U.S. patent number 3,579,162 [Application Number 04/880,619] was granted by the patent office on 1971-05-18 for winding duct construction for power transformer.
This patent grant is currently assigned to General Electric Company. Invention is credited to Sudhir D. Savkar.
United States Patent |
3,579,162 |
Savkar |
May 18, 1971 |
WINDING DUCT CONSTRUCTION FOR POWER TRANSFORMER
Abstract
The ducts between adjacent layers of windings are formed into a
plurality of longitudinal passageways of generally square cross
section. A flat strip of insulating material twisted about the
central longitudinal axis thereof is provided in each of the
passageways to augment the heat flow from the winding to the
coolant flowing in the passageway.
Inventors: |
Savkar; Sudhir D. (Scotia,
NY) |
Assignee: |
General Electric Company
(N/A)
|
Family
ID: |
25376682 |
Appl.
No.: |
04/880,619 |
Filed: |
November 28, 1969 |
Current U.S.
Class: |
336/57;
165/104.33; 165/104.31; 165/109.1; 336/60 |
Current CPC
Class: |
H01F
27/12 (20130101); H01F 27/322 (20130101) |
Current International
Class: |
H01F
27/12 (20060101); H01F 27/10 (20060101); H01F
27/32 (20060101); H01f 027/10 () |
Field of
Search: |
;336/55,57,58,60,61 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kozma; Thomas J.
Claims
I claim:
1. A forced convection cooling system for a power transformer
comprising:
a tank containing insulating liquid coolant,
a transformer immersed in said coolant, said transformer including
a winding, said winding being in the form of a plurality of layers
of wire having adjacent layers of said winding spaced to provide a
plurality of ducts, each duct extending from one end of the winding
to the other end thereof,
a radiator system for said coolant having an inlet end connected to
said tank adjacent one end of said windings and having an outlet
end connected to said tank adjacent the other end of said
winding,
pumping means connected in the fluid flow circuit including said
ducts and said radiator system, and
each of said ducts including a plurality of passageways, each
passageway including means for producing a vortical motion in the
fluid flowing through the passageway.
2. The combination of claim 1 in which said vortical motion
producing means is a flat strip twisted about the central
longitudinal axis thereof, the cylindrical surface representing the
locus of the longitudinal edges of said strip encompassing a major
portion of the volume of said passageway.
3. The combination of claim 2 in which each of said strips is
essentially tangent to three sides of said passageway.
4. The combination of claim 2 in which each of said passageways is
substantially square in cross section and the width of said stripes
being substantially equal to a side of said square.
5. The combination of claim 2 in which a plurality of insulating
spacers extend along the length of said winding in said duct to
space one layer of said winding from an adjacent layer, said
twisted tape being secured to one of said spacers at points of
tangency therewith.
6. The combination of claim 5 in which said twisted tape is an
insulator.
7. A liquid-cooled power transformer comprising:
a winding, said winding being in the form of a plurality of layers
of wire having adjacent layers of said winding in spaced
relationship to provide a plurality of ducts extending from one end
of said winding to the other end thereof,
each of said ducts including a plurality of passageways, each
passageway including means for producing a vortical motion to the
fluid adapted to flow therethrough.
8. The combination of claim 8 in which said ducts are oval in shape
and in which said passageways are substantially square in cross
section.
Description
WINDING DUCT CONSTRUCTION FOR POWER TRANSFORMER
The present invention relates to forced convection cooling systems
for power transformers, and in particular, to improvements in the
structure of the cooling ducts in the windings of the transformer
to augment the heat transfer from the windings to the liquid
coolant circulated in the ducts.
