Patent Publication Number: US-2023134826-A1

Title: Cooling manifold for rotary electric machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. patent application Ser. No. 16/745,419, filed on Jan. 17, 2020. The contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates generally to rotary electric machines, and specifically to a cooling manifold for rotary electric machines. 
     BACKGROUND 
     All electric motors and generators, i.e., rotary electric machines, generate heat during operation. The heat can be removed using a fluid such as air or a liquid. In some examples, the cooling structure is provided in the slot to provide more direct contact with the winding coils and thereby more effectively remove heat generated therefrom. A manifold can be used to coordinate the flow of the cooling liquid to, from, and between the slots. 
     SUMMARY 
     In one example, a rotary electric machine includes a stator extending along an axis and having teeth arranged about the axis. The teeth are circumferentially spaced apart by slots. Conductors extend around the teeth and through the slots. The conductors are electrically connected to one another to form phases. Cooling devices are provided in the slots. Each cooling device is fluidly connected to an inlet tube for supplying cooling fluid to the cooling device and an outlet tube for removing cooling fluid from the cooling device. A manifold includes a first cooling channel fluidly connected to each inlet tube and a second cooling channel fluidly connected to each outlet tube such that all the cooling devices in the machine are fluidly connected in parallel. 
     In another example, a rotary electric machine includes a stator extending along an axis and having teeth arranged about the axis. The teeth are circumferentially spaced apart by slots. Conductors extend around the teeth and through the slots. The conductors are electrically connected to one another to form phases. Cooling devices are provided in the slots. Each cooling device is fluidly connected to an inlet tube for supplying cooling fluid to the cooling device and an outlet tube for removing cooling fluid from the cooling device. A manifold includes a first cooling channel fluidly connected to each inlet tube and a second cooling channel fluidly connected to each outlet tube. For each cooling device the cooling fluid flows a first circumferential distance within the first cooling channel to the inlet tube and flows a second circumferential distance within the second cooling channel away from the outlet tube. The sum of the first and second circumferential distances is substantially equal for each cooling device. 
     In another example, a rotary electric machine includes a stator extending along an axis and having teeth arranged about the axis. The teeth are circumferentially spaced apart by slots. Conductors extend around the teeth and through the slots. The conductors are electrically connected to one another to form phases. Cooling devices are provided in the slots. Each cooling device is fluidly connected to an inlet tube for supplying cooling fluid to the cooling device and an outlet tube for removing cooling fluid from the cooling device. A manifold includes a first cooling channel fluidly connected to each inlet tube and a second cooling channel fluidly connected to each outlet tube. At least one motor connection is electrically connected to the conductors and secured to the manifold outside the first and second cooling channels. The at least one motor connection is aligned with the first and second cooling channels such that heat generated in the at least one motor connection is removed by the cooling fluid flowing through the first and second cooling channels. 
     In another example, a manifold for a rotary electric machine having a stator extending along an axis and includes teeth arranged about the axis. The teeth are circumferentially spaced apart by slots. Conductors extend around the teeth and through the slots. A cooling device is provided in each slot and has an inlet tube and outlet tube associated therewith. The manifold includes a first cooling channel fluidly connected to the inlet tubes of the cooling devices and a second cooling channel fluidly connected to the outlet tubes of the cooling devices such that all the cooling devices in the machine are fluidly connected in parallel. 
     In another example, a rotary electric machine includes a stator forming a housing extending along an axis and having teeth arranged about the axis. The teeth are circumferentially spaced apart by slots. Conductors extend around the teeth and through the slots. The conductors are electrically connected to one another to form phases. A rotor is rotatable within and relative to the stator. A fan includes a shaft secured to and rotatable with the rotor for generating airflow to cool the rotor. 
     Other objects and advantages and a fuller understanding of the invention will be had from the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a front view of a rotary electric machine having an example cooling manifold. 
         FIG.  2    is a section view of the rotary electric machine taken along lines  2 - 2  of  FIG.  1   . 
