【微(wei)波(bo)爐原理】微(wei)波(bo)爐的工作原理圖(tu)解 微(wei)波(bo)爐的電路圖(tu)分析

微波爐按(an)功(gong)能分為微(wei)(wei)波(bo)(bo)加熱型(xing)和微(wei)(wei)波(bo)(bo)燒烤型(xing)；按(an)控(kong)制類型(xing)分為機(ji)械(xie)型(xing)和微(wei)(wei)電(dian)(dian)(dian)腦(nao)型(xing)。微(wei)(wei)波(bo)(bo)爐微(wei)(wei)波(bo)(bo)系統結構示意圖(tu)如右圖(tu)所示，其(qi)工(gong)作(zuo)原理如下：控(kong)制電(dian)(dian)(dian)路根(gen)據用戶設置的火力(li)，將AC220V電(dian)(dian)(dian)壓(ya)(ya)加到高壓(ya)(ya)變(bian)壓(ya)(ya)器的初級(ji)，其(qi)次(ci)級(ji)輸出3V～4V和1800V～2230V兩組(zu)交流(liu)(liu)電(dian)(dian)(dian)壓(ya)(ya)。3V～4V交流(liu)(liu)電(dian)(dian)(dian)壓(ya)(ya)直接(jie)給磁(ci)控(kong)管(guan)燈絲供電(dian)(dian)(dian)；1800V～2230V交流(liu)(liu)電(dian)(dian)(dian)壓(ya)(ya)經高壓(ya)(ya)電(dian)(dian)(dian)容、高壓(ya)(ya)二極(ji)(ji)(ji)管(guan)倍(bei)壓(ya)(ya)整流(liu)(liu)濾(lv)波(bo)(bo)后，變(bian)為3600V～4500V的負直流(liu)(liu)電(dian)(dian)(dian)壓(ya)(ya)，加到磁(ci)控(kong)管(guan)陰極(ji)(ji)(ji)。當磁(ci)控(kong)管(guan)具備(bei)燈絲電(dian)(dian)(dian)壓(ya)(ya)，且陽極(ji)(ji)(ji)（接(jie)地）與陰極(ji)(ji)(ji)之間的電(dian)(dian)(dian)壓(ya)(ya)差大于3500V時，就產(chan)生2450MHz超高頻(pin)電(dian)(dian)(dian)磁(ci)波(bo)(bo)，即(ji)微(wei)(wei)波(bo)(bo)，快速震動食品內的蛋(dan)白質、脂類、糖類及水(shui)等物質的分子，使之相(xiang)互碰撞(zhuang)、擠壓(ya)(ya)、摩擦，重新排列組(zu)合。簡而(er)言(yan)之，微(wei)(wei)波(bo)(bo)爐是(shi)靠食品內部的摩擦生熱來進行烹調的。

磁(ci)控管發射微波的強度（即功(gong)(gong)(gong)率(lv)）與(yu)陰陽極電(dian)(dian)壓(ya)(ya)(ya)差及發射時(shi)(shi)(shi)間(jian)成正比。實(shi)際上(shang)，工廠是通過高(gao)壓(ya)(ya)(ya)變壓(ya)(ya)(ya)器的高(gao)壓(ya)(ya)(ya)輸(shu)出(chu)值來設計微波的額定輸(shu)出(chu)功(gong)(gong)(gong)率(lv)的。用戶設置火力，就是改變控制電(dian)(dian)路(lu)給高(gao)壓(ya)(ya)(ya)變壓(ya)(ya)(ya)器提供AC220V電(dian)(dian)源的時(shi)(shi)(shi)間(jian)，從而控制了烹調(diao)時(shi)(shi)(shi)微波爐的實(shi)際輸(shu)出(chu)功(gong)(gong)(gong)率(lv)。在最高(gao)火力擋時(shi)(shi)(shi)，控制電(dian)(dian)路(lu)始終(zhong)給高(gao)壓(ya)(ya)(ya)變壓(ya)(ya)(ya)器初(chu)級供電(dian)(dian)，磁(ci)控管連(lian)續發射微波，此時(shi)(shi)(shi)輸(shu)出(chu)功(gong)(gong)(gong)率(lv)最大(da)；而在非(fei)最高(gao)火力時(shi)(shi)(shi)，控制電(dian)(dian)路(lu)則以30s為(wei)一(yi)個周期，間(jian)歇性(xing)給高(gao)壓(ya)(ya)(ya)變壓(ya)(ya)(ya)器初(chu)級供電(dian)(dian)，使磁(ci)控管間(jian)歇性(xing)發射微波，微波爐平均輸(shu)出(chu)功(gong)(gong)(gong)率(lv)將(jiang)低(di)于最大(da)功(gong)(gong)(gong)率(lv)。　　電(dian)(dian)路(lu)原理簡(jian)析

