Memory error in thermal simulation

Hello,

I am simulating a three phase power transformer of 220KVA and when I want to do the thermal simulation of it. It appears me a memory error but I dont understand why this happens because I had done a correct electromagnetic simulation before and I dont think the mesh is very heavy. Maybe there is something wrong defined in the thermal simulation. I put here my model if you can prove it and see if you have the same problem and how I can fix it. 

To do this thermal simulation I have removed the infinite box. After that I have defined the power losses in the volume region and the thermal exchanges with the environment as face region in all the faces of the model. 

Thank you,

Iñigo