         FIG.  3 A  is a front view of a cooling device for the rotary electric machine. 
         FIG.  3 B  is an exploded view of a portion of the cooling device of  FIG.  3 A . 
         FIG.  3 C  is a section view of the cooling device taken along lines  3 C- 3 C of  FIG.  3 A- 3 A . 
         FIG.  3 D  is a section view of the cooling device taken along lines  3 D- 3 D of  FIG.  3 B- 3 B . 
         FIG.  4    is a top view of a portion of the cooling device. 
         FIG.  5    is a top view of a manifold and motor connections of the rotary electric machine. 
         FIG.  6 A  is a top view of the manifold of  FIG.  5    with the motor connections and cover plates. 
         FIG.  6 B  is a section view of the manifold of  FIG.  6 A  taken along line  6 B- 6 B. 
         FIG.  6 C  is a section view of the manifold of  FIG.  6 B  taken along line  6 C- 6 C. 
         FIG.  6 D  is an enlarged view of portion of  FIG.  6 C  in which the cooling devices are fluidly connected in series. 
         FIG.  7 A  is a section view of a rotor of the rotary electric machine. 
         FIG.  7 B  is a front view of a fan rotatable with the rotor of  FIG.  7 A . 
         FIG.  8    is a section view of the rotor of  FIG.  7 A  within a stator. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates generally to rotary electric machines, and specifically to a cooling manifold for rotary electric machines. Referring to  FIGS.  1 - 2   , one example rotary electric machine  20  includes a stator  22  extending about and along an axis  24  and forming a housing. The stator  22  includes a ring-shaped core  28  formed from stacked laminations formed from an electrically conductive material. 
     Teeth  30  extend radially inward from the core  28  towards the axis  24 . The teeth  30  are arranged circumferentially about the axis  24  and extend substantially the entire axial length of the stator  22 . The teeth  30  can be releasably connected to the core  28  with tooth retention devices  34  or integrally formed therewith (not shown). As shown, each tooth retention device  34  extends into a slot  36  in one of the teeth  30  and a slot  38  in the core  28 . Regardless, the teeth  30  are circumferentially spaced apart from one another by slots  32 . 
     Winding coils or coils  40  formed from one or more conductors, e.g., electrically conductive material such as copper, are wound around the teeth  30  and pass through the slots  32 . In one example, the winding coils  40  are wound in a 3-phase configuration such that a portion of the winding coils are in phase A, a portion of the winding coils are in phase B, and a portion of the winding coils are in phase C. Each phase A-C receives the same or substantially the same amount of current. Other phase configurations are contemplated. Multiple winding coils  40  can be electrically connected in series or in parallel and still receive the same amount of current. In a 3-phase configuration, phases can be connected in either a wye or delta configuration. 
     In the 3-phase configuration, the current can flow from a junction box (not shown) to motor connections  280  electrically connected to the winding coils  40 . The current flows from the connections  280 , through the winding coils  40 , and to motor connections  290 . In one example, the motor connections  280  are bus bar connections and the motor connections  290  are star point connections. Regardless, the motor connections  280 ,  290  are axially aligned with the stator  22  and positioned outside the slots  32 . 
     The winding coils  40  can be wound onto the stator  22  in any number of known manners, e.g., concentrated wound, distributed wound or hairpin wound. As shown, the winding coils  40  are formed from rectangular wire bent into a diamond shape and distributed wound around the teeth  30 . The winding coils  40  are oriented in the slot  32  such that in cross-section the length (the longer dimension) extends radially towards the axis  24 . The width (the smaller dimension) extends generally circumferentially about the axis  24 . Multiple winding coils  40  in the same slot  32  are arranged abutting or adjacent one another in the radial direction and abutting or adjacent the associated tooth  30 . 
