變頻電(dian)(dian)機(ji)的(de)出現(xian)主(zhu)要(yao)解決普(pu)(pu)通電(dian)(dian)機(ji)在低(di)(di)速和高(gao)速運行的(de)一(yi)些問題(ti)，普(pu)(pu)通電(dian)(dian)機(ji)在低(di)(di)速運行是電(dian)(dian)機(ji)的(de)散熱(re)(re)問題(ti)和高(gao)速時電(dian)(dian)機(ji)軸承的(de)強度問題(ti)。普(pu)(pu)通電(dian)(dian)機(ji)的(de)散熱(re)(re)大多是空氣(qi)自冷(leng)式，電(dian)(dian)機(ji)的(de)散熱(re)(re)靠電(dian)(dian)機(ji)端部(bu)的(de)兩片(pian)葉(xie)輪(lun)的(de)攪動。當電(dian)(dian)機(ji)的(de)轉速較低(di)(di)的(de)時候，電(dian)(dian)機(ji)的(de)散熱(re)(re)就成了問題(ti)。
二次轉(zhuan)(zhuan)矩(ju)負載，在(zai)轉(zhuan)(zhuan)速(su)降(jiang)低(di)時(shi)(shi)(shi)，轉(zhuan)(zhuan)矩(ju)也降(jiang)低(di)，發熱量(liang)也降(jiang)低(di)，適合(he)選(xuan)用(yong)(yong)(yong)(yong)(yong)普(pu)通(tong)的(de)(de)電(dian)機(ji)(ji)用(yong)(yong)(yong)(yong)(yong)于(yu)(yu)變頻(pin)，但時(shi)(shi)(shi)間已不在(zai)低(di)于(yu)(yu)40%同步(bu)(bu)速(su)的(de)(de)情況(kuang)下使用(yong)(yong)(yong)(yong)(yong)。其他的(de)(de)負載，在(zai)60%同步(bu)(bu)速(su)及以(yi)上運行(xing)時(shi)(shi)(shi)，選(xuan)用(yong)(yong)(yong)(yong)(yong)普(pu)通(tong)的(de)(de)電(dian)機(ji)(ji)。在(zai)25%—60%同步(bu)(bu)速(su)運行(xing)時(shi)(shi)(shi)，選(xuan)用(yong)(yong)(yong)(yong)(yong)外(wai)部(bu)強(qiang)制冷(leng)卻籠性電(dian)動(dong)機(ji)(ji)，即變頻(pin)專用(yong)(yong)(yong)(yong)(yong)電(dian)機(ji)(ji)。當轉(zhuan)(zhuan)速(su)低(di)于(yu)(yu)25%同步(bu)(bu)速(su)時(shi)(shi)(shi)，選(xuan)用(yong)(yong)(yong)(yong)(yong)完全強(qiang)制冷(leng)卻電(dian)動(dong)機(ji)(ji)。即矢量(liang)專用(yong)(yong)(yong)(yong)(yong)電(dian)動(dong)機(ji)(ji)。
不(bu)(bu)同的(de)(de)變(bian)頻控(kong)制(zhi)(zhi)方式控(kong)制(zhi)(zhi)的(de)(de)速(su)(su)(su)度(du)(du)的(de)(de)速(su)(su)(su)度(du)(du)是(shi)不(bu)(bu)一樣的(de)(de)，采(cai)用(yong)(yong)U/F控(kong)制(zhi)(zhi)方式控(kong)制(zhi)(zhi)速(su)(su)(su)度(du)(du)的(de)(de)范圍(wei)(wei)是(shi)150—1470m/min；采(cai)用(yong)(yong)無速(su)(su)(su)度(du)(du)傳感(gan)器(qi)的(de)(de)矢(shi)量(liang)控(kong)制(zhi)(zhi)和(he)(he)直(zhi)接(jie)轉(zhuan)(zhuan)矩(ju)控(kong)制(zhi)(zhi)，控(kong)制(zhi)(zhi)速(su)(su)(su)度(du)(du)的(de)(de)范圍(wei)(wei)是(shi)60—1500m/min；采(cai)用(yong)(yong)速(su)(su)(su)度(du)(du)傳感(gan)器(qi)的(de)(de)矢(shi)量(liang)控(kong)制(zhi)(zhi)和(he)(he)直(zhi)接(jie)轉(zhuan)(zhuan)矩(ju)控(kong)制(zhi)(zhi)，控(kong)制(zhi)(zhi)速(su)(su)(su)度(du)(du)的(de)(de)范圍(wei)(wei)是(shi)5—1500m/min，在(zai)5m/min時(shi)運行的(de)(de)穩定性不(bu)(bu)太好。
