FIELD OF INVENTION:
The present invention relates to cooling fan induction motor for electric vehicles
applications. Heat is generated in armature and stator cores of every induction motor
during operation due to electrical resistance. The generated heat needs to be
dissipated in order maintain the temperature with in certain limits for protecting
winding from overheating and better performance of the motor. In case present
induction motor system for electric vehicle application, the generated heat in armature
is carried away by air which indirectly interacts with liquid coolant in the stator. Air is
recirculated in closed circuit and the liquid coolant is cooled outside the motor. In order
to recirculate the air in closed circuit, the required head rise is provided by a centrifugal
fan which is mounted on the rotor shaft end inside of the motor. The present invention
is more particularly relates to high efficiency high flow 2D centrifugal fan with flow
coefficient of 0.25.
BACKGROUND OF THE INVENTION:
In the existing art, cooling fans for induction motor of electric vehicle application is
required to handle large volume of flow to extract the heat from rotor and stator
windings to maintain the temperature within the allowable range. Moderate pressure
rise across the fan also required to overcome the cooling circuit resistance and to main
the flow rate required for cooling of windings.
High flow 2D centrifugal fan comprises single disc namely hub and a plurality of blades
disposed on the disk equidistantly in a circumferential direction to define the open flow
passage by means of hub disc and blades. The geometric configuration of the fan
blading significantly affects the aerodynamic performance, due to the fact that, the
geometric characteristics of the blade determine the distribution of the relative
velocities of the fluid flow along the fan, diffusion of fluid within the fan, blade to blade
loading at hub and intermediate planes and flow passage area distribution that affects
the flow behaviour in the flow path and various internal and external losses. Inlet

diameter of blades, exit diameter blades, width of the blade at inlet and width of the
blade at exit determines the flow rate that will handled by the fan apart from its
operating speed.
One of the main demands from the induction motor of electric vehicles is high volume
of flow with flow coefficient of 0.25 which will not fall into the category of centrifugal
fans but into axial fans. Optimization of fan blades angles for head rise and
optimization of fan blade inlet diameter and width and exit diameter and width has
been are required. None of the prior arts discussed about the high flow requirement,
pressure rise and efficiency requirements. It is required to develop a high flow 2D fan
to meet the requirements of induction motor for electric vehicles.
Patents related to the centrifugal cooling fan are given below,
[1] US 4,566,864 28/01/1986 Yosizi Yamamoto,Kariya, Japan;
[2] US 5,144,175 01/09/1992 Jack L. Craggs, Cincinnati, Ohio;
[3] US 3,075,106 22/01/1963 Jerome N C Chi, New York;
A flattened electric motor, wherein there is fixed to one of two divided housings a
shaft, on which there is rotatably supported a rotor to which a flattened armature coil
is joined and to which the blowing fan is fixed through a radiating member is presented
in Ref [1]. Heat generated in the armature coil is transferred through the rotor to the
radiating member and it is radiated into the air.
A rotor for an induction motor, comprising a rotor core and an end connector with
plurality of spaced fan blades on it is presented in Ref. [2]. Each of the fan blades has
backward curving inner and outer surfaces, with the outer surface substantially
perpendicular to the end connector.
A unidirectional electric motor arranged in the motor chamber comprising, a stator
including a core having winding, a rotor having an fan formed with a plurality of

angularly spaced apart blades to direct a cooling fluid into contact with winding end
turns to dissipate the heat generated in order to maintain the temperature rise is
reported in Ref. [3].
The present invention differs from the prior arts on several counts and the efficiency
achieved is higher than the existing 2D fan of same flow coefficient. The salient feature
of the present invention vis-a-vis the prior art [1], [2] and [3] are described below.
a. Prior art Ref. [1], is electric cooling fan externally mounted to conduct the heat
from source to radiating member. The present invention is integrally mounted
inside the electric motor casing as part of closed cooling circuit and the details
of the prior art and present invention are shown in Fig.1 and Fig.2 respectively.
The purpose of the fan is entirely different.
b. Prior art Ref. [1], There is no indirect liquid cooling and details of the fan are
not available whereas the present invention works in combination of liquid
cooling and the complete fan details are furnished here with. The present
invention is a two dimensional fan with backward curved blades with inlet angle
(-) 35 deg. and exit angle of (-) 25 deg. and the flow co-efficient of fan is 0.25.
c. Prior art Ref. [1], geometrical details of fan like blade angle distribution, wrap
angle distribution diameter, etc. are not specified.
d. Prior art Ref. [2], cooling fan is not a separate a one but fan blades are integrally
casted on end connectors of electric motor. It is more particularly relates to
improved rotor and end connectors for induction motors having fan blades on
rotor end for maximizing the efficiency.
e. Prior art Ref. [2] Cooling circuit is an open circuit and there is no in direct liquid
cooling. Fan blade angle at inlet is 20 to 40 deg. The details of the Ref. [2] are
shown in Fig. 3. The present invention has the fixed blade angles of (-) 35 deg.
at inlet and (-) 25 deg. at exit.
f. Prior art Ref. [2], geometrical details of fan like blade angle distribution, wrap
angle distribution diameter, etc. are not specified.

