A star-connected $3$-phase, $400\; V$, $50$ $\text{ kVA}$, $50\; Hz$ synchronous motor has a synchronous reactance of $1$ $\text{ohm}$ per phase with negligible armature resistance. The shaft load on the motor is $10$ $\text{kW}$ while the power factor is $0.8$ leading. The loss in the motor is $2\:kW$. The magnitude of the per phase excitation emf of the motor, in volts, is ______________. (round off to nearest integer).