Dynamoelectric machine rotor ventilation

#The present invention relates to dynamoelectric machines having a rotor that is cooled using forced convection of gases to remove heat from the rotor. It is particularly applicable to high speed machines where the windage loss experienced by the machines is significant.

#This invention is an improvement on my Canadian Patent 1,238,933 issued Jul. 5, 1988 and entitled Cooling System with Reduced Windage Loss. My Canadian Patent discloses a sealed rotor dynamoelectric machine having reduced windage loss by having turning vanes at opposite ends of the rotor. One set of vanes is utilized for directing gas into the rotor and another set of vanes for directing the gas from the rotor into adjacent rotary structure for circulation. The rotor has cooling slots defined by the interpolar space between two adjacent poles of the rotor and a shield or cover member placed across the slot to enclose the interpolar space. Any gas directed by the vanes into the slot moves axially along the slot and is prevented by the shield cover from moving radially out the slot, across the air gap and into the stator member surrounding the rotor. As a result, the use of the vanes and the cover shield provide a reduction in windage loss associated with gas flow for cooling the rotor structure

#Accordingly there is a need to provide a ventilation system for a dynamoelectric machine wherein windage loss associated with coolant gases entering the rotor interpolar spaces or ducts present a minimal windage loss while at the same time having the advantage associated with the use of interpolar space coolant ducts.

#For a better understanding of the nature and objects of the present invention reference may be had to the accompanying diagrammatic drawings in which:

#FIG. 1 is a radial cross-section of a dynamoelectric machine according to the present invention; and,

#FIG. 2 is a partial axial cross-section of the rotor and stator of the dynamoelectric machine of the present invention.

#Referring to FIG. 1 there is shown a cross-sectional view of a portion of a vertically mounted dynamoelectric machine 10 having a rotor 11 and a stator 12. While the dynamoelectric machine 10 is shown with a vertical shaft 15, such as is normally used in a hydro generator, the present invention may also be used with horizontal shaft machines. Between the rotor 11 and the stator 12 is an air gap 14 which separates these two structures. The rotor 11 is attached to a rotatable shaft 15 which is mounted in a bearing structure (not shown) to permit rotation of the shaft 15 with rotor 11. A hub member 16 is keyed or otherwise suitably secured to shaft 15. Radially extending support plate 17 extends from the hub member 16 to rotor core structure 18. Laminations 22 which comprise the rotor core carry poles 28 which have axially extending ventilating ducts or cooling ducts 23. Adjacent poles 28, are shown in FIG. 2 with the ventilation duct 23 extending along the interpolar space between the poles 28. In FIG. 2, a shield 25 covers the interpolar space 23 and thereby prevents gas flow from extending radial outward of the ventilation duct 23 and directs the gas flow axially through the ventilation ducts 23 as shown in FIG. 1.

#The rotor 11 is mounted for rotation circumferencially within the stator 12. The stator 12 is shown to have regularly extending ventilation passages 37. Conductors extend through the stator core 36 and the end turns 38 of the conductors are schematically represented. A housing 40 extends from the stator 12 forming a chamber 41. A cooler 42 is mounted to the housing 40 so the coolant gas or gas which is passed through the passages 37 will pick up heat generated from the stator core 36, pass into chamber 41, and have heat removed as gas passes through the cooler 42. A wall 43 extends around the stator defining chamber 44. Motor driven fans 45 and 46 are mounded in openings in respective walls 47 and 48 to move the coolant gas from the chamber 44 into the chambers 50 and 51 where the coolant gas passes over the entrance 38 and into the air gap 14.

#It will be seen that there is a circulation of a coolant gas or gas to cool the stator 12 and another to cool the rotor 11. The rotor 11 is provided with a first shroud member 60 mounted to the rotor 11 adjacent a first axial end of the rotor 62 for rotation therewith. The first shroud 60 extends radially over and is spaced from the radially extending first end 62 of the rotor to define a radial gas inlet path 64. The first shroud 60 has a first radial inner end 66 adjacent to and spaced from the shaft 15 to define a gas inlet 68. The first shroud 62 further has a second radial outer end 70 mounted to the rotor 11 adjacent to and spaced apart from the ventilation ducts 23 so as to communicate the gas from the radial gas inlet path 64 into and through the ventilation ducts 23 of the rotor 11. A plurality of radially extending blades 65 are mounted to the rotor support plate 17 across from the shroud end 70. Blade 65 assists in the angular acceleration of the gas flow.