P$16\mathrm{.}38.$ A $60-$Hz $480-$V$-$rms $200-$hp delta$-$connected synchronous motor runs under no$-$load conditions. The field current is adjusted for minimum line current, which turns out to be $16\mathrm{.}45$ A rms$.$ The per$-$phase armature impedance is $\backslash (\backslash$mathrm$\{$Rs$\}+\backslash$mathrm$\{$j$\}$ X $\backslash$mathrm$\{$~s$\}=0\mathrm{.}05+\backslash$mathrm$\{$j$\}1\mathrm{.}4\backslash ).($Until now in this chapter, we have neglected Rs$.$ However, it is significant in efficiency calculations.$)$ Estimate the efficiency of the machine under full$-$load conditions operating with $90$ percent leading power factor.