     A circumferential space or gap  42  can be formed in the slot  32  between adjacent pairs of winding coils  40 . A cooling device  70  is provided within each gap  42  for cooling the winding coils  40  during operation of the rotary electric machine  20 . A liner  71  formed from electrically insulating material, e.g., an aramid polymer, is provided in the gap  42  and is wrapped around the cooling device  70 . Consequently, the liner  71  is provided circumferentially between the winding coils  40  in the same slot  32  and circumferentially between the cooling device  70  and each winding  40 . The liner  71  can extend substantially the entire axial and radial lengths of the slot  32 . Alternatively, the liner  71  can be omitted (not shown) such that the cooling device  70  abuts multiple winding coils  40  in the slot  32 . 
     Referring to  FIGS.  3 A- 3 B , the cooling device  70  includes first and second tubes  72 ,  92  for providing a bi-directional flow path for cooling fluid within each slot  32 . As shown, the first tube  72  is on outer tube and the second tube  92  is an inner tube. A conductive tab  77  formed from stacked laminations is secured along the length of the first tube  72 . The tab  77  can be secured to the first tube  72  via brazing, soldering, etc. To this end, the tab  77  can be secured to the first tube  72  in the manner shown and described in U.S. application Ser. No. 15/394,522, the entirety of which is incorporated by reference herein. The tubes  72 ,  92  and tab  77  can be formed from conductive materials, such as aluminum and copper-based materials. The tubes  72 ,  92 , and tab  77  can be formed from the same material or different materials. 
     As further shown in  FIG.  3 C , the first tube  72  extends along a centerline  73  from a first end  74  to a second end  76 . A passage  78  extends the entire length of the first tube  72 . A hollow projection  80  is provided at the first end  74  and extends along the centerline  73 . A countersink  82  extends from the second end  76  towards the first end  74  and is coaxial with the centerline  73 . 
     The second tube  92  extends along a centerline  93  from a first end  94  to a second end  96 . A passage  98  extends the entire length of the second tube  92 . The second tube  92  is positioned within the passage  78  of the first tube  72 . As shown, the centerlines  73 ,  93  of the first and second tubes  72 ,  92  are offset from one another. 
     The first and second tubes  72 ,  92  can be secured to one another. In one example, one or more projections  84  (see  FIG.  4   ) are provided along the length of the first tube  72  and extend radially towards the centerline  73 . The projections  84  engage the second tube  92  to pin or secure the second tube in place within the first tube  72 . The projections  84  can be formed by crimping the first tube  72  inward into the passage  78  while the second tube  92  is disposed therein. Alternatively, the first tube  72  can be drawn, e.g., cold drawn, through a die to include the projections  84 . In any case, the projections  84  prevent or limit relative axial and rotational movement between the tubes  72 ,  92 . 
     Alternatively or additionally, the first and second tubes  72 ,  92  can be secured to one another with a metallurgical bond, which can be accomplished by, for example, a brazed connection, a welded connection, a solid state welded connection or a soldered connection. The connection can extend the entire length of the second tube  92  or along portions of the length of the second tube. In another example, the first and second tubes  72 ,  92  are not secured to one another (not shown). 
     Regardless, the second tube  92  is positioned within the first tube  72  such that the first end  94  of the second tube extends axially beyond the first end  74  of the first tube ( FIG.  3 B ). The lengths of the first and second tubes  72 ,  92  are configured such that this positions the second end  96  of the second tube  92  offset from the second end  76  of the first tube. More specifically, the second end  96  of the second tube  92  is longitudinally recessed or spaced from the countersink  82  to form a longitudinal space or gap  100  therebetween. Accordingly, the tubes  72 ,  92  can have the same axial length and be axially shifted or offset from one another to achieve the gap  100 . 
     An end cap  110  is secured to the first ends  74 ,  94  of the first and second tubes  72 ,  92 . The end cap  110  extends from a first end  112  to a second end  114 . As shown, the end cap  110  is substantially L-shaped. The end cap  110  includes a first passage  116  and a second passage  118  each extending the length of the end cap. The first passage  116  is fluidly connected to the passage  98  in the second tube  92 . The second passage  118  is fluidly connected to the passage  78  in the first tube  72 . 
