[sagargv]

@big-G , the surge current idea which u think is responsible is acceptable .. but a few questions :

1. if the psu in bullzi's pc took 700W power , then the load on the ups is about 1100 kVA which i doubt is something beyond a apc 1000 kVA to handle for a few milliseconds.

2. If the psu didnt get enough power , could you explain why it blew up instead of shutting off .

3. Could you explain why this of "inrush" of current just after the ups switches occur only in PFC capable psu's ? why not in other psu's too ? Why is it more pronounced in PFC capable psu's ?

I agree , ur explanation seems quite logical but i can accept it only if i understand the answers to the above questions.