Max Flux Density for DC Generator Cores

[DUET]

Hello!
I would like to know what is the maximum flux density that can be used in a core for DC generator without taking the core in it's saturation point now a days?

 

[UltrafastPED]

You'll need to do a search - magnetic saturation of materials is tabulated:
http://en.wikipedia.org/wiki/Saturation_(magnetic )