fedora updation
 

I am trying to update my fedora13 to fedora15 using commands

yum update rpm
yum -y update
yum preupgrade
preupgrade

but this process is taking too much of time

Is there any other process to update my fedora with less time

Yes there is: make a backup of your home folder, get and burn the FC15 and re-install...should take less time than the method you use - a method not really favored by Fedora's makers.