Simulation of OCC, for a 3 phase Alternator using MATLAB/Simulink
The toolbox Matlab offer to simulate power system with Simulink is 
Simscape Power Systems.  This toolbox is more oriented toward simulating a power network than the transformer itself. Infortunaly, Matlab doesn't come with out of the box solution for that problem. 

Solidworks seem to offer a suit to simulate electromagnetic system with one of their toolbox . 

The main problem with Solidwork is that it costs a lot of money. So the most pragmatic solution would be simulate with Matlab code or FEMM, or depending on the scale of the project either go with an already made solution or if you just want to get the transformer characteristic, do the experimentation in real life.