Abstract:
It is an object of this invention to provide a dynamo-electric machine rotor which effectively and uniformly cools a rotor coil outside a rotor core by forming a ventilating groove in the rotor coil, tolerates large field current, and has high reliability. There is provided a dynamo-electric machine rotor in which spaced core slots are formed in a cylindrical rotor core  30 , rotor coils  10  of stacked turns are fitted into the core slots to form multiple nested rings around a magnetic pole of the rotor, ends of the rotor coils are fixed by an retaining ring, and a spacer  20  is arranged in each of circumferential gaps between the ends of the rotor coils, wherein each spacer  20  has a length not more than the lengths of linear portions  12  at the ends of corresponding ones of the rotor coils  10 , a cut-out  22  for ventilation of coolant gas is formed across at least one of two sides of the spacer, and the spacer is in contact with the rotor coils at the two sides of the spacer at a position located furthest inside in the radial direction of the rotor and an arbitrary position.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a dynamo-electric machine rotor and, more particularly, to a rotor coil cooling structure configured to feed coolant gas between adjacent coil ends.  
         [0003]     2. Related Art  
         [0004]     A dynamo-electric machine such as a turbine generator is composed of a hollow cylindrical stator and a cylindrical rotor with a diameter somewhat smaller than that of the hollow portion which are concentrically arranged with an air gap between them. In each of the stator and rotor, conductive bars, i.e., so-called coils of copper or the like are arranged in the axial direction of core slots. When the rotor is rotated while its coils are energized, current is induced on the stator side.  
         [0005]     At this time, since high heat is generated in the stator and rotor due to an electrical loss or the like, special cooling is required. The stator and rotor are forcedly cooled by feeding coolant gas into the machine by means of, e.g., placement of a fan in the rotor. In particular, the cooling performance of rotor coils which use rotational centrifugal force as the driving force for coolant gas is an important factor which influences the performance and build of a generator.  
         [0006]      FIG. 29  shows a sectional view of ends of conventional rotor coils.  FIG. 30  shows a horizontally spread-out view of the ends of the rotor coils. As shown in  FIGS. 29 and 30 , a conventional dynamo-electric machine rotor has a ventilating groove  10 A in the longitudinal direction of each of rotor coils  10  and cools the rotor coils  10  by feeding coolant gas A through the grooves.  
         [0007]     The rotor coils  10  of stacked turns are fitted into slots which are circumferentially formed at predetermined intervals in a core  30  integrated with a rotor shaft  13  to form multiple nested rings. Ends  10 E of the rotor coils  10  which are located outside an end of the rotor core are held by an retaining ring  34  and an retaining ring support  35  against rotational centrifugal force. As shown in  FIG. 29 , the ends  10 E of the rotor coils  10 , whose outer side is surrounded by the retaining ring  34 , are held at predetermined intervals while a spacer  20  shown in  FIG. 31  is arranged between each two adjacent coils. An insulating cylinder  40  is inserted to maintain electrical insulation between the outermost portion of the rotor coil ends  10 E and the retaining ring  34 .  
         [0008]     Since field current for energization flows through the rotor coils  10 , electric heat is generated, and the temperatures of the coils rise. In addition to the insulating cylinder  40 , insulators (not shown) are inserted between adjacent stacked turns of each rotor coil and between the core slots and the rotor coils, and the upper temperature limit is defined on the basis of the heat-proof temperatures of the insulators and the like.  
         [0009]     As described above, coolant gas passes through an air gap between the rotor shaft  13  and the retaining ring support  35  and is guided to the retaining ring  34 , and part thereof is guided to a ventilating channel in each rotor coil  10  from a ventilating inlet formed in a side of the rotor coil  10 . The coolant gas guided into the ventilating channel of the rotor coil  10  flows through the ventilating channel in the longitudinal direction of the rotor coil  10 , thereby cooling the rotor coil  10 . After that, the coolant gas passes through a radial duct  14  in the core and is discharged to the outer periphery of the rotor.  
         [0010]     In addition to this, a method is disclosed in National Publication of International Patent Application No. 2000-508508 or the like in which no ventilating groove is formed in a coil itself, a ventilating groove is formed in each side of a spacer arranged between coils, and partition plates are provided all around the inner periphery of rotor coils, thereby enhancing cooling between coils. As shown in  FIG. 32 , each partition plate has an opening near the border between a coil linear portion  12  and a coil circular portion  11 , and cooling is performed by causing coolant gas to pass in the directions indicated by arrows.  