     A hollow projection  113  is provided on the first end  112  of the end cap  110  and is aligned with the second passage  118 . A countersink  119  is provided in the second end  114  of the end cap  110  for slidably receiving the projection  80  on the first end  74  of the first tube  72 . The second end  114  of the end cap  110  also includes a recess  117  for slidably receiving the first end  94  of the second tube  92 . The positioning and depths of the recess  117  and countersink  119  in the second end  114  of the end cap  110  longitudinally offset the first ends  74 ,  94  from one another, thereby offsetting the second ends  76 ,  96  from one another. 
     A coupling  120  (see also  FIG.  3 D ) is secured to the first end  112  of the end cap  110 . The coupling  120  extends from a first end  122  to a second end  124 . First and second passages  126 ,  128  extend the length of the coupling  120 . The passages  126 ,  128  include respective countersinks  125 ,  127  at the first end  122 . A first recess  129  extends into the second end  124  and is in fluid communication with the second passage  128 . A second recess  131  extends from the first recess  129  to the first passage  126  for fluidly connecting the same. The first recess  129  slidably receives the first end  112  of the end cap  110 . The second recess  131  slidably receives the projection  113  on the first end  112 . Consequently, the first passage  126  is fluidly connected to the first passage  116  in the end cap  110 . The second passage  128  is fluidly connected to the second passage  118  in the end cap  110 . 
     The interfaces between the first and second tubes  72 ,  92 , the end cap  110 , and the coupling  120  can be fluidly sealed in several ways. For example, the interfaces can be brazed, soldered, welded (such as solid state welding) or crimped together. In each case, the interfaces are securely held together in a fluid-tight manner. 
     A pair of tubes  130 ,  140  extends into the first and second passages  126 ,  128 , respectively, in the first end  122  of the coupling  120 . The tubes  130 ,  140  are fluidly connected to a reservoir  150  (see  FIG.  3 A ) holding cooling fluid. The cooling fluid can be, for example, water, ethylene glycol or mixtures thereof. 
     An end cap  160  ( FIGS.  3 A and  3 C ) is received in the countersink  82  in the second end  76  of the first tube  72  for closing the second end without sealing or closing the second end  96  of the second tube  92 . In other words, the end cap  160  does not eliminate the gap  100 . This forms a closed path for the flow of cooling fluid through the cooling device  70 . A projection  162  on the end cap  160  receives the tab  77  of laminations. 
     The cooling device  70  is oriented in the slot  32  such that the end cap  110  extends from the tubes  72 ,  92  radially outward and away from the axis  24  (see  FIGS.  1  and  2   ). The end cap  110  and coupling  120  are in close proximity with or engaging the axial (top as shown) end of the core  28 . The tab  77  extends radially inward from the first tube  72  towards the axis  24 . The liner  71  can extend around the tab  77 . 
     A manifold  180  is secured to the stator  22  for helping route cooling liquid between the fluid reservoir  150  and all the cooling devices  70  in the rotary electric machine  20 . Referring to  FIGS.  5 - 6 B , the manifold  180  is annular and extends about an axis  182 . First and second cooling channels  190 ,  210  extend circumferentially about the axis  182  in a generally concentric manner. The first cooling channel  190  is positioned radially outward of the second cooling channel  210 . 
     The first cooling channel  190  extends from a first end  192  to a second end  194  spaced circumferentially from one another. An inlet passage  196  extends radially outward from the first end  192  and is fluidly connected to the fluid reservoir  150 . Cover plates  206  fluidly seal the first cooling channel  190 . In one example, the cover plates  206  are friction stir welded to the manifold  180 , i.e., the cover plates have a metallurgical bond with the manifold. 
     The second cooling channel  210  extends from a first end  212  to a second end  214  spaced circumferentially from one another. The first ends  192 ,  212  of the cooling channels  190 ,  210  are substantially radially aligned with one another. The second ends  194 ,  224  of the cooling channels  190 ,  210  are substantially radially aligned with one another. An outlet passage  216  extends radially outward from the first end  212  and is fluidly connected to the fluid reservoir  150 . Cover plates  226  fluidly seal the second cooling channel  210 . In one example, the cover plates  226  are friction stir welded to the manifold  180 . 