A typical forced oil and forced air-cooled power transformer
apparatus includes a tank filled with insulating oil coolant, a
power transformer immersed in the fluid, and a cooler or radiator
system having an inlet end coupled to one end of the tank adjacent
one end of the windings and an outlet end connected to the tank
adjacent the other end of the windings. The windings of the power
transformer are provided with a plurality of ducts each generally
rectangular shaped in cross section extending from one end of the
windings to the other thereof and each situated between adjacent
layers of the windings. A pump is provided to circulate the oil
coolant through the ducts and the cooler. A fan is provided in the
forced air-cooling circuit of the cooler to produce airflow over
the cooler or radiator tubes thereof to remove the heat from the
oil coolant. In such an arrangement as described, good heat
transfer is highly desirable between the windings and the oil
coolant circulating in the ducts as the oil coolant can be operated
at a temperature closer to the temperature of the windings and
hence the transformer can be operated at a higher power rating.
Such mode of operation with higher oil temperature also means that
the cooler can operate more efficiently in removing heat from the
oil due to larger temperature gradients existing between the cooler
tubes and the circulated air currents.
The present invention is directed to the reduction in the thermal
resistance between the windings and the cooling ducts of a
transformer to decrease the temperature drop necessary to drive a
given amount of heat from the conductors of the winding to the
coolant oil circulated in the ducts.
Accordingly, an object of the present invention is to provide a
structure for winding ducts of a power transformer for improving
the heat transfer between the windings and the oil flowing in the
ducts.
Another object of the present invention is to provide simple
structure of low cost requiring a minimum of modification of
existing duct structures for decreasing the thermal resistance
between the winding of a transformer and the coolant flowing in the
ducts.
In accordance with an illustrative embodiment of the present
invention as applied to a power transformer, there is provided a
plurality of passageways in the ducts formed between adjacent
layers of a winding of the transformer. In each of the passageways
are provided a means for imparting a vortical motion to the coolant
flowing therethrough. One form of such means is a flat insulating
strip twisted about the central longitudinal axis thereof. The
passageways are preferably generally square in cross section.
The novel features which are believed to be characteristic of the
present invention are set forth in the appended claims. The
invention itself, however, together with further objects and
advantages thereof may best be understood by reference to the
following description taken in connection with the accompanying
drawings wherein:
FIG. 1 is a plan view of a power transformer apparatus including a
tank in which the transformer is included and a cooler or radiator
connected thereto for cooling the liquid coolant in which the
transformer is immersed;
FIG. 2 is a front view of the transformer apparatus of FIG. 1;
FIG. 3 is an enlarged sectional view of a winding of the
transformer of FIG. 2 taken along section lines 3-3 showing an
embodiment of the present invention;
FIG. 4 is an enlarged developed view of a section of FIG. 4
included in the indicated dotted enclosure thereof; and
FIG. 5 is a side view of the section shown in FIG. 4.
Referring now to FIGS. 1, 2 and 3, there is shown a tank 10
containing an insulating liquid coolant 11, such as oil, in which a
power transformer 12 is immersed. Associated with the tank for the
purpose of cooling the oil therein is a cooler 13. The inlet end 14
of the cooler is connected to an upper portion of the tank 10
adjacent one end of the transformer 12 for receiving coolant that
has been heated by power dissipated in the transformer. The outlet
end 15 of the cooler, is connected to the inlet end of a
circulating pump 16, the outlet end of which is connected to a
lower portion of the tank 10 adjacent the other end of the
transformer. A ducting 17 is provided to channel the cooled coolant
from the pump 16 into the ducts located in the windings and core of
the transformer 12. The cooler 13 includes a plurality of radiator
tubes through which the liquid coolant flows. A fan 20 is provided
for forcing air or other suitable gaseous medium over the surface
of the cooler tubes to remove the heat in the coolant flowing
through the tubes. The power transformer 12 includes a core 21 and
windings 22 and 23. The core 21 includes a plurality of ducts 24,
only one of which is shown, extending from one end adjacent the
lower portion of the tank to the upper portion of the tank. Each of
the windings 22 and 23 includes a plurality of ducts 25, only one
of which is shown in each winding between adjacent layers of the
windings extending from one end to the other end thereof.
