The Hispano didn't use an electrically-powered belt feed - it was recoil-powered.
The gun recoiled about 25mm per shot. This movement was used to wind up a coil spring in that drum-shaped feed unit. The coil spring pulled the belt through the BFM (Belt Feed Mechanism). This arrangement meant that the pull on the belt was smooth instead of being a series of jerks.
You can tell which Hispanos were fed from the 60-round drum magazine and which were belt fed by looking at the muzzle. The drum-fed guns had a long slotted muzzle brake to reduce the recoil. The belt fed guns had this taken off because the recoil was needed to drive the belt feed.
Tony Williams: Military gun and ammunition website: http://www.quarry.nildram.co.uk