1、通過觀察變壓器的外貌來檢查其是否有明顯異常現象。如線圈引線是否斷裂，脫焊，絕緣材料是否有燒焦痕跡，鐵心緊固螺桿是否有松動，硅鋼片有無銹蝕，繞組線圈是否有外露等。
2、絕緣性測試(shi)。用(yong)(yong)萬(wan)用(yong)(yong)表(biao)(biao)R×10k擋分別測量鐵心(xin)與(yu)初級，初級與(yu)各次(ci)級、鐵心(xin)與(yu)各次(ci)級、靜電(dian)屏蔽層與(yu)衩次(ci)級、次(ci)級各繞組間(jian)的(de)電(dian)阻值，萬(wan)用(yong)(yong)表(biao)(biao)指針均應(ying)指在無窮大(da)位置不動。否則，說明變壓器絕緣性能不良。
3、線圈通斷(duan)的檢測(ce)。將萬用(yong)表置于R×1擋，土工布測試(shi)中，若(ruo)某個繞組的電阻值為(wei)無窮大，則說(shuo)明此繞組有斷路(lu)性故障(zhang)。
4、判別初(chu)、次級(ji)線圈。電源變壓器初(chu)級(ji)引腳(jiao)和(he)次級(ji)引腳(jiao)一般(ban)都是分別從兩側引出的(de)，并(bing)且初(chu)級(ji)繞(rao)(rao)組(zu)多標(biao)有220V字(zi)樣，次級(ji)繞(rao)(rao)組(zu)則標(biao)出額定電壓值(zhi)，如15V、24V、35V等。再根(gen)據這些標(biao)記(ji)進行(xing)識別。
5、空載(zai)電流的(de)檢測。
a、直(zhi)接(jie)測(ce)量法。將次(ci)級所有繞(rao)組全部開(kai)路，把萬(wan)用表置于交流(liu)電流(liu)擋(dang)(500mA，串入(ru)初級繞(rao)組。當初級繞(rao)組的插頭插入(ru)220V交流(liu)市電時，萬(wan)用表所指示的便是空載電流(liu)值(zhi)。此(ci)值(zhi)不(bu)應大于變壓器(qi)滿載電流(liu)的10%～20%。一般常見電子設備電源變壓器(qi)的正常空載電流(liu)應在100mA左(zuo)右。如果(guo)超出太多，則說明變壓器(qi)有短路性故障。
b、間(jian)接(jie)測(ce)(ce)量(liang)法(fa)。在變(bian)壓(ya)(ya)(ya)器的初(chu)級(ji)(ji)繞(rao)組(zu)中串聯(lian)一個10?/5W的電(dian)(dian)(dian)阻，次級(ji)(ji)仍全部空(kong)(kong)載(zai)(zai)。把萬用(yong)表(biao)(biao)撥至交(jiao)流電(dian)(dian)(dian)壓(ya)(ya)(ya)擋(dang)。加(jia)電(dian)(dian)(dian)后，用(yong)兩(liang)(liang)表(biao)(biao)筆測(ce)(ce)出電(dian)(dian)(dian)阻R兩(liang)(liang)端的電(dian)(dian)(dian)壓(ya)(ya)(ya)降U，然后用(yong)歐(ou)姆(mu)定律算出空(kong)(kong)載(zai)(zai)電(dian)(dian)(dian)流I空(kong)(kong)，即I空(kong)(kong)=U/R。F?空(kong)(kong)載(zai)(zai)電(dian)(dian)(dian)壓(ya)(ya)(ya)的檢測(ce)(ce)。將(jiang)電(dian)(dian)(dian)源變(bian)壓(ya)(ya)(ya)器的初(chu)級(ji)(ji)接(jie)220V市電(dian)(dian)(dian)，用(yong)萬用(yong)表(biao)(biao)交(jiao)流電(dian)(dian)(dian)壓(ya)(ya)(ya)接(jie)依次測(ce)(ce)出各(ge)繞(rao)組(zu)的空(kong)(kong)載(zai)(zai)電(dian)(dian)(dian)壓(ya)(ya)(ya)值(zhi)(zhi)(U21、U22、U23、U24)應符合要求(qiu)值(zhi)(zhi)，允許誤差范(fan)圍(wei)一般為：高壓(ya)(ya)(ya)繞(rao)組(zu)≤±10%，低壓(ya)(ya)(ya)繞(rao)組(zu)≤±5%，帶中心抽頭的兩(liang)(liang)組(zu)對稱(cheng)繞(rao)組(zu)的電(dian)(dian)(dian)壓(ya)(ya)(ya)差應≤±2%。
