FEMM - Transformer design and frequency
I can not understand why the transformer at 0 Hz operates similarly
  with the transformer at 50 Hz


More than likely this is because the primary inductance is too small for a proper 50 Hz transformer and therefore the current flowing is limited by circuit resistance.

On the other hand, if you are "powering" the primary by setting a current, then the same magnitude of current will flow as in the DC case and both will have the same amount of magnetic flux generated.

You need to state what you are doing for any further help I think.