?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F300%2F&rft.title=Arc+Phenomena+in+low-voltage+current+limiting+circuit+breakers&rft.creator=Thompson%2C+Alice+B.&rft.creator=Richardson%2C+G.&rft.creator=Dellar%2C+Paul&rft.creator=McGuinness%2C+M.&rft.creator=Budd%2C+Chris&rft.subject=Energy+and+utilities&rft.subject=Materials&rft.description=Circuit+breakers+are+an+important+safety+feature+in+most+electrical+circuits%2C+and+they+act+to+prevent+excessive+currents+caused+by+short+circuits%2C+for+example.+Low-voltage+current+limiting+circuit+breakers+are+activated+by+a+trip+solenoid+when+a+critical+current+is+exceeded.+The+solenoid+moves+two+contacts+apart+to+break+the+circuit.+However%2C+as+soon+as+the+contacts+are+separated+an+electric+arc+forms+between+them%2C+ionising+the+air+in+the+gap%2C+increasing+the+electrical+conductivity+of+air+to+that+of+the+hot+plasma+that+forms%2C+and+current+continues+to+flow.+The+currents+involved+may+be+as+large+as+80%2C000+amperes.%0D%0A%0D%0ACritical+to+the+success+of+the+circuit+breaker+is+that+it+is+designed+to+cause+the+arc+to+move+away+from+the+contacts%2C+into+a+widening+wedge-shaped+region.+This+lengthens+the+arc%2C+and+then+moves+it+onto+a+series+of+separator+plates+called+an+arc+divider+or+splitter.%0D%0A%0D%0AThe+arc+divider+raises+the+voltage+required+to+sustain+the+arcs+across+it%2C+above+the+voltage+that+is+provided+across+the+breaker%2C+so+that+the+circuit+is+broken+and+the+arcing+dies+away.+This+entire+process+occurs+in+milliseconds%2C+and+is+usually+associated+with+a+sound+like+an+explosion+and+a+bright+ash+from+the+arc.+Parts+of+the+contacts+and+the+arc+divider+may+melt+and%2For+vapourise.%0D%0A%0D%0AThe+question+to+be+addressed+by+the+Study+Group+was+to+mathematically+model+the+arc+motion+and+extinction%2C+with+the+overall+aim+of+an+improved+understanding+that+would+help+the+design+of+a+better+circuit+breaker.%0D%0A%0D%0AFurther+discussion+indicated+that+two+key+mechanisms+are+believed+to+contribute+to+the+movement+of+the+arc+away+from+the+contacts%2C+one+being+self-magnetism+(where+the+magnetic+field+associated+with+the+arc+and+surrounding+circuitry+acts+to+push+it+towards+the+arc%0D%0Adivider)%2C+and+the+other+being+air+flow+(where+expansion+of+air+combined+with+the+design+of+the+chamber+enclosing+the+arc+causes+gas+flow+towards+the+arc+divider).%0D%0A%0D%0AFurther+discussion+also+indicated+that+a+key+aspect+of+circuit+breaker+design+was+that+it+is+desirable+to+have+as+fast+a+quenching+of+the+arc+as+possible%2C+that+is%2C+the+faster+the+circuit+breaker+can+act+to+stop+current+flow%2C+the+better.+The+relative+importance+of+magnetic+and+air+pressure+effects+on+quenching+speed+is+of+central+interest+to+circuit+design.&rft.date=2010&rft.type=Study+Group+Report&rft.type=NonPeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F300%2F1%2Farc.pdf&rft.identifier=++Thompson%2C+Alice+B.+and+Richardson%2C+G.+and+Dellar%2C+Paul+and+McGuinness%2C+M.+and+Budd%2C+Chris++(2010)+Arc+Phenomena+in+low-voltage+current+limiting+circuit+breakers.++%5BStudy+Group+Report%5D+++++