$5HP,400V,50Hz,10A,4P$ della connected three phase induction motor is to be operated by $\frac{E}{f}$ method $(E=$ self induced emf of armature, $1=$ supply frequency$)$ with scaling factor $K=0,2.$

The machine parameters per phase are $R_1=0\mathrm{.}5{}_1{R}_2^{\text{'}}=0\mathrm{.}6,x_1=>x_2^{\text{'}}=1\mathrm{.}2.$ For the stator current drawn to be $7\mathrm{.}5$ A $,$ calculate the input supply voltage and frequency if it is practically controlled by V$/$f $N=$ Supply voltage of armature$)$ approach.