U.S. patent application number 11/113927 was filed with the patent office on 2005-10-27 for motor frame cooling with hot liquid refrigerant and internal liquid.
Invention is credited to Ayers, Curtis W., Coomer, Chester, Hsu, John S..
Application Number | 20050235672 11/113927 |
Document ID | / |
Family ID | 35135034 |
Filed Date | 2005-10-27 |
United States Patent
Application |
20050235672 |
Kind Code |
A1 |
Hsu, John S. ; et
al. |
October 27, 2005 |
Motor frame cooling with hot liquid refrigerant and internal
liquid
Abstract
This invention presents the device and method for cooling
electric machines with hot liquid refrigerant in a floating
refrigerant loop and using an internal liquid such as oil for
enhancing the cooling effects. The electric machine cooling
apparatus has at least one refrigerant tube disposed in the
electric machine. The refrigerant tube is in thermal communication
with the electric machine. An internal liquid is disposed inside
the frame of the electric machine. The internal liquid is in
thermal communication with the electric machine and at least one
refrigerant tube. The refrigerant is at least partially a hot
liquid refrigerant supplied from a floating refrigerant loop.
Inventors: |
Hsu, John S.; (Oak Ridge,
TN) ; Ayers, Curtis W.; (Kingston, TN) ;
Coomer, Chester; (Knoxville, TN) |
Correspondence
Address: |
UT-Battelle, LLC
P.O. Box 2008
Oak Ridge
TN
37831-6258
US
|
Family ID: |
35135034 |
Appl. No.: |
11/113927 |
Filed: |
April 25, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60565461 |
Apr 26, 2004 |
|
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Current U.S.
Class: |
62/259.2 ;
62/505 |
Current CPC
Class: |
H02K 9/19 20130101; H02K
5/20 20130101 |
Class at
Publication: |
062/259.2 ;
062/505 |
International
Class: |
F25D 023/12; F25B
031/00 |
Goverment Interests
[0002] This invention was made with United States Government
support under Contract No. DE-AC05-00OR22725 between the United
States Department of Energy and U.T. Battelle, LLC. The United
States Government has certain rights in this invention.
Claims
We claim:
1. An electric machine cooling apparatus comprising; an electric
machine having a frame, stator, and rotor, at least one refrigerant
tube disposed in said electric machine, said refrigerant tube in
thermal communication with said electric machine, an internal
liquid disposed inside the frame of said electric machine, said
internal liquid in thermal communication with said electric machine
and said at least one refrigerant tube, wherein the refrigerant
in,said at least one refrigerant tube is at least partially a hot
liquid refrigerant supplied from a floating refrigerant loop.
2. An electric machine cooling apparatus according to claim 1
wherein said internal liquid is selected from the group consisting
of transmission oil and lubrication oil.
3. An electric machine cooling apparatus according to claim 1
wherein said refrigerant tube material is at least one material
selected from the group consisting of copper and aluminum.
4. An electric machine cooling apparatus according to claim 1
wherein said at least one refrigerant tube further comprises at
least one surface enhancement selected from the group consisting of
fins, pins, and re-entrant cavities.
5. An electric machine cooling apparatus according to claim 1
wherein said frame further comprises ribs.
6. An electric machine cooling apparatus according to claim 1
wherein said tubes are disposed having a gap between said tubes and
said frame.
7. An electric machine cooling apparatus according to claim 1
wherein said rotor further comprises at least one end piece to
sling internal liquid droplets into contact with internal surfaces
of said electric machine.
8. An electric machine cooling apparatus according to claim 7
wherein said at least one end piece further comprises at least one
scooper.
9. An electric machine cooling apparatus according to claim 7
wherein said at least one end piece further comprises at least one
scooper with grooves.
10. An electric machine cooling apparatus according to claim 7
wherein said at least one end piece further comprises a wavy
surface.
11. An electric machine cooling apparatus according to claim 7
wherein said at least one end piece further comprises a wavy
surface with grooves.
12. An electric machine cooling apparatus according to claim 1
wherein said internal liquid is in communication with a
transmission sump.
13. An electric machine cooling apparatus according to claim 12
wherein communication between said internal liquid and said
transmission sump is controlled using a ball valve.
