩(ju)(ju)(ju)(ju)與主動(dong)(dong)力(li)矩(ju)(ju)(ju)(ju)方(fang)向(xiang)相反；制(zhi)動(dong)(dong)力(li)矩(ju)(ju)(ju)(ju)的(de)(de)(de)(de)大小(xiao)與鋁(lv)(lv)(lv)盤(pan)(pan)的(de)(de)(de)(de)轉(zhuan)速成正比(bi)(bi)，鋁(lv)(lv)(lv)盤(pan)(pan)轉(zhuan)動(dong)(dong)得越快，制(zhi)動(dong)(dong)力(li)矩(ju)(ju)(ju)(ju)也越大。當主動(dong)(dong)力(li)矩(ju)(ju)(ju)(ju)與制(zhi)動(dong)(dong)力(li)矩(ju)(ju)(ju)(ju)達到暫時(shi)(shi)平衡時(shi)(shi)，鋁(lv)(lv)(lv)盤(pan)(pan)將勻(yun)速轉(zhuan)動(dong)(dong)。負載所(suo)消耗(hao)的(de)(de)(de)(de)電(dian)(dian)(dian)能與鋁(lv)(lv)(lv)盤(pan)(pan)的(de)(de)(de)(de)轉(zhuan)數(shu)成正比(bi)(bi)。鋁(lv)(lv)(lv)盤(pan)(pan)轉(zhuan)動(dong)(dong)時(shi)(shi)，帶動(dong)(dong)計數(shu)器(qi)，把所(suo)消耗(hao)的(de)(de)(de)(de)電(dian)(dian)(dian)能指示(shi)出(chu)來。這就是(shi)電(dian)(dian)(dian)能表工作(zuo)(zuo)的(de)(de)(de)(de)簡單過(guo)程。
常(chang)用電能表的分類(lei)
（1）電能(neng)表(biao)按其使(shi)用的電路可分(fen)為直流電能(neng)表(biao)和(he)交(jiao)流電能(neng)表(biao)。交(jiao)流電能(neng)表(biao)按其相線(xian)又可分(fen)為單相電能(neng)表(biao)、三(san)(san)相三(san)(san)線(xian)電能(neng)表(biao)和(he)三(san)(san)相四(si)線(xian)電能(neng)表(biao)。
（2）電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)按其工作原理可分(fen)為電(dian)(dian)氣機械式(shi)(shi)電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)和電(dian)(dian)子式(shi)(shi)電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)（又稱(cheng)靜(jing)止式(shi)(shi)電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)、固態(tai)式(shi)(shi)電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)）。電(dian)(dian)氣機械式(shi)(shi)電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)用(yong)于交流電(dian)(dian)路(lu)作為普通(tong)的電(dian)(dian)能(neng)(neng)(neng)測量儀表(biao)(biao)(biao)，其中常用(yong)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）電能表按其結構(gou)可(ke)分(fen)為整(zheng)體(ti)(ti)式電能表和(he)分(fen)體(ti)(ti)式電能表。
（4）電(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)(biao)按(an)其用(yong)途可分為有功(gong)電(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)(biao)、無功(gong)電(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)(biao)、*大需量表(biao)(biao)(biao)(biao)、標準電(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)(biao)、復(fu)費率分時電(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)(biao)、預付(fu)費電(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)(biao)、損耗(hao)電(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)(biao)和多功(gong)能(neng)(neng)(neng)電(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)(biao)等。
（5）電能表按其準確度等級可分為普通安裝式電能表（0.2、0.5、1.0、2.0、3.0級）和攜帶式精密級電能表（0.01、0.02、0.05、0.1、0.2級）。
