電機啟動型熱敏電阻器 馬達啟動用正溫度系數(shù)熱敏電阻器，只要用于電冰箱、空調馬達啟動、空調變頻機啟動、馬達過熱保護等。 工作原理：馬達啟動器是利用PTC陶瓷的電流－時間特性，當電壓施加于PTCR時，開始有大電流I流過，經(jīng)過一定時間ts后，隨著PTCR溫度的升高，電阻值迅速增大，導致電流也急劇下降，這段時間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、負載電阻及工作電壓，當外電壓撤銷時，PTCR將冷卻至常溫電阻值。利用這個原理，在家用電冰箱和空調機等電器馬達啟動上得到了廣泛的使用。應該說明，當使用PTCR的延遲性能時，如果要重復同一延遲時間，應間隔一定時間tr（即所謂的恢復時間），使PTCR恢復到原始狀態(tài)溫度，所以應避免立即重復動作，否則PTCR不能提供持續(xù)的大電流，使壓縮機無法正常啟動工作，會導致壓縮機燒毀。 電機在啟動時，要克服本身的慣性，同時還要克服負載的反作用力（如冰箱壓縮機啟動時必須克服制冷劑的反作用力），因此電機啟動時需要較大的電流和轉矩。當轉動正常后，為了節(jié)約能源，需要的轉矩又要大幅度下降。給電機加一組輔助線圈，只在啟動時工作，正常后它就斷開。將PTC熱敏電阻串聯(lián)在啟動輔助線圈，啟動后PTC熱敏電阻進入高阻態(tài)切斷輔助線圈，正好可以達到這種效果. 產(chǎn)品優(yōu)勢：采用帶有PTCR的啟動電路具有經(jīng)濟、可靠、電路簡單等特點，優(yōu)于過去的重錘式啟動電路，它具有無觸點、低噪聲、高可靠、長壽命等特點。 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.