電機(jī)啟動(dòng)型熱敏電阻器
馬達(dá)啟動(dòng)用正溫度系數(shù)熱敏電阻器,只要用于電冰箱、空調(diào)馬達(dá)啟動(dòng)、空調(diào)變頻機(jī)啟動(dòng)、馬達(dá)過熱保護(hù)等。
工作原理:馬達(dá)啟動(dòng)器是利用PTC陶瓷的電流-時(shí)間特性,當(dāng)電壓施加于PTCR時(shí),開始有大電流I流過,經(jīng)過一定時(shí)間ts后,隨著PTCR溫度的升高,電阻值迅速增大,導(dǎo)致電流也急劇下降,這段時(shí)間ts可以從0.1s到幾秒,其值取決于PTCR的熱容量、電阻值、熱耗散條件、負(fù)載電阻及工作電壓,當(dāng)外電壓撤銷時(shí),PTCR將冷卻至常溫電阻值。利用這個(gè)原理,在家用電冰箱和空調(diào)機(jī)等電器馬達(dá)啟動(dòng)上得到了廣泛的使用。應(yīng)該說明,當(dāng)使用PTCR的延遲性能時(shí),如果要重復(fù)同一延遲時(shí)間,應(yīng)間隔一定時(shí)間tr(即所謂的恢復(fù)時(shí)間),使PTCR恢復(fù)到原始狀態(tài)溫度,所以應(yīng)避免立即重復(fù)動(dòng)作,否則PTCR不能提供持續(xù)的大電流,使壓縮機(jī)無法正常啟動(dòng)工作,會導(dǎo)致壓縮機(jī)燒毀。
電機(jī)在啟動(dòng)時(shí),要克服本身的慣性,同時(shí)還要克服負(fù)載的反作用力(如冰箱壓縮機(jī)啟動(dòng)時(shí)必須克服制冷劑的反作用力),因此電機(jī)啟動(dòng)時(shí)需要較大的電流和轉(zhuǎn)矩。當(dāng)轉(zhuǎn)動(dòng)正常后,為了節(jié)約能源,需要的轉(zhuǎn)矩又要大幅度下降。給電機(jī)加一組輔助線圈,只在啟動(dòng)時(shí)工作,正常后它就斷開。將PTC熱敏電阻串聯(lián)在啟動(dòng)輔助線圈,啟動(dòng)后PTC熱敏電阻進(jìn)入高阻態(tài)切斷輔助線圈,正好可以達(dá)到這種效果.
產(chǎn)品優(yōu)勢:采用帶有PTCR的啟動(dòng)電路具有經(jīng)濟(jì)、可靠、電路簡單等特點(diǎn),優(yōu)于過去的重錘式啟動(dòng)電路,它具有無觸點(diǎn)、低噪聲、高可靠、長壽命等特點(diǎn)。
PTCThermistorsforMotor-Starting
Applications
Motor-startingPTCThermistorsaremainlyusedinfridgeandair-conditionermotor-starting,air-conditionertransducer-starting,motorover-heatingprotection.
WorkingTheories
Motor-starterisamachinethatmakesuseofthePTCpotterycurrent-timefeature.WhenPTCRisputonbypressure,theheavycurrentbeginstopassthrough,andaftercertaintime,withtheincreasingofthePTCtemperature,resistancevaluegoesupsharplyandcausecurrenttofalldownsuddenly.Duringthistime,tscanchangefrom0.1stoseveralseconds.ThespecifictimedependsonPTCR sheatingcapacity,resistancevalue,heatingdissipationcondition,overloadedresistanceandoperatingvoltage.Whentheouterelectricitypressureretreats,PTCwillbecomecoolandaltertonormalresistance.Makinguseofthistheory,PTCisappliedextensivelyinhouseholdrefrigeratorandair-conditionermotor-starterandsoon.Onepointshouldbenoticedthatwhenusingthedelay-timefeatureofPTC,weshouldmakethePTCrecovertoitsoriginaltemperatureeverycertaintimetr(Thatiswhatwecalledrecoveringtime).Sosuddenrepeatedmovementsshouldbeavoided,otherwisePTCcannotprovideconstantheavycurrent,andthecompressorcannotstartorworknormally,whichwillcausethecompressorburnt.
Whentheelectricitymotorisbeingstarted,ithastoovercomeitsinertiaandthecounterforceofloading(eg:Itscounterforcemustbeovercomewhenrefrigeratorcompressorstarts),sostartingtheelectricitymotorneedsrelativelyheavycurrentandtorque.Whenitrunsnormally,andthetorqueneededhastobebroughtdowntosaveenergy.Givemotorelectricityacircleassistantloop,anditworksonlywhenthemotorstartsanditwillbreakupafterthecurrentgoesregularly.ThiseffectcanbereachedbyconnectingthePTCThermistorinseriesinstartingassistantloopandcuttingofftheassistantloopwhenPTCRentersthestateofhighresistance.
Advantages
ThestartingcircuitwithPTCownsthefeatureofbeingeconomic,reliable,simplewhichisbetterthantheheavyhammerstartingcircuitAdditionally,Ithasthecharacteristicsofbeingcontactless,lowernoise,highreliability,longserviceandsoon.