Answer Posted / guest
u know every metal oxidises by giving its valence
electron.so metal corrode with time.metal corrodes due to
environmental effects like moisture etc.suppose u r giving
+48 then metal will loose its electron quickly & will be
oxidised. So the metal will be corroded quckly & u have to
replace it .But if u give -48 then metal will not loose its
electrons because the metal wire will be negatively
charged.if metal somehow looses its electron then metal can
draw electron from the current becoz the wire is negatively
charged.so metal will not corrode with time.Thats why we
uses -ve supply(-48v).Moreover if we use +ve supply(more
load more corrosion)ie if load is high metal will be corrode
Quickly.in our MSC sites we use load upto 600 amps.in this
case if we will use +ve supply we have to replace the wires
frequently.if we use -ve supply there will be no problem
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