14. A method for cooling an electric machine comprising; flowing
refrigerant through at least one refrigerant tube disposed in an
electric machine having a frame, stator, and rotor; said
refrigerant tube in thermal communication with said electric
machine, slinging an internal liquid disposed inside the frame of
said electric machine, said internal liquid in thermal
communication with said electric machine and said at least one
refrigerant tube, wherein the refrigerant in said at least one
refrigerant tube is at least partially a hot liquid refrigerant
supplied from a floating refrigerant loop.
15. A method according to claim 14 wherein said internal liquid is
selected from the group consisting of transmission oil and
lubrication oil.
16. A method according to claim 14 wherein said refrigerant tube
material is at least one material selected from the group
consisting of copper and aluminum.
17. A method according to claim 14 wherein said at least one
refrigerant tube further comprises at least one surface enhancement
selected from the group consisting of fins, pins, and re-entrant
cavities.
18. A method according to claim 14 wherein said frame further
comprises ribs.
19. A method according to claim 14 wherein said tubes are disposed
having a gap between said tubes and said frame.
20. A method according to claim 14 wherein said rotor further
comprises at least one end piece disposed to sling internal liquid
droplets into contact with internal surfaces of said electric
machine.
21. A method according to claim 20 wherein said at least one end
piece further comprises at least one scooper.
22. A method according to claim 20 wherein said at least one end
piece further comprises at least one scooper with grooves.
23. A method according to claim 20 wherein said at least one end
piece further comprises a wavy surface.
24. A method according to claim 20 wherein said at least one end
piece further comprises a wavy surface with grooves.
25. A method according to claim 14 wherein said internal liquid is
in fluid communication with a transmission sump.
26. A method according to claim 25 wherein fluid communication
between said internal liquid and said transmission sump is
controlled using a ball valve.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application 60/565,461 filed Apr. 26, 2004, and is herein
incorporated by reference. This application is related to U.S.
patent application Ser. No. 10/926,205 filed Aug. 25, 2004, and is
herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0003] For vehicles using electric motors and power electronic
inverters, two-phase cooling with the coolant changed from the
liquid phase to the vapor phase is far more effective than using
single-phase such as liquid to liquid heat transfer. The
significant latent heat associated with the two phase heat transfer
is the reason for making two-phase cooling attractive. This type of
cooling addresses the need for increased power density and
associated higher heat fluxes in inverters and traction drive
motors.
[0004] There are various water cooled stator frames available. The
pressure that the water jacket can take is not as high as what a
certain refrigerant such as R134a takes, as well as potential
porosity problems in aluminum castings causing leaks under high
pressure. A totally new concept of the electric machine frame
design is presented in this invention.
[0005] The single phase cooling cannot be totally removed even in a
two-phase cooling system. For example, in a motor the heat loss
produced in the stator winding still needs to go through a
single-phase heat transfer (i.e. thermal conduction) before
reaching to the two-phase cooling zone. This invention presents a
method that can enhance both the two-phase and the single-phase
heat transfer arrangements.
[0006] U.S. Pat. No. 5,271,248, issued to Crowe on Dec. 21, 1993,
teaches a dual cooling system for motors that removes heat using a
standard refrigerant cycle and heat exchangers.
BRIEF DESCRIPTION OF THE INVENTION
[0007] This invention presents the device and method for cooling
electric machines with hot liquid refrigerant in a floating
refrigerant loop and using an internal liquid such as oil for
enhancing the cooling effects. The electric machine cooling
apparatus has at least one refrigerant tube disposed in the
electric machine. The refrigerant tube is in thermal communication
with the electric machine. An internal liquid is disposed inside
the frame of the electric machine. The internal liquid is in
thermal communication with the electric machine and at least one
refrigerant tube. The refrigerant is at least partially a hot
liquid refrigerant supplied from a floating refrigerant loop.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is an embodiment showing tubes cast in a frame and
internal liquid level inside an electric machine.
[0009] FIG. 2 has tubes cast in the frame with certain tube
portions exposed inside the frame.
[0010] FIG. 3 is a perspective view of a refrigerant tubing
layout.
