【微波(bo)爐(lu)原理】微波(bo)爐(lu)的工作原理圖(tu)(tu)解(jie) 微波(bo)爐(lu)的電路圖(tu)(tu)分(fen)析(xi)

微波爐按功能分為微波(bo)加熱(re)(re)型和微波(bo)燒(shao)烤型；按控制類(lei)型分為機械型和微電(dian)(dian)(dian)(dian)(dian)腦型。微波(bo)爐(lu)微波(bo)系統結構示意圖如右圖所示，其(qi)工作原理如下：控制電(dian)(dian)(dian)(dian)(dian)路根據用戶(hu)設置的(de)火力，將AC220V電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)加到高壓(ya)(ya)(ya)變壓(ya)(ya)(ya)器的(de)初級，其(qi)次級輸出(chu)3V～4V和1800V～2230V兩組交(jiao)流電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。3V～4V交(jiao)流電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)直接給磁(ci)(ci)控管燈絲(si)供電(dian)(dian)(dian)(dian)(dian)；1800V～2230V交(jiao)流電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)經高壓(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)容、高壓(ya)(ya)(ya)二極(ji)(ji)管倍壓(ya)(ya)(ya)整(zheng)流濾波(bo)后(hou)，變為3600V～4500V的(de)負(fu)直流電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，加到磁(ci)(ci)控管陰極(ji)(ji)。當(dang)磁(ci)(ci)控管具備燈絲(si)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，且(qie)陽極(ji)(ji)（接地）與陰極(ji)(ji)之(zhi)間(jian)的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)差大于3500V時，就產生2450MHz超高頻電(dian)(dian)(dian)(dian)(dian)磁(ci)(ci)波(bo)，即微波(bo)，快速震動食(shi)品(pin)內的(de)蛋白(bai)質、脂類(lei)、糖類(lei)及(ji)水等物(wu)質的(de)分子，使之(zhi)相(xiang)互碰(peng)撞、擠壓(ya)(ya)(ya)、摩(mo)擦，重新排列組合(he)。簡而言之(zhi)，微波(bo)爐(lu)是(shi)靠食(shi)品(pin)內部的(de)摩(mo)擦生熱(re)(re)來進行烹調的(de)。

磁控管發射(she)微(wei)波(bo)的(de)強(qiang)度（即功(gong)(gong)(gong)率）與陰陽(yang)極電壓(ya)(ya)差(cha)及發射(she)時(shi)間(jian)成(cheng)正比。實(shi)際(ji)(ji)上，工廠是(shi)通(tong)過高(gao)(gao)(gao)(gao)壓(ya)(ya)變(bian)壓(ya)(ya)器的(de)高(gao)(gao)(gao)(gao)壓(ya)(ya)輸(shu)(shu)出(chu)值來設計微(wei)波(bo)的(de)額定(ding)輸(shu)(shu)出(chu)功(gong)(gong)(gong)率的(de)。用戶設置(zhi)火(huo)力(li)，就是(shi)改(gai)變(bian)控制(zhi)電路(lu)給高(gao)(gao)(gao)(gao)壓(ya)(ya)變(bian)壓(ya)(ya)器提供(gong)AC220V電源的(de)時(shi)間(jian)，從而(er)控制(zhi)了烹調時(shi)微(wei)波(bo)爐的(de)實(shi)際(ji)(ji)輸(shu)(shu)出(chu)功(gong)(gong)(gong)率。在(zai)最(zui)高(gao)(gao)(gao)(gao)火(huo)力(li)擋(dang)時(shi)，控制(zhi)電路(lu)始終(zhong)給高(gao)(gao)(gao)(gao)壓(ya)(ya)變(bian)壓(ya)(ya)器初級(ji)供(gong)電，磁控管連續發射(she)微(wei)波(bo)，此時(shi)輸(shu)(shu)出(chu)功(gong)(gong)(gong)率最(zui)大；而(er)在(zai)非最(zui)高(gao)(gao)(gao)(gao)火(huo)力(li)時(shi)，控制(zhi)電路(lu)則以(yi)30s為一個周期，間(jian)歇性給高(gao)(gao)(gao)(gao)壓(ya)(ya)變(bian)壓(ya)(ya)器初級(ji)供(gong)電，使磁控管間(jian)歇性發射(she)微(wei)波(bo)，微(wei)波(bo)爐平均(jun)輸(shu)(shu)出(chu)功(gong)(gong)(gong)率將低(di)于最(zui)大功(gong)(gong)(gong)率。　　電路(lu)原理簡(jian)析