g. Prior art Ref. [3], relates to dynamoelectric machines and more particularly is
concerned with improvements in an arrangement for cooling electric motors of
hermetic refrigeration motor compressor units.
h. Prior art Ref. [3], cooling fan is not a separate a one but fan blades are integrally
casted on end connectors of electric motor.
i. Prior art Ref. [3], There is no indirect liquid cooling and details of the fan are
not available whereas the present invention works in combination of liquid
cooling and the complete fan details are furnished here with.
j. Prior art Ref. [3], geometrical details of fan like blade angle distribution, wrap
angle distribution diameter, etc. are not specified. The details of the prior art
are shown in Fig.4.
k. The prior art Ref. [1], [2] and [3], though it is of the same interest of improving
the cooling of induction motor, the methodology followed in the present
invention is liquid and air cooling whereas in case of all prior arts, it is only air
cooling. Prior arts, details of fan geometry in terms of the blade angle
distribution, wrap angle distribution are not mentioned. In case of present
invention, the geometry is clearly defined in the form of blade angle distribution,
wrap angle distribution. and blade passage area distribution. Present invention
is tested and performance has been proved in the laboratory. This is clearly
vindicating the present invention is entirely different from all the referred prior
arts. The concept of induction motor for electrical vehicles application itself is a
latest concept and more relevant prior arts could not be found.
One or more drawbacks of conventional systems and process for a method for
improving yield strength of a workpiece and an apparatus are overcome, and
additional advantages are provided through the apparatus and a method as claimed
in the present disclosure. Additional features and advantages are realized through the
technicalities of the present disclosure. Other embodiments and aspects of the
disclosure are described in detail herein and are part of the claimed disclosure.

OBJECTS OF THE INVENTION:
Considering the above criteria, following analysis have been envisaged to determine
the objective of invention:
The principal objective of the present invention is to provide a geometrical parameter,
i.e., blade angle distribution of high flow 2D fan along the meridional flow path from
the fan inlet to exit to achieve high aerodynamic efficiency and cooling effect in a
closed circuit for induction motor of electric vehicle.
Another object of the present invention is to provide geometrical parameter, i.e., blade
wrap angle distribution of high flow 2D fan along the meridional flow path from the
fan inlet to exit to achieve high aerodynamic efficiency and cooling effect in a closed
circuit for induction motor of electric vehicle.
Another object of the present invention is to provide geometrical parameter, i,e., fan
passage area distribution of high flow 2D fan to achieve high aerodynamic efficiency
and cooling effect in a closed circuit for induction motor of electric vehicle.
Another object of the present invention is to provide geometrical parameter, i,e., inlet
hub radius of high flow 2D fan to achieve high aerodynamic efficiency and cooling
effect in a closed circuit for induction motor of electric vehicle.
Another object of the present invention is to provide geometrical parameter, i,e., blade
width at exit of high flow 2D fan to achieve high aerodynamic efficiency and cooling
effect in a closed circuit for induction motor of electric vehicle.
Another object of invention is to provide circumferential pitch to reduce the frictional
losses with in the fan and improve the efficiency.
BRIEF DESCRIPTIONS OF THE ACCOMPANYING DRAWINGS
It is to be noted, however, that the appended drawings illustrate only typical
embodiments of the present subject matter and are therefore not to be considered for
limiting of its scope, for the invention may admit to other equally effective
embodiments. The detailed description is described with reference to the

accompanying figures. In the figures, the left-most digit(s) of a reference number
identifies the figure in which the reference number first appears. The same numbers
are used throughout the figures to reference like features and components. Some
embodiments of system or methods in accordance with embodiments of the present
subject matter are now described, by way of example, and with reference to the
accompanying figures, in which
Figure 1 shows a Fan of prior art Ref [1]
Figure 2 shows present invention with general arrangement and 2D Fan geometry.
Figure 3 shows Prior Art Ref. [2] where fan blades are integrally casted on end
connectors of electric motor.
Figure 4 shows Prior Art Ref. [3] where fan blades are integrally casted on end
connectors of electric motor.
Figure 5 shows 2D Fan blade angle distribution of present invention.
Figure 6 shows 2D Fan blade wrap angle “θ “distribution of present invention.
Figure 7 shows 2D Fan blade thickness distribution of present invention.
Figure 8 shows 2D Fan passage area distribution of present invention.
The figures depict embodiments of the present subject matter for the purposes of
illustration only. A person skilled in the art will easily recognize from the following
description that alternative embodiments of the structures and methods illustrated
herein may be employed without departing from the principles of the disclosure
described herein.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION:
It should be noted that the description and figures merely illustrate the principles of
the present subject matter. It should be appreciated by those skilled in the art that
conception and specific embodiment disclosed may be readily utilized as a basis for
modifying or designing other structures for carrying out the same purposes of the
present subject matter. It should also be appreciated by those skilled in the art that

