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Reliability of Thermal Relays in Automotive Applications
KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
2017 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Despite the vast increase of relays in automotive applications, little is known of how to perform reliability tests on them. Reliability of relays is defined as the probability of a relay to function without failure, when operated correctly, for a given period of time, under stated conditions.Accordingly, there is a need for improving life-expectancy test methods for relays. The immediate objective of this research project is to develop a guideline of how to check reliability of relays.Identifying the main parameters that affect reliability, perform an endurance test and material analyses of the tested relays were the main areas of interest in this work. In addition, common failure modes during the relays performance were identified.The results show that supplied voltage, breaking current and load type are parameters that affect arc duration and, thus, the contact damage. Most common failure modes were contact welding and increase in contact resistance due to arc erosion and oxide formation. Moreover, contact resistance stability has been proved to be a factor capable to determine the quality of contacts and to predict early failures in relays.

Abstract [sv]

Trots den omfattande ökningen av reläer i biltillämpningar så är lite känt om hur man utför pålitliga tester på dem. Reläers pålitlighet kan definieras som sannolikheten för ett relä att fungera utan fel när den opereras korrekt under en given tidsperiod och under angivna villkor.Följaktligen så finns ett behov av att förbättra testmetoder för den förväntade livslängden hos reläer. Det huvudsakliga ändamålet med detta examarbete är att utveckla riktlinjer för hur man undersöker pålitligheten hos reläer.Arbetet har utförts vid Scania CV AB i Södertälje och de huvudsakliga intresseområdena var att identifiera de viktigaste parametrar som påverkar pålitligheten hos reläer samt att utföra uthållighetstest och materialanalys på de reläer som provades.Resultaten visar att matningsspänningen, brytströmmens magnitud sant lasttype är parameterar som påverkar ljusbågens brinntid och, därigenom, kontaktskador. De mest förekommande felmoderna är kontaktsvetsning och ökning av kontaktresistansen på grund av ljusbågserosion och oxidformation. Resultaten visade vidare att kontaktresistansens stabilitet är en faktor som indikerar kontaktkvaliten och kan användas för att prediktera tidiga felfall i reläerna.

Place, publisher, year, edition, pages
2017. , p. 109
Series
TRITA-EE, ISSN 1653-5146 ; 2017:012
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-202965OAI: oai:DiVA.org:kth-202965DiVA, id: diva2:1079865
External cooperation
SCANIA
Educational program
Master of Science in Engineering - Electrical Engineering
Available from: 2017-03-09 Created: 2017-03-09 Last updated: 2017-03-09Bibliographically approved

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