【微(wei)波(bo)爐(lu)原理(li)】微(wei)波(bo)爐(lu)的(de)工作(zuo)原理(li)圖(tu)解 微(wei)波(bo)爐(lu)的(de)電路圖(tu)分析

微波爐按(an)功能(neng)分(fen)為(wei)微(wei)(wei)(wei)波加(jia)熱(re)型(xing)(xing)和(he)微(wei)(wei)(wei)波燒(shao)烤型(xing)(xing)；按(an)控制類型(xing)(xing)分(fen)為(wei)機械(xie)型(xing)(xing)和(he)微(wei)(wei)(wei)電腦型(xing)(xing)。微(wei)(wei)(wei)波爐微(wei)(wei)(wei)波系統結構(gou)示意(yi)圖如右圖所示，其工作(zuo)原理如下：控制電路(lu)根據用戶設(she)置的(de)(de)火力，將(jiang)AC220V電壓(ya)(ya)(ya)(ya)加(jia)到(dao)高(gao)壓(ya)(ya)(ya)(ya)變(bian)壓(ya)(ya)(ya)(ya)器的(de)(de)初(chu)級，其次級輸出(chu)3V～4V和(he)1800V～2230V兩組交(jiao)流(liu)(liu)(liu)電壓(ya)(ya)(ya)(ya)。3V～4V交(jiao)流(liu)(liu)(liu)電壓(ya)(ya)(ya)(ya)直接給磁控管燈絲供電；1800V～2230V交(jiao)流(liu)(liu)(liu)電壓(ya)(ya)(ya)(ya)經高(gao)壓(ya)(ya)(ya)(ya)電容、高(gao)壓(ya)(ya)(ya)(ya)二極管倍壓(ya)(ya)(ya)(ya)整(zheng)流(liu)(liu)(liu)濾波后，變(bian)為(wei)3600V～4500V的(de)(de)負直流(liu)(liu)(liu)電壓(ya)(ya)(ya)(ya)，加(jia)到(dao)磁控管陰極。當(dang)磁控管具(ju)備燈絲電壓(ya)(ya)(ya)(ya)，且陽極（接地）與陰極之間的(de)(de)電壓(ya)(ya)(ya)(ya)差(cha)大(da)于(yu)3500V時，就產生(sheng)2450MHz超高(gao)頻電磁波，即微(wei)(wei)(wei)波，快速震動食(shi)品(pin)內的(de)(de)蛋白質、脂類、糖類及水等物質的(de)(de)分(fen)子，使之相互(hu)碰(peng)撞、擠壓(ya)(ya)(ya)(ya)、摩擦，重(zhong)新排(pai)列組合。簡而言之，微(wei)(wei)(wei)波爐是靠食(shi)品(pin)內部(bu)的(de)(de)摩擦生(sheng)熱(re)來進行烹(peng)調的(de)(de)。

磁(ci)(ci)控(kong)(kong)(kong)管發(fa)射(she)微(wei)波的(de)(de)強度（即功(gong)(gong)率）與陰陽(yang)極(ji)電(dian)壓(ya)(ya)(ya)差及發(fa)射(she)時(shi)間(jian)成正比(bi)。實際上，工廠是通過高(gao)(gao)壓(ya)(ya)(ya)變(bian)(bian)(bian)壓(ya)(ya)(ya)器的(de)(de)高(gao)(gao)壓(ya)(ya)(ya)輸出(chu)(chu)值(zhi)來設計微(wei)波的(de)(de)額(e)定輸出(chu)(chu)功(gong)(gong)率的(de)(de)。用戶設置火力，就是改變(bian)(bian)(bian)控(kong)(kong)(kong)制(zhi)電(dian)路(lu)給高(gao)(gao)壓(ya)(ya)(ya)變(bian)(bian)(bian)壓(ya)(ya)(ya)器提供(gong)AC220V電(dian)源的(de)(de)時(shi)間(jian)，從而控(kong)(kong)(kong)制(zhi)了烹調(diao)時(shi)微(wei)波爐的(de)(de)實際輸出(chu)(chu)功(gong)(gong)率。在最(zui)高(gao)(gao)火力擋時(shi)，控(kong)(kong)(kong)制(zhi)電(dian)路(lu)始終給高(gao)(gao)壓(ya)(ya)(ya)變(bian)(bian)(bian)壓(ya)(ya)(ya)器初級(ji)供(gong)電(dian)，磁(ci)(ci)控(kong)(kong)(kong)管連續發(fa)射(she)微(wei)波，此時(shi)輸出(chu)(chu)功(gong)(gong)率最(zui)大；而在非(fei)最(zui)高(gao)(gao)火力時(shi)，控(kong)(kong)(kong)制(zhi)電(dian)路(lu)則以30s為一個周期(qi)，間(jian)歇性(xing)給高(gao)(gao)壓(ya)(ya)(ya)變(bian)(bian)(bian)壓(ya)(ya)(ya)器初級(ji)供(gong)電(dian)，使磁(ci)(ci)控(kong)(kong)(kong)管間(jian)歇性(xing)發(fa)射(she)微(wei)波，微(wei)波爐平(ping)均輸出(chu)(chu)功(gong)(gong)率將低于(yu)最(zui)大功(gong)(gong)率。　　電(dian)路(lu)原理簡(jian)析(xi)

