Gas cooled alternating current machine

A gas cooled alternating current machines having a motor mounted on a shaft and surrounded by a stator, said rotor and said stator each having opposed ends, said stator having a stator central part including a laminated sheet metal pack and two stator end parts, a fan attached to said shaft at each rotor end and a shell mounted in association with the fan for conveying a cooling medium towards said stator and said rotor, the stator sheet metal pack being clamped between two end plates and subdivided by radially extending cooling ducts into individual partial packs, the stator sheet metal pack being surrounded by a casing having walls defining plural corners, comprising:

• plural upper and lower ducts for the removal of the cooling gas formed in respective of the casing corners, said ducts bounded only by the walls of the casing and surfaces of the sheet metal pack separated by the sheet metal pack and extending over the total length of the sheet metal pack;
• the stator end parts formed both as cooling gas inlet and cooling gas outlet casings, said stator end parts having a height corresponding approximately to that of the stator central part and widths protruding on both sides relative to the stator central part, each inlet and outlet casing including a separating wall which in conjunction with said shell substantially subdivides the respective inlet and outlet casing into four chambers, including a cooling gas induction chamber, a winding head chamber and a pair of cooling gas outlet flow chambers which are located symmetrically about a vertical plane;
• each cooling gas outlet flow chamber having at least one outlet flow opening and each being connected to a respective lower duct and a respective upper duct of the stator central part via openings in the end plates of the stator central part;
• said separating walls in each stator end part between the winding head chamber and the cooling gas outlet flow chambers being located in pairs symmetrically about the vertical plane and separating the winding head chamber and the cooling gas outlet flow chambers from one another;
• and
• said separating walls having by-pass openings through which cooling gas is led in a first cooling branch through the rotor and stator and in a second cooling branch in parallel to the first cooling branch through the stator winding head;
• said separating walls in the stator end parts extending in an axial direction from the end plates to the shell allocated to the fans;
• said separating walls defining a cross-section which at most coincides approximately with the external contour of the stator metal sheet and at least lies outside a hypothetical cylinder obtained by a circle inscribed on the sheet metal pack external contour;
• and
• said separating walls contacting a respective internal side of the lower and upper casing wall of the stator end parts and including by-pass openings approximately evenly distributed over the periphery thereof.