Thanks to explanations of Takashi Memorandum [1] I have an FME workspace that calls another using this transformer.
[1] http://fme-memorandum-takashi.blogspot.com.es/2013/09/workspacerunner-examples.html
So, this works perfect:

But, If I use main.fme instead of main.fmw the process fails.
Thanks, A.