     Tubes  201 ,  221  are provided around the periphery of the manifold  180  and can extend axially therefrom. The tubes  201  receive the inlet tubes  130  of the cooling devices  70 . The tubes  221  receive the outlet tubes  140  of the cooling devices  70 . 
     Connecting passages  200  (see also  FIG.  6 C ) are provided in the manifold  180  and help to fluidly connect the inlet tubes  130  of the cooling devices  70  to the first cooling channel  190 . To this end, each connecting passage  200  extends radially through the manifold  180  from a first opening  202  fluidly connected to one of the tubes  201  associated with a respective cooling device  70  to a second opening  204  fluidly connected to the first cooling channel  190 . In one example, the second openings  204  can be arranged in an annular pattern about the axis  182  (see  FIG.  6 A ). 
     Similarly, connecting passages  220  help to fluidly connect the outlet tubes  140  of the cooling devices  70  to the second cooling channel  210 . To this end, each connecting passage  220  extends radially through the manifold  180  from a first opening  222  fluidly connected to one of the tubes  221  associated with a respective cooling device  70  to a second opening  224  fluidly connected to the second cooling channel  210 . In one example, the second openings  224  can be arranged in an annular pattern about the axis  182  (see  FIG.  6 A ). The manifold  180  therefore fluidly connects the inlet and outlet tubes  130 ,  140  of every cooling device  70  in the rotary electric machine  20  to the fluid reservoir  150 . 
     In operation (see  FIGS.  6 A and  6 C ), cooling fluid flows from the reservoir  150  and enters the manifold  180  through the inlet passage  196  in the manner M 1 . The cooling fluid then flows into the first end  192  of the cooling channel  190  and circumferentially about the axis  182  in the manner M 2 . This allows the cooling fluid to pass axially into every second opening  204  in the first cooling channel  190  in a parallel manner. From there, the cooling fluid flows radially outward through the connecting passages  200  to the first openings  202  in the manner M 3  and enters each cooling device  70  by flowing through the tubes  130 ,  201  into the passage  126  (see  FIG.  3 B ). Consequently, all the cooling devices  70  can be fluidly connected to one another in parallel via the second openings  204 . It will be appreciated, however, that one or more of the second openings  204  can be blocked or plugged (see also  FIG.  6 D ) to prevent cooling fluid from flowing therein and thereby prevent cooling fluid from flowing from the first cooling channel  190  to the cooling device(s)  70  associated with the blocked second opening(s). 
     The cooling fluid then passes through the passage  116  and into the passage  98  at the first end  94  of the second tube  92  (see  FIG.  3 C ). The cooling fluid flows downward (as shown) in the manner indicated by the arrow F 1  through the slot  32  and between the winding coils  40 . The cooling fluid exists the passage  98  at the second end  96  of the second tube  92  and is turned around in the gap  100  by the end cap  160 . 
     This configuration allows the cooling fluid to then pass upward (as shown) in the manner indicated by the arrow F 2  through the passage  78  in the first tube  72 . The cooling device  70  therefore provides for bidirectional flow of cooling liquid within the slot  32  associated therewith. It will be appreciated that the cooling liquid could also flow in the opposite direction, namely, in the direction F 1  through the tube  140  and in the direction F 2  through the tube  130 . 
     In either case, the cooling fluid flows in a U-shaped or substantially U-shaped loop entirely within the slot  32 . In other words, the cooling fluid does not exit the slot  32  between entering the second tube  92  and exiting the first tube  72 , thereby avoiding cooling loops around the teeth  30 . This helps reduce circulating currents and increase motor performance. 