[0011] FIG. 4 is a sample frame for a HSUB motor with the wound
stator core having right and left bearing brackets, additional
axial excitation coils with cooling holes, and internal liquid.
[0012] FIG. 5 is a sample rotor.
[0013] FIG. 6 shows minimal internal liquid level changes for a
horizontal machine mounted perpendicular to the vehicle's travel
direction.
[0014] FIG. 7 shows internal liquid level changes for a horizontal
machine as vehicle tilts to the left or right.
[0015] FIG. 8 shows the internal liquid scooper with or without
grooves.
[0016] FIG. 9 shows a wavy surface, with or without grooves, formed
into the end piece for internal liquid pick-up.
[0017] FIG. 10 is an example using a ball valve for controlling
crossover flow.
DETAILED DESCRIPTION OF THE INVENTION
[0018] FIG. 1 shows an embodiment of the invention using tubes 11
cast in a frame 12 and internal liquid level 14 inside electric
machine 10 for combined two-phase and single-phase cooling. Metal
tubes withstand the high pressures required by the hot liquid
refrigerant flowing in the frame 12. An internal liquid 16 such as
a transmission or lubrication oil is filled at the bottom of the
frame 12. Hot liquid refrigerant 17 enters the electric machine 10
from a floating refrigerant loop (not shown) as described in
co-pending U.S. patent application No. 60/565,461 filed Apr. 26,
2004, herein incorporated by reference, and hot vapor refrigerant
18 exits the electric machine 10 returning to the floating
refrigerant loop. The hot vapor refrigerant 18 that exits the
electric machine 10 can be a mixture of refrigerant vapor and
liquid depending on the heat load imposed by the electric machine.
The floating refrigerant loop can be a stand-alone loop having a
dedicated pump and condenser. Or, the floating refrigerant loop can
be integral with the vehicle refrigeration system.
[0019] The frame 12 can be tied to the floating refrigerant loop
for the total thermal management system as taught in U.S. patent
application Ser. No. 10/926,205 filed Aug. 25, 2004, entitled
"Floating Loop System for Cooling Integrated Motors and Inverters
Using Hot Liquid Refrigerant", and U.S. Pat. No. 6,772,603 issued
to Hsu et al. Aug. 10, 2004, both herein incorporated by reference.
The pump (not shown) in the floating refrigerant loop pumps hot
liquid refrigerant 17 into the electric machine 10 and heat is
transferred from the internal liquid and the frame 12 into the
refrigerant to evaporate the refrigerant before leaving the
electric machine as hot vapor refrigerant 18. The hot vapor
refrigerant 18 is cooled and condensed in a condenser (not
shown).
[0020] FIG. 2 shows more details about the frame 12. The metal
tubes 22 are partially exposed inside the electric machine frame
12. The arrangement allows the frame 12 to be sand cast or die
cast. Various metal tubes such as copper and aluminum tubes can be
used as long as the casting does not damage the mechanical strength
of the tube. The hot liquid refrigerant 17 inlet side of the
individual tubes can be welded or brazed together to form a single
fitting. The same manner can be used for the hot vapor refrigerant
18 outlet side of the tubes. Ribs 24 are cast in the frame 12 to
allow certain portions of the tubes 22 to be exposed inside of the
frame. Very small gaps may exist between the tubes 22 and the frame
12. Certain portions of the tubes may make direct contact with the
frame. Heat transfer of the inner surface and the outer surface of
the tubes can be enhanced by adding commonly known surface
treatments such as fins, pins, and reentrant cavities. These
enhancements can be applied to the entire tubes or to portions of
the tubes for obtaining the most heat transfer improvements.
[0021] As an example the layout of the refrigerant tubes 22 is
conceptually shown in FIG. 3. In practice, all the sharp bends of
the tubes 22 should be in reasonably large radii for reducing the
flow resistance.
[0022] FIG. 4 shows a sample frame with wound stator core 41, right
42 and left 44 bearing brackets, additional axial excitation coils
46 with cooling holes 47, and cooling internal liquid level 48. For
conventional machines no additional axial excitation coils exist.