         [0011]     However, in the cooling method, in which each rotor coil has the ventilating groove  10 A, coolant gas flows in the longitudinal direction. Accordingly, the temperature of the coolant gas becomes higher toward the downstream side, and the temperature of one of the coils which is circumferentially distant from a magnetic pole center and is near the core end is higher than that of one near the magnetic pole center where an inlet  10 B for coolant gas is located, as shown in  FIG. 30 . Also, the more distant from the center one of the rotor coils is, the longer the rotor coil is. Accordingly, the temperature of an outer coil is higher than that of an inner coil, and it is highly possible that the distribution of temperature becomes wider in the axial direction and circumferential direction of the rotor coils.  FIG. 33  shows an example of a set of temperature distributions.  
         [0012]     The temperatures of rotor coils are strictly limited by the upper temperature limit for a member used as an insulator for the coils. If the temperature is locally high at a part of a coil, there arises the need to limit field current and suppress the amount of heat generated even when the temperatures at other parts are sufficiently lower than the upper temperature limit. Accordingly, it is impossible to turn up a dynamo-electric machine. Also, if temperatures differ among coils of a large number of turns, shaft vibration occurs due to imbalance in thermal expansion among the rotor coils, and the reliability of the generator decreases.  
         [0013]     On the other hand, in a method in which a ventilating groove is formed in each side of a spacer arranged between coils, and partition plates are provided below rotor coils outside a rotor core, thereby performing cooling between the coils, as in National Publication of International Patent Application No. 2000-508508, the flow rate of coolant gas passing through a ventilating groove in a spacer is lower than that of coolant as passing through a ventilating groove in a coil, and thus the cooling performance is lower. Also, the method requires components for the partition plates and man-hours for assembling them, thus leading to cost increase.  
         [0014]     A rotor coil of a turbine generator is formed by stacking a plurality of turns each generally having a thickness of about several mm. Since the thin turns are not tightly bound nor held by one another, they each thermally stretch with an increase in temperature during the operation of the generator. For this reason, it is desirable for a spacer to be in contact with all turns at longitudinally identical positions, if possible.  
         [0015]     However, in the invention described in National Publication of International Patent Application No. 2000-508508, a zigzag ventilating groove is formed in each side of a spacer. Accordingly, surfaces on a side of each spacer which are in contact with a coil are staggered and are discontinuous in the longitudinal direction. For this reason, the coil end holding power in the technique described in National Publication of International Patent Application No. 2000-508508 is lower than a rotor which uses a plain spacer without a ventilating groove in each side.  
       SUMMARY OF THE INVENTION  
       [0016]     The present invention has been made in consideration of the above-described conventional drawbacks, and has as its object to provide a dynamo-electric machine rotor which can sufficiently cool a rotor coil with simple configuration without providing a component such as a partition plate and whose coil holding power is not impaired at an end of the rotor coil.  
         [0017]     In order to achieve the object, according to the present invention, there are provided  
         [0018]     a dynamo-electric machine rotor in which spaced core slots are formed in a cylindrical rotor core, rotor coils of stacked turns are fitted into the core slots to form multiple nested rings around a magnetic pole of the rotor and, ends of the rotor coils are fixed by an retaining ring, and a spacer is arranged in each of circumferential gaps between the ends of the rotor coils,  
         [0019]     wherein each spacer has a length not more than lengths of linear portions at the ends of corresponding ones of the rotor coils, a cut-out is formed across at least one of two sides of the spacer which are in contact with the linear portions at the ends of the corresponding rotor coils except for a portion located inward in a radial direction of the rotor and an arbitrary portion to form a coolant gas ventilating channel having an axial extremity which communicates with a through hole formed in a tooth of the rotor core, and the spacer is in contact with the rotor coils at the portion located inward in the radial direction of the rotor and the arbitrary portion serving as remaining portions and  
         [0020]     a dynamo-electric machine rotor in which spaced core slots are formed in a cylindrical rotor core, rotor coils of stacked turns are fitted into the core slots to form multiple nested rings around a magnetic pole of the rotor, ends of the rotor coils are fixed by an retaining ring, and a spacer is arranged in each of circumferential gaps between the ends of the rotor coils,  
         [0021]     wherein each spacer has a length not more than lengths of linear portions at the ends of corresponding ones of the rotor coils, a cut-out is formed across at least one of two sides of the spacer which are in contact with the linear portions at the ends of the corresponding rotor coils except for a portion located inward in a radial direction of the rotor and an arbitrary portion to form a coolant gas ventilating channel having an axial extremity which bends toward space formed below the rotor coils, and the spacer is in contact with the rotor coils at the portion located inward in the radial direction of the rotor and the arbitrary portion serving as remaining portions, and  
         [0022]     a subslot which communicates with the space formed below the rotor coils is formed in the rotor core.  