     The cooling fluid then exits the passage  78  at the first end  74  of the first tube  72 , flows through the passages  118 ,  128 , and exits the cooling device  70  through the tube  140 . Referring back to  FIG.  6 C , the cooling fluid then passes into the first opening  222  via the tube  221 , flows through the connecting passage  220  in the manner M 4 , and enters the second cooling channel  210  through the second opening  224 . This is repeated for every cooling device  70  such that cooling fluid exits all the cooling devices  70  and flows into the second cooling channel  210  in the manifold  180  in a parallel manner. 
     When one or more of the second openings  204  is blocked or plugged ( FIG.  6 D ), a bypass tube  251  can connect the tube  221  associated with one cooling device  70  with the tube  201  of the circumferentially adjacent cooling device. As a result, the cooling fluid exiting one cooling device  70  flows to the bypass tube  251  in the manner indicated by the arrow S into the adjacent cooling device rather than returning to the manifold  180 . That said, the cooling devices  70  connected by the bypass tubes  251  are fluidly connected in series with one another. This serial connection continues until the cooling liquid reaches a tube  211  fluidly connected to the second cooling channel  210  instead of a bypass tube  251 . Once the cooling fluid flows from any tube  211  to the second cooling channel  210 , the cooling fluid then flows circumferentially about the axis  182  through the second cooling channel in the manner M 5  to the outlet passage  216  and back to the reservoir  150  in the manner M 6 . 
     The cooling fluid can flow in the same direction in the first and second cooling channels  190 ,  210 , e.g., clockwise as viewed in  FIG.  6 A . The cooling channels  190 ,  210 , first openings  202 ,  222 , and second openings  204 ,  224  are configured to provide balanced fluid flow through the manifold  180 . More specifically, the manifold  180  is configured such that all the cooling devices  70  experience the same or substantially the same pressure drop and flow rates therethrough. To this end, the total length of the fluid flow path in the manifold  180  to and from each cooling device  70  is substantially the same throughout the rotary electric machine  20 . 
     For example and referring to  FIG.  6 B , when cooling fluid enters the manifold  180  through the inlet passage  196 , a flow path P 1  associated with a first cooling device (not shown) extends within the first cooling channel  190  from the inlet passage to a second opening  204   a  (the suffix “a” being added for clarity) associated with the inlet tube  130  of the first cooling device. After flowing through the first cooling device  70 , the cooling fluid flows along a flow path P 2  within the second cooling channel  210  from the second opening  224   a  associated with the first cooling device to the outlet passage  216 . The flow paths P 1 , P 2  extend a total circumferential distance C through the manifold  180  and about the axis  182 . 
     Similarly, a flow path P 3  associated with a second cooling device  70  (not shown) extends within the first cooling channel  190  from the inlet passage  196  to a second opening  204   b  associated with the inlet tube  130  of the second cooling device. After flowing through the second cooling device, the cooling fluid flows along a flow path P 4  within the second cooling channel  210  from the second opening  224   b  associated with the second cooling device to the outlet passage  216 . The flow paths P 3 , P 4  extend the total circumferential distance C through the manifold  180  and about the axis  182 . Every remaining cooling device  70  connected to the manifold  180  has the same or substantially the same flow path distance C through the cooling channels  190 ,  210 . Consequently, the cooling path through the manifold  180  associated each cooling device  70  will have the same pressure drop. This is facilitated by positioning the openings  202 ,  222  in substantial radial alignment with the openings  204 ,  224  for each cooling device  70  and/or positioning the inlet and outlet passages  196 ,  216  in close proximity with one another. 
     In addition to using cooling fluid to help cool the winding coils  40 , the manifold  180  shown and described herein is also configured to help cool a rotor  250  (see  FIGS.  7 A- 7 B ) of the rotary electric machine  20 . The rotor  250  is secured to and rotatable with a shaft  252  about an axis  254 . A bearing  258  connected to the shaft  252  is mounted to the stator  22  (not shown) such that the axes  24 ,  254  are coaxial. Consequently, the rotor  250  rotates about the axis  24  within and relative to the stator  22 . 