The induction motors may have rotor windings in a squirrel cage
form. The figure serves as an example to show that possible heat
sources can come from both radial and axial directions. The cooling
of other components inside the frame such as the excitation coils
of a HSUB machine can be achieved through the liquid droplets. As
shown in FIG. 4 the excitation coil 46 is situated inside the
bearing brackets 42, 44. The internal liquid 48 can cool the
bearing bracket. The cooling holes 47 around the bearing brackets
allow the liquid to sip into the excitation coil 46 for a better
thermal dissipation.
[0023] Because very small gaps may exist between the tubes and the
frame, an internal liquid such as a transmission or lubrication oil
is filled at the bottom of the frame. The rotor 52 having a shaft
54 shown in FIG. 5, as an example, picks up a small portion of the
internal liquid (oil) at the internal liquid level 58 and slings
internal liquid droplets to the stator coils, parts inside the
frame, and to the exposed tubes. The internal liquid will fill up
the gap between the tube and the frame through capillary effect.
This helps the two-phase heat transfer in the tubes as well as the
cooling of the windings and coils inside the electric machine. The
motor frame can dissipate the heat coming out from the stator core
and the liquid droplets can carry the heat from the winding end
turns and the other components inside the frame back to the sump
for cooling. The liquid droplets are cooled down in inside of frame
and in the frame sump for recirculation.
[0024] Because when the electric machine is mounted in a vehicle,
the cooling liquid level inside the frame changes according to the
angle of the vehicle. FIG. 6 shows that if the machine is
horizontally mounted but is perpendicular to the vehicle's
traveling direction, the internal liquid level 68 changes very
little when the vehicle goes uphill or downhill.
[0025] FIG. 7 shows that the internal liquid level 78 changes more
for a horizontal machine mounted along the vehicle's traveling
direction. The surface of the end pieces of the rotor must be
smooth except the regions close to the outer diameter of the end
pieces with various pick up arrangement. This lowers the drag
produced between the rotor end pieces and the liquid, while
allowing distribution of fluid to upper portion of the windings,
motor frame, and cooling tubes.
[0026] The machine frame can be used as a heat sink for cooling
components that are not suitable to be cooled directly by the
refrigerant liquid and vapor.
[0027] In order for the rotor to pick up the liquid without a
strong drag, various slingers for producing liquid droplets inside
the frame are disclosed. For a very high speed motor, a smooth
rotor surface might do the job sufficiently. For a relatively lower
speed motor FIGS. 8 and 9 provide certain options.
[0028] FIG. 8 shows that the outer periphery of the rotor 82 end
pieces 84 contains certain scoopers 85 with or without grooves 86
for picking up the liquid 88 and slinging it. The depth of the
scooper and the size and number of the grooves 86 depends on the
speed of the rotor 82. The depth and the number of the grooves 86
reduce if the speed is high for the drag reduction.
[0029] FIG. 9 shows the outer periphery of the rotor 92 end pieces
94 having a wavy surface 96 with or without grooves 98. The depth
and size of the wavy surface 96 and the size and number of the
grooves 98 depends on the speed of the rotor. The depth, size, and
number of the grooves reduce if the speed is high for the drag
reduction.
[0030] There are two options for supplying internal liquid to the
electric machine: one is a dedicated internal liquid supply for the
electrical machine, the other ties the internal liquid sump 104
with the transmission oil sump 106 for fluid communication. The
liquid level for the tied-together option is only balanced slowly
between the internal liquid sump 104 and the transmission sump 106
when the vehicle is in a level position. This discourages the
temperature exchange between the two sumps. With the internal
liquid shared with the transmission liquid system, a free liquid
circulation between the machine and the transmission system is
discouraged because the transmission liquid (oil) temperature is
normally at a higher temperature (around 85.degree. C.) than the
internal liquid temperature (can be below 55.degree. C.) inside the
electrical machine. FIG. 10 shows an example for controlling
crossflow between the internal liquid sump 104 and the transmission
sump 106 by using a ball valve 102. When the motor is tilted the
ball valve 102 stops the crossover flow. When the motor is level a
slow flow is allowed.
[0031] The invention has been described in terms of specific
embodiments which are indicative of a broad utility but are not
limitations to the scope of the invention. Additions and
modifications apparent to those with skill in the art are included
within the scope and spirit of the invention.
* * * * *