Answer:
a. 30.O7A
b. no reading
Explanation:
for the first load with power factor 0.8, we calculate the reactive power
note the reactive power is calculated as
[tex]Q=Ptan(cos^{-1}\alpha )\\[/tex]
where p=power
a. for the first load the reactive power is
[tex]Q=10tan(cos^{-1} 0.8)\\Q=7.5kvar\\[/tex]
for the second load the reactive power is
[tex]Q=-15tan(cos^{-1} 0.9)\\Q=-7.265kvar[/tex]
The total reactive power is the summation of both reactive power in he load
[tex]Q_{total}=7.5+(-7.265)\\Q=-0.235kvar[/tex]
and the total real power is 25kw
Hence using Pythagoras theorem to calculate the apparent power we have
[tex]S=\sqrt{P^{2}+Q^{2}}\\ S=25.001KVA[/tex]
Hence we can determine the source current using
[tex]S=\sqrt{3}VI\\ I=\frac{25.001*10^{3}}{\sqrt{3} *480} \\I=30.07A[/tex]
b. in a balance 3phase system, there is no neutral current, Hence the ammeter will read zero current