     A fan  260  is fixed to the shaft  252  and therefore rotates with the rotor  250 . The fan  260  includes an annular base  262  extending about and centered on an axis  264 . Fins or blades  266  are provided on the base  262  and extend radially towards the axis  264 . The number of blades  266  can be equal to or different from the number of slots  32  in the stator  22 . In one example, the number of blades  266  is not a common multiple of the number of slots  32 . The number of blades  266  can also not be a common multiple as the number of magnetic poles in the stator  22 . In another example, the number of blades  266  is a prime number. 
     It will be appreciated that changing the number of blades  266  affects the acoustic noise of the fan  260 . More specifically, if the number of blades  266  is a common multiple with the number of slots  32 , for instance, then some number of blades will pass by slots at the same time, causing a distinct and audible frequency proportional to the motor speed. That said, changing the number of blades  266  so that there is never more than one blade passing a slot  32  at the same time greatly reduces the audible noise. 
     The direction of radial extension of the blades  266  can intersect the axis  264  or be offset/spaced therefrom. Each blade  266  can have a rectangular shape and a thickness in the circumferential direction that is constant along its length or variable (not shown). The blades  266  can be straight (as shown) or curved (not shown). Tabs  268  extend radially inward from the base  262  and receive fasteners (not shown) for securing the fan  260  to the shaft  252 . 
     With this in mind, fins  230  (see  FIGS.  5  and  8   ) extend axially away from the manifold  180  and are arranged in an annular pattern about the axis  182 . The fins  230  are formed from a thermally conductive material and collectively encircle the rotor  250 . When the rotor  250  includes permanent magnets, it is desirable to limit the temperature thereof in an effort to maintain their strength and help prevent demagnetization. When the rotor  250  includes copper bars, it is desirable to limit the temperature thereof to reduce electrical resistance and increases efficiency. 
     In either case, rotation of the shaft  252  attached to the rotor  250  in the manner indicated by the arrow R in  FIG.  8    rotates the fan  260  secured thereto. The rotating fan  260  creates a pressure differential that generates airflow A around and along the rotor  250 . More specifically, the fan  260  draws in air axially (“up” as shown) through axial openings in the rotor  250  and returns the air (“down” as shown) through the radial air gap between the rotor and the stator  22 . Since the fan  260  is secured directly to the shaft  252 , increasing the shaft rotation speed likewise increases the fan rotation speed. 
     The airflow A passes over and through the fins  230  in the manifold  180 . As a result, heat generated in the rotor  250  is removed by forced convection from the fan  260  and transferred into the colder manifold  180 . The removed heat then passes through the manifold  180  to the cooling fluid flowing in one or both cooling channels  190 ,  210 . The degree of heat convection out of the circulating airflow A and into the cooling liquid is proportional to the surface area of the fins  230  and, thus, the fins can be designed and configured to provide a desired degree of cooling of the rotor  250 . 
     Moreover, heat removal from the circulating airflow A occurs while the manifold  180  is circulating cooling fluid between the fluid reservoir  150  and the cooling devices  70 . Consequently, the cooling fluid is also capable of removing heat from the circulating airflow A around the rotor  250 , thereby enabling the manifold  180  to act as a heat exchanger with not only the cooling devices  70  in the stator  22  but also with the rotor. More specifically, heat can be removed from the circulating airflow A and passed through the manifold  180  to the cooling fluid flowing in one or both cooling channels  190 ,  210 . 
     The manifold  180  is also configured to help cool the motor connections  280 ,  290  during operation of the rotary electric machine  20 . The motor connections  280 ,  290  are electrically insulated from the manifold  180 . Referring back to  FIG.  1   , since the motor connections  280 ,  290  are axially aligned with the cooling channels  190 ,  210  heat generated during operation of the motor connections can pass through the manifold  180  and/or cover plates  206 ,  226  into the cooling liquid in one or both cooling channels. The alignment and close proximity of the motor connections  280 ,  290  with the cooling channels  190 ,  210  allows the cooling liquid therein to remove a large percentage of the heat generated by the motor connections, e.g., up to about 80% of the generated heat. 
     What have been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.