         [0023]     In the present invention, a cut-out is formed across a side of a spacer inserted between conductors of ends of rotor coils except for a portion located inward in a radial direction of a rotor and an arbitrary portion to facilitate ventilation of coolant gas. This makes it possible to effectively cool a rotor coil with simple configuration and provide a dynamo-electric machine rotor whose coil holding power is not impaired at an end of the rotor. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is a plan view showing the locations of rotor coils and spacers outside a rotor core of a dynamo-electric machine according to a first embodiment of the present invention;  
         [0025]     FIGS.  2 (A) to  2 (D) show a spacer for a rotor coil of the dynamo-electric machine according to the first embodiment of the present invention,  FIG. 2 (A) being a side view,  FIG. 2 (B) being a plan view,  FIG. 2 (C) being a cross-sectional view,  FIG. 2 (D) being an end view;  
         [0026]      FIG. 3  is a sectional view of a spacer for a rotor coil according to a first application of the first embodiment of the present invention;  
         [0027]     FIGS.  4 (A) to  4 (C) show a spacer for a rotor coil according to a second application of the first embodiment of the present invention,  FIG. 4 (A) being a left side view,  FIG. 4 (B) being a right side view,  FIG. 4 (C) being a cross-sectional view;  
         [0028]      FIG. 5  is a view showing a section of the rotor coils and spacer placed according to the first embodiment of the present invention;  
         [0029]      FIG. 6  is a view showing coolant gas through holes at an end of the rotor core according to the first embodiment of the present invention;  
         [0030]     FIGS.  7 (A) and  7 (B) show a spacer for a rotor coil according to a third application of the first embodiment of the present invention,  FIG. 7 (A) being a side view,  FIG. 7 (B) being a cross-sectional view;  
         [0031]      FIG. 8  is a side view of a spacer for a rotor coil according to a fourth application of the first embodiment of the present invention;  
         [0032]      FIG. 9  is a side view of a spacer for a rotor coil according to a fifth application of the first embodiment of the present invention;  
         [0033]      FIG. 10  is a side view of a spacer for a rotor coil according to a sixth application of the first embodiment of the present invention;  
         [0034]      FIG. 11  is a side view of a spacer for a rotor coil according to a seventh application of the first embodiment of the present invention;  
         [0035]      FIG. 12  is a side view of a spacer for a rotor coil according to an eighth application of the first embodiment of the present invention;  
         [0036]      FIG. 13  is a side view of a spacer for a rotor coil according to a ninth application of the first embodiment of the present invention;  
         [0037]      FIG. 14  is a plan view showing the locations of rotor coils and spacers outside a rotor core of a dynamo-electric machine according to a second embodiment of the present invention;  
         [0038]     FIGS.  15 (A) to  15 (C) show a spacer for a rotor coil according to the second embodiment,  FIG. 15 (A) being a side view,  FIG. 15 (B) being a plan view,  FIG. 15 (C) being a cross-sectional view;  
         [0039]      FIG. 16  is a cross-sectional view of a spacer for a rotor coil according to a first application of the second embodiment of the present invention;  
         [0040]     FIGS.  17 (A) to  17 (D) show a spacer for a rotor coil according to a second application of the second embodiment of the present invention,  FIG. 17 (A) being a plan view,  FIG. 17 (B) being a cross-sectional view,  FIG. 17 (C) being a front view,  FIG. 17 (D) being a rear view;  
         [0041]      FIG. 18  is a sectional view showing a state in which the spacer is placed between the rotor coils according to the second embodiment of the present invention;  
         [0042]      FIG. 19  is a side view of a spacer for a rotor coil according to a third application of the second embodiment of the present invention;  
         [0043]      FIG. 20  is a side view of a spacer for a rotor coil according to a fourth application of the second embodiment of the present invention;  
         [0044]      FIG. 21  is a side view of a spacer for a rotor coil according to a fifth application of the second embodiment of the present invention;  
         [0045]      FIG. 22  is a side view of a spacer for a rotor coil according to a sixth application of the second embodiment of the present invention;  
         [0046]      FIG. 23  is a side view of a spacer for a rotor coil according to a seventh application of the second embodiment of the present invention;  