機械式微波爐的電(dian)控(kong)部分(fen)主(zhu)要由(you)四部分(fen)組成(cheng)(cheng)，一是(shi)市(shi)電(dian)供給部分(fen)，由(you)電(dian)源插頭，市(shi)電(dian)保險(xian)絲FUSE，開(kai)關和電(dian)線等(deng)組成(cheng)(cheng)；二(er)是(shi)升壓部分(fen)，主(zhu)要由(you)升壓變壓器T組成(cheng)(cheng)；三是(shi)整流部分(fen)，由(you)高(gao)壓保險(xian)絲H.V．FUSE，高(gao)壓二(er)極(ji)管(guan)D，高(gao)壓電(dian)容器C等(deng)組成(cheng)(cheng)；四是(shi)微波產生部分(fen)，主(zhu)要由(you)磁控(kong)管(guan)和波導裝置組成(cheng)(cheng)，如上圖所示。

在該電路中一共(gong)有以下三個電流回路：

一(yi)是市電(dian)回路(lu)，220V交流(liu)(liu)電(dian)經保險(xian)絲(si)、電(dian)機、升(sheng)壓(ya)變(bian)壓(ya)器(qi)初級(ji)后流(liu)(liu)回插座。二是燈絲(si)回路(lu)，升(sheng)壓(ya)變(bian)壓(ya)器(qi)的(de)一(yi)個次級(ji)繞組輸(shu)出(chu)約3V交流(liu)(liu)電(dian)，供給磁控管燈絲(si)。只(zhi)有燈絲(si)加熱陰極(ji)，陰極(ji)才能發射電(dian)子。上面兩個回路(lu)流(liu)(liu)的(de)是交流(liu)(liu)電(dian)。第三個回路(lu)是高(gao)(gao)壓(ya)回路(lu)，流(liu)(liu)的(de)是高(gao)(gao)頻高(gao)(gao)壓(ya)脈動直流(liu)(liu)電(dian)。

1、220V市電回路

當關(guan)上爐門(men)(men)后，定時(shi)(shi)器打開。S3被(bei)下門(men)(men)鉤推開，呈(cheng)開路(lu)狀態，在電(dian)(dian)路(lu)里(li)不(bu)起作用，此時(shi)(shi)市電(dian)(dian)電(dian)(dian)路(lu)中(zhong)的電(dian)(dian)流(liu)(liu)如(ru)(ru)下圖所(suo)示，干(gan)路(lu)電(dian)(dian)流(liu)(liu)標(biao)為I，各并聯支(zhi)路(lu)里(li)電(dian)(dian)流(liu)(liu)標(biao)為i。干(gan)路(lu)里(li)電(dian)(dian)流(liu)(liu)I回(hui)路(lu)如(ru)(ru)下：電(dian)(dian)源L→FUSE→第(di)一閂(shuan)鎖開關(guan)Sl→定時(shi)(shi)開關(guan)S4→五個并聯支(zhi)路(lu)(iL、il-i4)→第(di)二(er)閂(shuan)鎖開關(guan)S2→熱繼(ji)電(dian)(dian)器S6→回(hui)到電(dian)(dian)源線(xian)N，則電(dian)(dian)流(liu)(liu)I=il,+il+i2+i3+i4。

【提示】（1）上述五個支路(lu)里任一(yi)個短(duan)路(lu)，總電流就會增大，從而出(chu)現燒保險(xian)管故障。其(qi)中，變壓器(qi)短(duan)路(lu)尤為常見(jian)。（2）在此電路(lu)中，干路(lu)上的(de)(de)元器(qi)件的(de)(de)連接多采(cai)用接插件，只要有(you)一(yi)處斷(duan)開，總電流就為0，微波(bo)爐不工(gong)作(zuo)。