6、一(yi)般小(xiao)功率電源變壓(ya)器允(yun)許溫升為40℃～50℃，如果所用(yong)絕(jue)緣(yuan)材料質量較好，允(yun)許溫升還(huan)可提高。
7、檢(jian)測判(pan)別各(ge)(ge)繞組(zu)的同名端(duan)。在使用電源(yuan)變(bian)壓器(qi)時，有(you)時為了得到所(suo)需的次級電壓，可將兩(liang)個或多個次級繞組(zu)串(chuan)聯起(qi)來使用。采用串(chuan)聯法使用電源(yuan)變(bian)壓器(qi)時，參加串(chuan)聯的各(ge)(ge)繞組(zu)的同名端(duan)必(bi)須(xu)正(zheng)確連接，不(bu)能搞錯。否則，變(bian)壓器(qi)不(bu)能正(zheng)常工作。
8、電(dian)(dian)源(yuan)變(bian)(bian)(bian)壓(ya)器(qi)(qi)(qi)短(duan)(duan)(duan)路(lu)性故(gu)(gu)障的綜合(he)檢測判(pan)別(bie)。電(dian)(dian)源(yuan)變(bian)(bian)(bian)壓(ya)器(qi)(qi)(qi)發(fa)(fa)生短(duan)(duan)(duan)路(lu)性故(gu)(gu)障后的主要癥狀是發(fa)(fa)熱嚴(yan)重和次級繞(rao)組輸出電(dian)(dian)壓(ya)失(shi)常(chang)。通(tong)常(chang)，線圈(quan)內(nei)部匝(za)間(jian)短(duan)(duan)(duan)路(lu)點越(yue)多，短(duan)(duan)(duan)路(lu)電(dian)(dian)流(liu)(liu)就越(yue)大(da)，而變(bian)(bian)(bian)壓(ya)器(qi)(qi)(qi)發(fa)(fa)熱就越(yue)嚴(yan)重。檢測判(pan)斷電(dian)(dian)源(yuan)變(bian)(bian)(bian)壓(ya)器(qi)(qi)(qi)是否有(you)短(duan)(duan)(duan)路(lu)性故(gu)(gu)障的簡單方法是測量空載(zai)電(dian)(dian)流(liu)(liu)(測試方法前(qian)面已(yi)經介紹(shao))。存在(zai)(zai)短(duan)(duan)(duan)路(lu)故(gu)(gu)障的變(bian)(bian)(bian)壓(ya)器(qi)(qi)(qi)，其空載(zai)電(dian)(dian)流(liu)(liu)值(zhi)將(jiang)遠大(da)于滿載(zai)電(dian)(dian)流(liu)(liu)的10%。當短(duan)(duan)(duan)路(lu)嚴(yan)重時(shi)，變(bian)(bian)(bian)壓(ya)器(qi)(qi)(qi)在(zai)(zai)空載(zai)加電(dian)(dian)后幾十秒鐘之內(nei)便(bian)會迅(xun)速(su)發(fa)(fa)熱，用手(shou)觸摸鐵心會有(you)燙(tang)手(shou)的感覺(jue)。此時(shi)不用測量空載(zai)電(dian)(dian)流(liu)(liu)便(bian)可斷定變(bian)(bian)(bian)壓(ya)器(qi)(qi)(qi)有(you)短(duan)(duan)(duan)路(lu)點存在(zai)(zai)。
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