         [0047]      FIG. 24  is a side view of a spacer for a rotor coil according to an eighth application of the second embodiment of the present invention;  
         [0048]      FIG. 25  is a side view of a spacer for a rotor coil according to a ninth application of the second embodiment of the present invention;  
         [0049]      FIG. 26  is a side view showing the flow of cooling air in the spacer according to the second embodiment of the present invention;  
         [0050]      FIG. 27  is a graph showing a flow ratio versus pressure drop characteristic which serves as a basis for cooling action by the flow of the cooling air in  FIG. 26 ;  
         [0051]      FIG. 28  is a graph showing temperature distributions in the longitudinal direction of the rotor coil when the present invention is applied;  
         [0052]      FIG. 29  is an axial sectional view showing the configuration of a conventional dynamo-electric machine rotor;  
         [0053]      FIG. 30  is a horizontally spread-out view of a conventional rotor coil;  
         [0054]      FIG. 31  is a perspective view showing a spacer for the conventional rotor coil;  
         [0055]      FIG. 32  is a perspective view showing a conventional rotor coil; and  
         [0056]      FIG. 33  is a graph showing temperature distributions in the longitudinal direction of the conventional rotor coil. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0057]     Embodiments of the present invention will be explained below with reference to the drawings.  
       First Embodiment  
     Configuration  
       [0058]     A first embodiment of the present invention will be explained with reference to FIGS.  1  to  13 .  FIG. 1  is a spread-out view of rotor coils  10  when an retaining ring and an insulating cylinder at an end of a rotor of a generator are removed, as seen from above. At ends  10 E of the rotor coils  10 , space is provided between coil conductors of each adjacent two of coil circular portions  11  which are located outside a rotor core  30 , and an integral-type spacer  20  whose details are shown in FIGS.  2 (A) to  2 (D) is provided between each adjacent two of coil linear portions  12 .  
         [0059]     As will be described in detail later, each spacer  20  has two sides which serve as coil contacting portions. A plurality of cut-outs are longitudinally formed in each coil connecting portion, and a communicating hole is formed in each of remaining parts. The spacer  20  is configured to feed coolant gas through a ventilating channel which is composed of the cut-outs and communicating holes and feed the gas after cooling to through holes  31  formed in a tooth of the core. Note that two of the through holes  31  are vertically formed in a tooth  33  of the rotor core  30 , as shown in  FIG. 6 .  
         [0060]     FIGS.  2 (A) to  2 (D) are views showing an example of a spacer.  FIG. 2 (A) is a perspective view,  FIG. 2 (B) is a side view,  FIG. 2 (C) is a top view, and  FIG. 2 (D) is an end view of  FIG. 2 (B) taken along line IV-IV, as seen from an outlet for coolant gas. The spacer  20  in this example has a plurality of cut-outs  22  longitudinally formed at predetermined intervals in each of surfaces which are in contact with one sides of the linear portions  12  of the corresponding rotor coils  10  shown in  FIG. 1 , i.e., each of two contacting portions  21 . A communicating hole  23  is formed in a remaining portion sandwiched between each adjacent two of the cut-outs  22 . The spacer  20  is configured to feed coolant gas through the cut-outs  22  and communicating holes  23 , as indicated by arrows. The linear portions  12  at ends of the rotor coils  10  directly exchange heat with coolant gas in the cut-outs  22  and are cooled. In the case of the spacer  20  in FIGS.  2 (A) to  2 (D), parts  21   h  which are each sandwiched between the corresponding cut-outs  22  and a portion  21   a  located inward in the radial direction of the rotor which is at a lower portion of a side of the spacer  20  serve as remaining portions and constitute the contacting portion  21 , as in  FIG. 2 (A), and hold a side of the linear portion  12  at the end  10 E of the corresponding rotor coil  10 .  
         [0061]     Note that the shape of the spacer  20  is not limited to that shown in FIGS.  2 (A) to  2 (D) and that the spacer  20  may be formed to have the shape shown in  FIG. 3  or  4 .  FIG. 3  shows a spacer  20 A which has the cut-outs  22  only in one side, the left side in  FIG. 3 . FIGS.  4 (A) to  4 (C) show a spacer  20 B whose contacting portions  21  on the right and left sides are asymmetrical. Note that FIGS.  4 (A),  4 (B), and  4 (C) are a front view, a rear view, and a right side view, respectively, of the spacer  20 B.  