機械式微波爐的(de)電(dian)(dian)控(kong)部分(fen)(fen)(fen)主(zhu)要(yao)(yao)由(you)四(si)部分(fen)(fen)(fen)組(zu)成(cheng)，一是市電(dian)(dian)供給部分(fen)(fen)(fen)，由(you)電(dian)(dian)源(yuan)插(cha)頭，市電(dian)(dian)保險(xian)絲FUSE，開關和電(dian)(dian)線等(deng)組(zu)成(cheng)；二是升壓部分(fen)(fen)(fen)，主(zhu)要(yao)(yao)由(you)升壓變壓器T組(zu)成(cheng)；三(san)是整流部分(fen)(fen)(fen)，由(you)高壓保險(xian)絲H.V．FUSE，高壓二極管D，高壓電(dian)(dian)容器C等(deng)組(zu)成(cheng)；四(si)是微波產(chan)生部分(fen)(fen)(fen)，主(zhu)要(yao)(yao)由(you)磁(ci)控(kong)管和波導裝置(zhi)組(zu)成(cheng)，如上圖所示。

在(zai)該電路(lu)中一共有以下三個電流回路(lu)：

一(yi)是(shi)市電(dian)回路(lu)，220V交流(liu)(liu)電(dian)經保(bao)險(xian)絲、電(dian)機(ji)、升(sheng)壓(ya)(ya)變壓(ya)(ya)器初級后流(liu)(liu)回插(cha)座。二是(shi)燈絲回路(lu)，升(sheng)壓(ya)(ya)變壓(ya)(ya)器的一(yi)個(ge)次級繞(rao)組輸出約3V交流(liu)(liu)電(dian)，供給(gei)磁控管(guan)燈絲。只有燈絲加熱陰(yin)極，陰(yin)極才能(neng)發射電(dian)子。上(shang)面(mian)兩個(ge)回路(lu)流(liu)(liu)的是(shi)交流(liu)(liu)電(dian)。第三個(ge)回路(lu)是(shi)高(gao)壓(ya)(ya)回路(lu)，流(liu)(liu)的是(shi)高(gao)頻高(gao)壓(ya)(ya)脈動直流(liu)(liu)電(dian)。

1、220V市電回路

當關(guan)(guan)上爐門(men)后，定時(shi)器打開。S3被下(xia)(xia)門(men)鉤推開，呈開路狀態，在電(dian)路里不起(qi)作用，此(ci)時(shi)市電(dian)電(dian)路中的電(dian)流如(ru)下(xia)(xia)圖(tu)所示，干路電(dian)流標為I，各并聯(lian)支(zhi)路里電(dian)流標為i。干路里電(dian)流I回(hui)路如(ru)下(xia)(xia)：電(dian)源L→FUSE→第一閂鎖開關(guan)(guan)Sl→定時(shi)開關(guan)(guan)S4→五個并聯(lian)支(zhi)路(iL、il-i4)→第二閂鎖開關(guan)(guan)S2→熱繼電(dian)器S6→回(hui)到電(dian)源線N，則電(dian)流I=il,+il+i2+i3+i4。

【提示(shi)】（1）上述五(wu)個支路(lu)里(li)任一個短(duan)路(lu)，總電(dian)流就會增大，從(cong)而(er)出現燒保險管(guan)故障。其中(zhong)(zhong)，變(bian)壓器(qi)短(duan)路(lu)尤為常(chang)見。（2）在(zai)此(ci)電(dian)路(lu)中(zhong)(zhong)，干路(lu)上的(de)(de)元器(qi)件(jian)(jian)的(de)(de)連接(jie)多采用接(jie)插件(jian)(jian)，只要有一處斷(duan)開，總電(dian)流就為0，微(wei)波爐不工作。