Úvod
Thermalfuseismainlyusedforoverloadprotection.Ifthefuseisproperlyplacedinthecircuit,thefusewillfuseandcutoffthecurrentwhenthecurrentrisestoacertainheightandheatabnormally,whichprotectsthesafeoperationofthecircuit.
Whenacircuitbreaksdownorisabnormal,thecurrentwillcontinuetorise,andtherisingcurrentmaydamagesomeimportantcomponentsinthecircuit,oritmayburnthecircuitorevencauseafire.Ifthefuseiscorrectlyinstalledinthecircuit,thefusewillfuseandcutoffthecurrentwhenthecurrentabnormallyrisestoacertainheightandheat,therebyprotectingthesafeoperationofthecircuit.
Pracovní princip
Whencurrentflowsthroughtheconductor,theconductorwillgenerateheatduetotheresistanceoftheconductor.Andthecalorificvaluefollowsthisformula:Q=0.24I2RT;whereQisthecalorificvalue,0.24isaconstant,Iisthecurrentflowingthroughtheconductor,Ristheresistanceoftheconductor,andTisthecurrentThetimeflowingthroughtheconductor;accordingtothisformula,itisnotdifficulttoseethesimpleworkingprincipleofthefuse.
Whenthematerialandshapeofthefusearedetermined,itsresistanceRisrelativelydetermined(ifthetemperaturecoefficientofresistanceisnotconsidered).Whencurrentflowsthroughit,itwillheatup,anditsheatwillincreasewiththeincreaseoftime.Thecurrentandresistancedeterminethespeedofheatgeneration.Thestructureofthefuseanditsinstallationstatusdeterminethespeedofheatdissipation.Iftherateofheatgenerationislessthantherateofheatdissipation,thefusewillnotblow.Iftherateofheatgenerationisequaltotherateofheatdissipation,itwillnotfuseforalongtime.Iftherateofheatgenerationisgreaterthantherateofheatdissipation,thenmoreandmoreheatwillbegenerated.Andbecauseithasacertainspecificheatandquality,theincreaseinheatismanifestedintheincreaseintemperature.Whenthetemperaturerisesabovethemeltingpointofthefuse,thefuseblows.
Specifikace produktu
1) Řada RH (typ slitiny s nízkým bodem tání, tvar plastové skořepiny, jmenovitá provozní teplota 70℃-150℃, 1/2/3/5 Arovaný proud);
2) RF série (typ slitiny s nízkým bodem tání, keramický válcový tvar, jmenovitá provozní teplota 70℃-240℃, 1/2/3/5/10/15/20/25 Arovaný proud);
3) RSsérie (typ slitiny s nízkou teplotou tání, keramický/plastový tvar montážního otvoru, jmenovitá provozní teplota 70℃-280℃, 5/10 Arovaný proud);
4) RY série (organický chemický typ, kovový válcový tvar, jmenovitá provozní teplota 65 ℃-300 ℃, 10/15/16/20 Arovaný proud).
Vysvětlení pojmů
Ratedoperatingtemperature(Tf):
Thetemperaturefuseistestedaccordingtothestandardmethodtochangeitsconductivestatetemperature.AccordingtothesafetystandardsbasedonIEC6091,thethermalfusemustoperatewithintherangeofratedoperatingtemperature+0/-10°C(thetolerancerangespecifiedbytheJapaneseElectricalAppliancesManagementLawis±7°C).
Measuredoperatingtemperature:
Thetemperaturefuseisheatedinthesiliconeoilbathatarateof0.5-1°Cperminute,measuredundertheconditionthatthedetectioncurrentislessthan10mAFusingtemperature.Itistheactualoperatingtemperatureofthethermalfuse.
Holdingtemperature(Th):
Whenthethermalfusepassestheratedcurrent,itcanmaintainthehighesttemperaturefor168hourswithoutchangingitsconductivestate.
Limittemperature(Tm):
Themaximumtemperatureatwhichthethermalfusecanwithstand10minuteswithoutreconnection.
Ratedcurrent(Ir):
Maximální proud, který může nést malá pojistka.
Ratedvoltage(Ur):
Maximální provozní napětí špatné pojistky.