         [0062]      FIG. 5  shows a radial sectional view of the spacer  20  in FIGS.  2 (A) to  2 (D) placed between the linear portions  12  at ends of the corresponding rotor coils  10 , taken at the cut-outs  22 . A ventilating channel  26  which is independent of lower space formed between the linear portions  12  at ends of the corresponding rotor coils  10  and a rotor shaft is formed at a side of the corresponding rotor coil  10  by the spacer  20 .  
         [0063]      FIG. 6  is a cross-sectional view of the rotor core  30 , with which an end face of each spacer  20  is in contact. The through holes  31  for discharging coolant gas, which communicate with the ventilating channels  26  of the spacer  20  and communicate with an air gap between the rotor and a stator, are formed in each tooth  33  between slots  32  containing the rotor coils  10 .  
         [0064]     The shape of each spacer need not be limited to one having one ventilating channel  26  on each side, as in the spacers  20 ,  20 A, and  20 B described above. Each spacer  20  may be formed such that the radially inward contacting portion  21   a  and a portion  21   b  near the center in the heightwise direction of the spacer  20  serve as a contacting portion which is in contact with a side of the corresponding rotor coil  10 , thereby forming two horizontally split ventilating channels  26 U and  26 D at the side of the linear portion  12  of the rotor coil  10 , as in, e.g., FIGS.  7 (A) and  7 (B) and  8 .  
         [0065]     FIGS.  7 (A) and  7 (B) show a spacer  20 C in which the cut-out  22  is split into upper and lower portions by the linear contacting portion  21   b  provided near the center in the heightwise direction.  FIG. 8  shows a spacer  20 D in which the contacting portion  21   b  is wavy. The flow directions of coolant gas are indicated by two rows A and B of arrows passing through the two ventilating channels  26 U and  26 D, which extend in the longitudinal direction of each of the spacers  20 C and  20 D.  
         [0066]      FIG. 9  shows an example of a spacer  20 E in which the contacting portion  21   b  is doglegged downward, i.e., toward the rotor shaft at a fourth to third of the length of the spacer  20 E from an inlet for coolant gas.  
         [0067]     In the spacer  20 E shown in  FIG. 9 , the contacting portion  21   b , which horizontally splits the ventilating channel  26  into the ventilating channels  26 U and  26 D, is linear. In the case of a spacer  20 F shown in  FIG. 10 , the contacting portion  21   b  is wavy.  
         [0068]      FIGS. 11 and 12  each show an example in which the radially inward contacting portion  21   a  and the contacting portion  21   b , which diagonally extends downward, are further extended inward beyond the radially inward contacting portion  21   a  of an extremity on the coil circular portion  11  side, as in contacting portions  21   c  and  21   d , to project to be further inside than the inner periphery of the coils  10 . In this case, the contacting portion  21   b , which horizontally splits the ventilating channel  26  into the ventilating channels  26 U and  26 D, may be linear, as in a spacer  20 G in  FIG. 11  or may be wavy, as in a spacer  20 H in  FIG. 12 .  
         [0069]      FIG. 13  shows a configuration in which the ventilating channel  26  at a side of the linear portion  12  of the corresponding rotor coil  10  is configured to meander, as indicated by the arrows A, by forming a rotor radially outward side contacting portions  21   e  and the radially inward contacting portion  21   a  of a spacer  20 I to alternately project toward the ventilating channel  26 .  
       Operation  
       [0070]     Each of the spacers  20 ,  20 A, . . . ,  20 I, which are placed between the coil linear portions  12 , is in contact with the coils  10  at its two sides at the radially inward contacting portions  21   a , has cut-outs formed across the sides except for the radially inward contacting portions  21   a , and is integrated with the coils  10  using a clip or the like. This configuration makes it possible to ensure the ventilating channel  26 , which is separate from a channel formed between the linear portions  12  at ends of the coils  10  and the rotor shaft, at a side of the linear portion  12  of the coil  10 . Since each spacer is of integral type, the cross-sectional area between the coils  10  decreases, and the flow rate of coolant gas flowing between the coils  10  can be increased. Also, formation of the through holes  31  in the teeth  33  between the slots of the rotor core  30  makes it possible to ensure outlets for coolant gas flowing between the linear portions  12  of the rotor coils  10 .  
