This is a plugin originally authored by Steve Smith. It detects all ways to access your original WordPress feeds and redirects them to your FeedBurner
Normally, the format should be like the link below:
It uses the tag_slug parameter to define which tag should it be.
There is a native method provided by WordPress which allows you to get the category feed link easily. The only thing you need to input is the category id.
get_category_feed_link( $category->term_id )