you won't have a converter, but you have an INVERTER, which creates heat when inverting 12v to 120v power to your fridge, and outlets. As this heat 'heats up' and reaches a certain temperature internally, a separate installed fan comes on to remove the heat from your storage bay where the inverter is located, which is what you are hearing.
Sometimes these fans run for a while, and sometimes it seems they never turn off - some of us will touch it's 'sensor' with a piece of ice to trick it into cutting off.
Otherwise, it's just a little fan, like in your computer, and not a big draw or big deal, though it can seem a little annoying if it's right below where you are sleeping, etc.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada.... formerly Georgia, then NorthCarolina, now Alabama : )