         [0071]     It is possible to horizontally split the ventilating channel  26  at a side of each coil  10  by bringing the spacer  20  into contact with the coil  10  not only at the radially inward contacting portion  21   a  of the spacer  20  but also at the contacting portion  21   b  near the center in the heightwise direction of the spacer  20 . Also, bending of the contacting portion  21   b  downward at about a fourth to third of the length of the spacer  20  from an extremity on the coil circular portion  11  side makes it possible to provide an inlet for coolant gas in the bottom surface of the spacer  20 .  
         [0072]     Additionally, the radially outward side contact surfaces  21   e  and radially inward contact surface  21   a  of each spacer  20  formed to alternately project toward the ventilating channel  26  makes it possible to enhance the holding power of the spacer  20 .  
       Effect  
       [0073]     As described above, according to the first embodiment, the ventilating channel  26 , which is separate from a channel below the coils  10 , is provided at a side of each coil  10  using any of the spacers  20  to  20 I. Since coolant gas guided to the radially outward side by rotational centrifugal force is taken in and does not return to the channel below the coils  10 , coolant gas can be effectively used to cool the sides of the coils  10 . This makes it possible to achieve temperature distributions as shown in  FIG. 28  better than those of a conventional rotor shown in  FIG. 33 . Also, it is possible to perform uniform cooling by changing the positions of the contacting portions  21  of each spacer  20 .  
         [0074]     Provision of the through holes  31  for discharging coolant gas flowing between the coils  10  toward the air gap in the teeth  33  of the rotor core  30  makes it possible to discharge coolant gas whose temperature is increased after cooling between the coils  10  toward the air gap without letting the coolant gas flow into the rotor. The configuration is advantageous to a large rotating machine which requires minimization of the temperature of gas flowing into the rotor.  
         [0075]     Horizontal splitting of the ventilating channel  26  at a side of the coil  10  into two makes it possible to reduce imbalance, i.e., restrain much of coolant gas from flowing to the radially outward side due to centrifugal force and perform uniform cooling. By forming the coil contacting portion  21   b  of the spacer  20  for splitting the ventilating channel  26  into two to be wavy, it is possible to axially change a turn position where the coil is not cooled and expect uniform cooling.  
         [0076]     Placement of an inlet for coolant gas in the bottom surface of each spacer  20  makes it possible to make more use of the effects of rotational centrifugal force and increases the opening area. Accordingly, a pressure drop at the inlet can be reduced. Extension of the contacting portions  21   a  and  21   b , which are to come into contact with the coil  10 , to below the coil, as in the contacting portions  21   c  and  21   d , is expected to increase the uptake of gas. The radially outward side contacting portions  21   e  and the radially inward contacting portion  21   a  of each spacer  20  formed to alternately project toward the ventilating channel  26  make it possible to increase the area of contact with the coil  10 . A large-capacity machine whose coils  10  have high heat stretchability can ensure cooling power and holding power.  
       Second Embodiment  
     Configuration  
       [0077]     A second embodiment of the present invention will be explained with reference to FIGS.  14  to  27 .  FIG. 14  shows a spread-out view of rotor coils  10  at an end of a rotor of a generator, as seen from above. An integral-type spacer  203  shown in FIGS.  15 (A) to  15 (C) is provided between coil linear portions  12  at ends of each adjacent two of the rotor coils  10 , which are located outside a rotor core  30 . As shown in  FIG. 15 (A), the spacer  20 J has a contacting portion  21   f  which bends coolant gas A to the radially inward of the rotor near an outlet and discharges the coolant gas A. After the coolant gas A is discharged to between the corresponding coils  10  and a rotor shaft, it flows into a subslot  32   a  which is formed below a core slot portion  32 . Note that the spacer  20 J may be placed between coil circular portions  11 . The spacer  20 J in FIGS.  15 (A) to  15 (C) has cut-outs in each of surfaces which are in contact with one side of the linear portions  12  at an end of the corresponding rotor coils  10 . However, each spacer may have a cut-out only in one side, as in a spacer  20 K shown in  FIG. 16 , or may have cut-outs such that contacting portions  21  on the right and left sides which are in contact with the corresponding coils  10  are asymmetrical, as in a spacer  20 L shown in FIGS.  17 (A) to  17 (D). Basically, each spacer only needs to be structured to come into contact with the corresponding coil linear portions  12  at its radially inward contacting portions. Note that  FIG. 17 (A) is a plan view,  FIG. 17 (B) is a cross-sectional view,  FIG. 17 (C) is a front view, and  FIG. 17 (D) is a rear view.  
