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)表(biao)(biao)時(shi)要注(zhu)意，在低電(dian)(dian)壓（不超(chao)過(guo)500伏）和小電(dian)(dian)流(liu)（幾十(shi)安）的情(qing)況下(xia)，電(dian)(dian)能(neng)表(biao)(biao)可直(zhi)(zhi)接(jie)接(jie)入(ru)電(dian)(dian)路進(jin)行測(ce)量。在高電(dian)(dian)壓或大電(dian)(dian)流(liu)的情(qing)況下(xia)，電(dian)(dian)能(neng)表(biao)(biao)不能(neng)直(zhi)(zhi)接(jie)接(jie)入(ru)線路，需配合(he)電(dian)(dian)壓互感器或電(dian)(dian)流(liu)互感器使用。
電能表的工作原理
當把電(dian)(dian)能(neng)表接入被測電(dian)(dian)路(lu)時，電(dian)(dian)流線圈(quan)和電(dian)(dian)壓線圈(quan)中(zhong)(zhong)就(jiu)有交(jiao)變電(dian)(dian)流流過(guo)，這(zhe)兩個交(jiao)變電(dian)(dian)流分別在它們的(de)(de)(de)鐵芯中(zhong)(zhong)產(chan)生交(jiao)變的(de)(de)(de)磁(ci)通；交(jiao)變磁(ci)通穿過(guo)鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)，在鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)中(zhong)(zhong)感(gan)應出渦流；渦流又在磁(ci)場中(zhong)(zhong)受到力的(de)(de)(de)作(zuo)用，從而(er)使(shi)(shi)鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)得到轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)矩(ju)（主動(dong)(dong)(dong)(dong)力矩(ju)）而(er)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動(dong)(dong)(dong)(dong)。負載消(xiao)耗的(de)(de)(de)功率越大(da)，通過(guo)電(dian)(dian)流線圈(quan)的(de)(de)(de)電(dian)(dian)流越大(da)，鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)中(zhong)(zhong)感(gan)應出的(de)(de)(de)渦流也越大(da)，使(shi)(shi)鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動(dong)(dong)(dong)(dong)的(de)(de)(de)力矩(ju)就(jiu)越大(da)。即轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)矩(ju)的(de)(de)(de)大(da)小(xiao)跟負載消(xiao)耗的(de)(de)(de)功率成(cheng)正(zheng)比(bi)。功率越大(da)，轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)矩(ju)也越大(da)，鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動(dong)(dong)(dong)(dong)也就(jiu)越快(kuai)。鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動(dong)(dong)(dong)(dong)時，又受到**磁(ci)鐵產(chan)生的(de)(de)(de)制(zhi)動(dong)(dong)(dong)(dong)力矩(ju)的(de)(de)(de)作(zuo)用，制(zhi)動(dong)(dong)(dong)(dong)力矩(ju)與主動(dong)(dong)(dong)(dong)力矩(ju)方向相反(fan)；制(zhi)動(dong)(dong)(dong)(dong)力矩(ju)的(de)(de)(de)大(da)小(xiao)與鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)的(de)(de)(de)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)速成(cheng)正(zheng)比(bi)，鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動(dong)(dong)(dong)(dong)得越快(kuai)，制(zhi)動(dong)(dong)(dong)(dong)力矩(ju)也越大(da)。當主動(dong)(dong)(dong)(dong)力矩(ju)與制(zhi)動(dong)(dong)(dong)(dong)力矩(ju)達到暫(zan)時平衡時，鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)將勻速轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動(dong)(dong)(dong)(dong)。負載所消(xiao)耗的(de)(de)(de)電(dian)(dian)能(neng)與鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)的(de)(de)(de)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)數成(cheng)正(zheng)比(bi)。鋁(lv)(lv)(lv)(lv)(lv)(lv)盤(pan)(pan)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動(dong)(dong)(dong)(dong)時，帶(dai)動(dong)(dong)(dong)(dong)計數器(qi)，把所消(xiao)耗的(de)(de)(de)電(dian)(dian)能(neng)指示出來。這(zhe)就(jiu)是電(dian)(dian)能(neng)表工作(zuo)的(de)(de)(de)簡單(dan)過(guo)程。
常用(yong)電能(neng)表的分類
（1）電能表(biao)按其使(shi)用(yong)的電路可分為直流(liu)電能表(biao)和交流(liu)電能表(biao)。交流(liu)電能表(biao)按其相(xiang)線(xian)又(you)可分為單相(xiang)電能表(biao)、三(san)相(xiang)三(san)線(xian)電能表(biao)和三(san)相(xiang)四線(xian)電能表(biao)。
（2）電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)按(an)其工作原理可分為(wei)電(dian)(dian)氣(qi)(qi)機械式(shi)電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)和電(dian)(dian)子式(shi)電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)（又稱(cheng)靜止(zhi)式(shi)電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)、固態式(shi)電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)）。電(dian)(dian)氣(qi)(qi)機械式(shi)電(dian)(dian)能(neng)(neng)(neng)表(biao)(biao)(biao)用于(yu)交流電(dian)(dian)路(lu)作為(wei)普通的電(dian)(dian)能(neng)(neng)(neng)測量儀表(biao)(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(neng)表(biao)按其結構可分為整體式(shi)電能(neng)表(biao)和分體式(shi)電能(neng)表(biao)。
（4）電(dian)能(neng)(neng)表(biao)(biao)按其用(yong)途(tu)可分(fen)(fen)為有功電(dian)能(neng)(neng)表(biao)(biao)、無功電(dian)能(neng)(neng)表(biao)(biao)、*大需量表(biao)(biao)、標準電(dian)能(neng)(neng)表(biao)(biao)、復費率分(fen)(fen)時電(dian)能(neng)(neng)表(biao)(biao)、預付費電(dian)能(neng)(neng)表(biao)(biao)、損耗(hao)電(dian)能(neng)(neng)表(biao)(biao)和多功能(neng)(neng)電(dian)能(neng)(neng)表(biao)(biao)等。
（5）電能表按其準確(que)度等(deng)級(ji)(ji)可分為普通(tong)安裝式(shi)電能表（0.2、0.5、1.0、2.0、3.0級(ji)(ji)）和攜帶(dai)式(shi)精(jing)密(mi)級(ji)(ji)電能表（0.01、0.02、0.05、0.1、0.2級(ji)(ji)）。
