the machine has a stator (19) in a pot-shaped housing (10), a claw pole rotor system on a driven shaft with two pole rings (21) and a fan arrangement generating a cooling air flow which carries hot air to a liquid medium enclosing the housing. The fan arrangement has somewhat radial blades (29) on the flat end of each pole ring extending close to a hub (12) holding the shaft bearing (13). Somewhat radial ribs (32) on the base of an annular chamber (31) have straight or curved intermediate grooves at the height of the fan blades