         [0078]      FIG. 18  shows a radial sectional view of the spacer  20 J in FIGS.  15 (A) to  15 (C) placed between the linear portions  12  at ends of the corresponding rotor coils  10 . A ventilating channel  26  which is independent of lower space formed between the corresponding coils  10  and the rotor shaft is formed at a side of the corresponding coil  10  by the spacer  20 J.  
         [0079]     An outlet  25  is formed in the ventilating channel  26  immediately in front of an end of the rotor core  30  by removing a part of a coil contacting portion  21   a  on the radially inward side of the spacer  20 J. The spacer  20 J is configured to discharge coolant gas to space located further inside than the inner periphery of ends of the corresponding coils  10  which is formed between the coils  10  and the rotor shaft.  
         [0080]     Note that each spacer  20  may be formed such that the radially inward contacting portion  21   a  and a contacting portion  21   b  near the center in the heightwise direction of the spacer  20  are in contact with the coil  10  to split the ventilating channel  26  at a side of the corresponding coil  10 . The ventilating channel  26  may be split such that the contacting portion  21   b  in contact with the corresponding coil  10  is linear, as in a spacer  20 M in  FIG. 19 , or such that it is wavy, as in a spacer  20 N in  FIG. 20 , and coolant gas may be discharged from the outlet  25 .  
         [0081]     As shown in  FIG. 21 , a spacer  20 O may be formed such that about a fourth to third of the spacer  20 O from an extremity on the coil circular portion  11  side is not in contact with the linear portion  12  of the corresponding coil  10  at the bottom surface of the spacer  20 O and such that a part of the contacting portion  21   b  horizontally splitting the ventilating channel  26  formed at a side of an end  10 E of the coil  10  which is in the fourth to third may be diagonally extended downward to the radially inward side of the extremity on the coil circular portion  11  side of the spacer  20 O. At this time, the contacting portion  21   b , which horizontally splits the ventilating channel  26 , may be linear, as shown in  FIG. 21 , or may be wavy, as in a spacer  20 P shown in  FIG. 22 .  
         [0082]     As in a spacer  20 Q shown in  FIG. 23 , the contacting portions  21   a  and  21   b , which diagonally extend downward, may be further extended inward beyond the radially inward contacting portion  21   a  of an extremity on the coil circular portion  11  side, as in contacting portions  21   c  and  21   d , to project to below the corresponding coil  10 . At this time, the contacting portion  21   b , which splits the ventilating channel  26 , may be linear, as in the spacer  20 Q shown in  FIG. 23 , or may be wavy, as in a spacer  20 R shown in  FIG. 24 . As in a spacer  20 S shown in  FIGS. 25 , radially outward contacting portions  21   e  which are to come into contact with an insulating cylinder in  FIG. 27  and the radially inward contacting portion  21   a  on the core  30  side may be provided to alternately project toward the ventilating channel  26 , and a channel at a side of each coil  10  may be configured to meander.  
         [0083]      FIG. 26  shows a sectional view of the end of the rotor, which uses the spacer  20 Q.  FIG. 27  is a graph showing the relationship between gas discharged from the spacers  20 J to  20 S and coolant gas (main stream).  
         [0084]     As shown in  FIG. 26 , a stream of coolant gas flowing from the left side of  FIG. 26  along the rotor shaft passes by an retaining ring support  35  provided at the left end (with respect to  FIG. 26 ) of an retaining ring  34  and is split into a main stream C which travels straight ahead to the right (with respect to  FIG. 26 ) along the rotor shaft, streams A and B which pass through ventilating channels  26 U and  26 D provided in the spacer  20 Q, and a stream which heads upward (with respect to  FIG. 26 ) away from the rotor shaft.  
         [0085]     When the streams A and B having passed through the ventilating channels  26 U and  26 D provided in the spacer  20 Q reach the core end, they meet the main stream C having flown along the rotor shaft and flow into the subslot  33  formed to axially extend through the core. After the streams cool the rotor core, they are discharged from an air gap.  
         [0086]     A drop as shown in  FIG. 27  occurs at the meeting of the two streams. More specifically, assuming that the main stream C is a stream along the rotor shaft and that the tributaries A and B are streams flowing through the spacer, a pressure drop with respect to a flow ratio is plotted with the abscissa representing the flow ratio between the tributaries and the main stream and the ordinate representing a pressure drop. As shown in  FIG. 27 , the drop is negative when the flow ratio is small and turns positive and increases as the flow ratio increases. That is, the characteristic shown in  FIG. 27  has a positive slope.  
