Question $2$

a$)$ Separately excited D$.$C$.$ generator has armature circuit resistance of $\backslash (0\mathrm{.}1\backslash$Omega $\backslash )$ and total brush$-$drop is $2$ V $.$ When running at $1200$ rpm $,$ it delivers a current of $100$ A at $250$ V to a load of constant resistance. If the generator speed drop to $800$ rpm $,$ with fieldcurrent unaltered, determine

i$)$ the current delivered to load

$(8$ marks$)$

ii$)$ new load resistance when current $100$ A at $700$ rpm

$(4$ marks$)$

b$)$ A short$-$shunt compound generator has armature, shunt field and series field resistances of $\backslash (0\mathrm{.}5\backslash$Omega$,100\backslash$Omega $\backslash ),$ and $\backslash (0\mathrm{.}3\backslash$Omega $\backslash )$ respectively. When supplying a load of $8$ kW at a terminal voltage of $250$ V the input power supplied by the driving motor is $10\mathrm{.}4$ kW $.$ Calculate the

i$)$ generated emf

$(6$ marks$)$

ii$)$ efficiency

iii$)$ friction and windage losses

iv$)$ total fixed losses.

$[$Total: $\backslash (\backslash$mathbf$\{25\}\backslash )$ marks$]$