Reference is now made particularly to FIG. 3 which shows a
sectional view of winding 22 of the transformer taken along section
line 3-3. The winding includes a plurality of layers only two of
which, layers 30 and 31, are shown. The layers 30 and 31 are
maintained in spaced insulating relationship by a plurality of
insulating spacers 32, for example, made of wood or other suitable
insulating material to provide a generally rectangular shaped duct
25. Spacers 32 provide good mechanical support between adjacent
windings. Another group of insulating spacers 33 provide a proper
structural form to the duct 25, that is, they form a plurality of
passageways 34, each of generally square cross section. The spacer
33 may be made of wood or of stacked paper insulation.
Referring now particularly to FIGS. 4 and 5 there are shown
developed views of a portion of the duct included in the dotted box
35 of FIG. 3. FIG. 5 shows an elevation view of the section of FIG.
4. Each element of FIGS. 4 and 5 corresponding to elements of FIG.
3 has the same numerical designation. The duct 25 includes a
plurality of the wide spacers 32 preferably made of some material
such as wood or plastic to provide good support between adjacent
layers 31 and 32 of the windings and also includes a plurality of
narrow spacers 33 located between the wide spacers 32. The narrow
spacers 33 may be made of wood or other suitable material such as
paper. The narrow spacers are arranged to provide a plurality of
generally square cross section passageways 34 in the duct 25. In
each of such passageways is located a thin flat strip of insulating
material 36 twisted about the central longitudinal axis 37 thereof
and secured along the edge 38 or 39 thereof which is at points 40
tangent to an adjacent spacer. If desired, the strip 36 may be
secured to the ends of the passageway 34. The width of the strip 36
is made substantially equal to the side of the square passageway
34. Accordingly, the cylindrical surface representing the locus of
the longitudinal edges 38 and 39 of the strip 36 is tangent to the
four sides of the square passageway 34 and encompasses a major
portion of the volume of the passageway.
In the operation of the transformer system, power generated and
dissipated in the windings 22 and 23 of the transformer is cooled
by the oil flowing in the ducts 25. The oil is moved through the
passageways 34 of the ducts by the action of the pump 16. The
twisted flat strip 36 located in each of the passageways imparts a
vortical motion to the oil flowing therein. Such vortical motion
has two principal actions in improving the heat transfer from the
windings 22 and 23 to the oil flowing in the passageways 34. The
peripheral velocity of the vortical flow in the passageway is
greater than the mean flow of oil from one end of the other of the
passageway. Accordingly, as oil is flowing more rapidly over the
heat transfer surface of the windings and the passageways, a
greater amount of heat is transferred to the oil bringing the fluid
up to a temperature closer to the temperature of the windings. The
vortical motion also has the effect of forcing the heavier and
cooler oil in the passageways to the walls of the passageways where
it is most effective in removing heat from the windings adjacent
thereto. The vortical motion also has the effect of removing the
hot oil from the vicinity of the heated walls of the passageways.
Accordingly, the net effect of the actions described is to raise
the temperature of the oil flowing from the upper ends of the
passageways and the ducts of which they are a part. In addition,
the vortical motion produces turbulence in the fluid flow which
facilitates and promotes heat transfer to the fluid from the
windings. The hot oil flows into the inlet passageway of the cooler
13 where it is pumped through the tubes of the cooler by the pump
16. The fan 20 forces ambient air over the tubes of the cooler 13
to remove the heat therefrom. As the arrangement of the present
invention increases the temperature of the oil applied to the inlet
of the cooler 13 without raising the limit set for the winding
temperature, improved power handling capability is obtained in the
transformer system. In addition, as the cooler operates more
efficiently when the differential between the oil temperature and
the cooling air temperature is higher, the present arrangement
achieves a more efficient cooling in the airflow system.
I intend by the appended claims to cover all modifications that
fall within the true spirit and scope of my invention.
What I claim as new and desire to secure by Letters Patent of the
United States is:
* * * * *