         [0087]     The cooling effect of the coils is enhanced by using the drawing action of the main stream (the coolant gas stream C along the rotor shaft) on the tributaries (the coolant gas streams A and B passing through the spacer) in a region where the flow ratio is small.  
       Operation  
       [0088]     Each of the spacers  20 J to  20 S, which are placed between the coil linear portions  12  at ends of the rotor coils  10 , is in contact with the coil linear portions  12  at its two sides at radially inward side contact surfaces, has cut-outs formed across the sides except for the radially inward side contact surfaces, and is integrated with the coils  10  using a clip or the like. This configuration makes it possible to ensure the ventilating channel  26 , which is separate from a channel formed between the coil linear portions  12  and the shaft, at one side or two sides of the coil linear portion  12 . Also, since each spacer is of integral type, the cross-sectional area between the coils  10  decreases, and the flow rate of coolant gas flowing between the coil linear portions  12  can be increased. Additionally, it is possible to ensure outlets for coolant gas flowing between the coil linear portions  12  by forming each of the spacers  20 J to  20 L such that coolant gas is discharged to space below the coil linear portions  12  immediately in front of the end of the rotor core  30 .  
         [0089]     Provision of not only the radially inward contacting portion  21   a  but also the contacting portion  21   b , which is in contact with the coil  10  near the center in the heightwise direction of a spacer  20 , as in the spacers  20 M to  20 R, makes it possible to horizontally split the ventilating channel  26  into two at a side of the coil  10 . Also, bending of the contacting portion  21   b  downward at about a fourth to third of the length of each of the spacers  200  to  20 R from an extremity on the coil circular portion  11  side makes it possible to provide an inlet for coolant gas inlet in the bottom surface of the spacer  20 .  
         [0090]     Additionally, the radially outward contacting portions  21   e  and radially inward contacting portion  21   a  formed to alternately project toward the ventilating channel  26 , as in the spacer  20 S, makes it possible to enhance the holding power of the spacer  20 .  
       Effect  
       [0091]     As described above, according to the second embodiment, a ventilating channel which is separate from a channel formed between the coil linear portions  12  and the shaft is provided at a side of the coil linear portion  12  at an end of each rotor coil  10  using any of the spacers  20 J to  20 S. With this configuration, coolant gas guided to the radially outward side by rotational centrifugal force is taken in, and the coolant gas can be effectively used to cool the side of the coil linear portion  12  while the coolant gas is passing by the side of the coil linear portion  12 . This makes it possible to achieve temperature distributions better than those of a conventional rotor as shown in  FIG. 28 .  
         [0092]     It is possible to perform uniform cooling by axially changing the positions of the contacting portions  21  of each of the spacers  20 J to  20 S. The shape of each of the spacers  20 J to  20 S makes it possible to return coolant gas to a channel formed between an end of the coil  10  and the rotor shaft immediately in front of the rotor core  30  and feed the coolant gas through the subslot  33 . Accordingly, the configuration is advantageous to a small rotating machine in, e.g., that it eliminates the need to form the through hole  31  in the tooth  33  of the core  30  and can reduce the cost.  
         [0093]     Horizontal splitting of the ventilating channel  26  at a side of the coil linear portion  12  into two makes it possible to reduce imbalance, i.e., restrain much of coolant gas from flowing to the radially outward side due to centrifugal force and perform uniform cooling. By forming the coil contacting portion  21   b  of the spacer  20  for splitting the ventilating channel  26  into two to be wavy, it is possible to further axially change a turn position where the coil is not cooled and expect uniform cooling.  
         [0094]     Placement of an inlet for coolant gas of each of the spacers  20 O to  20 S between an end of the coil  10  and the rotor shaft makes it possible to make more use of the effects of rotational centrifugal force and increases the opening area. Accordingly, a pressure drop at the inlet can be reduced. Extension of the contacting portions  21 , which are to come into contact with the linear portion  12  at an end of the coil  10 , to below the coil, as in the contacting portions  21   c  and  21   d , is expected to increase the uptake of gas. The radially outward side contact surfaces and radially inward side contact surface of the spacer  20 S formed to alternately project toward the ventilating channel  26  make it possible to increase the area of contact with the linear portion  12  at an end of the coil  10 . A large-capacity machine whose coils have high heat stretchability can ensure cooling power and holding power.