Air cooling means for dynamoelectric machine

Claim 1

A dynamoelectric machine having a wound stator, a frame that encloses the stator and comprises front and rear end members, said frame being substantially imperforate except for axially opening apertures in said end members that provide for circulation of cooling air into and out of the interior of the frame, a rotor having a shaft journaled in bearings in said end members, a cooling fan constrained to rotate with said shaft and located forwardly adjacent to the front end members, and a fan enclosure comprising an apertured front wall forwardly adjacent to the fan and a substantially imperforate circumferential side wall extending rearwardly from said front wall in concentric surrounding relation to the fan, said side wall having a rear portion which is larger in diameter than the frame and which is disposed radially opposite a front portion of the frame all around the same, said machine being characterized by: air barrier means extending radially across the space between said rear portion of the side wall and said front portion of the frame and circumferentially around at least most of the frame, said air barrier means cooperating with the frame and with the side wall of said fan enclosure to define an annular plenum chamber in the radially outer portion of said fan enclosure from which pressurized air is mainly constrained to flow into the interior of the frame, and thus through the entire length thereof, by way of said apertures in the end members, while no more than a minor portion of air from said plenum chamber is directed across the exterior of the frame, said air barrier means comprising an arcuate strip, curved to closely embrace said front portion of the frame and having a radial thickness to extend substantially entirely across the space between said side wall and said front portion of the frame, said strip being secured in said space by fastening means that also secure the fan enclosure to the frame.