Dear Jeeva,
In case of populating the losses part for any switch, there is a particular type of file format supported:
1) The file must be in .xml format(which is available as you mentioned).
2) The .xml file needs to be only lookup table type.
Usually, there will be three types of .xml available which are table or lookup type, formula type and both lookup and formula type. You can easily differentiate it by mentioned format name in the xml file itself as show below(pointed by red arrow)-

However, even if this type of format is available, you can manually populate the fields by following steps in this link.
Hope this helps!
Best Regards.