In my opinion, in p.u.: Tmax=1.3*VLL^2/xd" for phase-to-phase short-circuit at generator terminals that means 1.3*1^2/.16=8.125 and Tmax=VLL^2/xd”=6.25 for 3 phase short-circuit.
In order to find this in Nm you have to multiply by Trated=Prated/(2*pi()*rpm/60)
Trated=1300*1000/(2*pi()*1500/60)= 8276.057 Nm