機械式微波爐的(de)電(dian)(dian)(dian)控(kong)部(bu)分(fen)(fen)主要(yao)(yao)(yao)由(you)四(si)部(bu)分(fen)(fen)組(zu)成(cheng)(cheng)(cheng)，一是(shi)(shi)市電(dian)(dian)(dian)供給部(bu)分(fen)(fen)，由(you)電(dian)(dian)(dian)源插頭，市電(dian)(dian)(dian)保(bao)險絲FUSE，開(kai)關(guan)和電(dian)(dian)(dian)線等(deng)組(zu)成(cheng)(cheng)(cheng)；二是(shi)(shi)升(sheng)壓部(bu)分(fen)(fen)，主要(yao)(yao)(yao)由(you)升(sheng)壓變壓器(qi)T組(zu)成(cheng)(cheng)(cheng)；三是(shi)(shi)整流部(bu)分(fen)(fen)，由(you)高(gao)壓保(bao)險絲H.V．FUSE，高(gao)壓二極管D，高(gao)壓電(dian)(dian)(dian)容器(qi)C等(deng)組(zu)成(cheng)(cheng)(cheng)；四(si)是(shi)(shi)微波產生部(bu)分(fen)(fen)，主要(yao)(yao)(yao)由(you)磁控(kong)管和波導(dao)裝置組(zu)成(cheng)(cheng)(cheng)，如上圖所(suo)示。

在該(gai)電路中一(yi)共(gong)有以(yi)下三個(ge)電流(liu)回路：

一是(shi)(shi)市電(dian)(dian)回路，220V交流(liu)電(dian)(dian)經保險絲、電(dian)(dian)機、升壓(ya)變壓(ya)器初(chu)級(ji)后流(liu)回插座。二是(shi)(shi)燈(deng)絲回路，升壓(ya)變壓(ya)器的(de)一個(ge)次級(ji)繞組輸出(chu)約3V交流(liu)電(dian)(dian)，供給磁控管燈(deng)絲。只有燈(deng)絲加熱陰極，陰極才(cai)能發(fa)射電(dian)(dian)子。上面兩(liang)個(ge)回路流(liu)的(de)是(shi)(shi)交流(liu)電(dian)(dian)。第(di)三個(ge)回路是(shi)(shi)高(gao)壓(ya)回路，流(liu)的(de)是(shi)(shi)高(gao)頻高(gao)壓(ya)脈(mo)動直流(liu)電(dian)(dian)。

1、220V市電回路

當關(guan)上爐(lu)門(men)后，定時(shi)(shi)器打開(kai)。S3被下門(men)鉤推開(kai)，呈開(kai)路(lu)狀態，在電(dian)(dian)(dian)(dian)路(lu)里不(bu)起作用(yong)，此時(shi)(shi)市電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)路(lu)中(zhong)的電(dian)(dian)(dian)(dian)流(liu)如下圖(tu)所示，干路(lu)電(dian)(dian)(dian)(dian)流(liu)標為(wei)I，各并聯支(zhi)路(lu)里電(dian)(dian)(dian)(dian)流(liu)標為(wei)i。干路(lu)里電(dian)(dian)(dian)(dian)流(liu)I回路(lu)如下：電(dian)(dian)(dian)(dian)源L→FUSE→第一(yi)閂(shuan)鎖開(kai)關(guan)Sl→定時(shi)(shi)開(kai)關(guan)S4→五個(ge)并聯支(zhi)路(lu)(iL、il-i4)→第二閂(shuan)鎖開(kai)關(guan)S2→熱繼電(dian)(dian)(dian)(dian)器S6→回到電(dian)(dian)(dian)(dian)源線N，則電(dian)(dian)(dian)(dian)流(liu)I=il,+il+i2+i3+i4。

【提示】（1）上述五個(ge)支(zhi)路(lu)(lu)(lu)(lu)里任一個(ge)短(duan)路(lu)(lu)(lu)(lu)，總(zong)電流就會增大，從而出現(xian)燒(shao)保(bao)險(xian)管(guan)故障。其中，變壓器短(duan)路(lu)(lu)(lu)(lu)尤為(wei)常見。（2）在此電路(lu)(lu)(lu)(lu)中，干路(lu)(lu)(lu)(lu)上的(de)元器件的(de)連接多(duo)采用(yong)接插(cha)件，只要有一處斷開，總(zong)電流就為(wei)0，微波爐不工(gong)作。