by devising various arrangements that, although not explicitly described or shown
herein, embody the principles of the present subject matter and are included within
its spirit and scope. Furthermore, all examples recited herein are principally intended
expressly to be for pedagogical purposes to aid the reader in understanding the
principles of the present subject matter and the concepts contributed by the
inventor(s) to furthering the art and are to be construed as being without limitation to
such specifically recited examples and conditions. The novel features which are
believed to be characteristic of the present subject matter, both as to its organization
and method of operation, together with further objects and advantages will be better
understood from the following description when considered in connection with the
accompanying figures.
As used in the description herein and throughout the claims that follow, the meaning
of “a”, “an” and “the” includes plural reference unless &e context clearly dictates
otherwise. Also, as used in the description herein, the meaning of “in”' includes “in”
and “on” unless the context clearly dictates otherwise.
The terms "comprises", “comprising”, or any other variations thereof used in the
disclosure, are intended to cover a non-exclusive inclusion, such that a device, system,
assembly that comprises a list of components does not include only those components
but may include other components not expressly listed or inherent to such system, or
assembly, or device. In other words, one or more elements in a system or device
proceeded by “comprises... a” does not, without more constraints, preclude the
existence of other elements or additional elements in the system, apparatus or device.
These and other advantages of the present subject matter would be described in
greater detail with reference to the following figures. It should be noted that the
description merely illustrates the principles of the present subject matter. It will thus
be appreciated that those skilled in the art will be able to devise various arrangements
that, although not explicitly described herein, embody the principles of the present
subject matter and are included within its scope.

The present invention 2D fan is designed in as 2D impeller of compressor. The main
objects of invention are parameterised fan geometry and their definitions that control
the entire fan geometry are described in the following.
2D fan blade angle “β” distribution at hub surfaces along the fan inlet to exit is defined
in Fig. 5. This blade angle distribution completely controls the flow physics within the
fan like diffusion, pressure recovery coefficient, pressure loss coefficient, relative
velocity distribution, fan passage area distribution, flow pattern at fan exit and along
the downstream of fan and thereby efficiency and cooling effect in an induction motor
of electric vehicle. The fan blade angle variation along the percentage length of
meridional flow path “B” of the present invention is shown in Fig.5 Numerically the
blade angle variation is (-) 35 deg. to (-) 25 deg. for with respect to meridional plane.
2D fan wrap angle “θ” distribution at fan hub surfaces from fan inlet to exit influences
blade loading / relative velocity distribution, the pressure recovery, flow behaviour and
thereby efficiency and cooling effect in an induction motor of electric vehicle. The
present invention has the wrap angle distribution which increases uniformly from fan
inlet to fan exit for achieving higher efficiency as in Fig.6. Numerically the wrap angle
variation is 0.0 deg. to (-) 14.9 deg. for with respect to meridional plane. The fan wrap
angle variation of the present invention along percentage length of meridional flow
path “A” is shown in Fig.6.
Blade angel “β” distribution and warp angle “θ” distribution of present distribution is
designed considering space constraints of motor to achieve uniform flow behaviour
without any flow recirculation, low momentum zones and flow separations for better
efficiency and cooling of motor. This is evident from the Fig. 9 through relative velocity
distribution in the flow field.
Also, Blade angel “β” distribution and warp angle “θ” distribution of present distribution
is designed considering space constraints of motor to achieve better blade loading that

helps in achieving higher efficiency and cooling of motor. This can be seen in Fig. 10
through static pressure distribution on pressure and suction side of the fan blades.
Blade passage width at inlet and exit, passage area distribution and hub and shroud
contours along with Blade angel “β” distribution and warp angle “θ” distribution of
present distribution are designed considering space constraints of motor to achieve
uniform head rise in the fan from inlet to exit. This can be seen in Fig. 11 through
head rise from fan inlet to exit.
2D fan blades circumferential pitch in terms of degrees depends of the total number
of blade in the fan. The number of blades in the fan shows major impact on the peak
blade loading and total frictional losses. It is observed that low flow 2D fan requires
lesser number of fan blades whereas high flow fan demands more number of fan
blades to achieve proper blade loading which results in efficient flow behaviour. For
the present invention which is a high flow fan, the circumferential pitch is 40 deg. for
achieving better blade loading and lesser friction losses. This has ultimately resulted
higher efficiency and cooling effect in an induction motor of electric vehicle.
2D fan inlet radius ‟R1” shown in Fig.2 (c), influences the efficiency of compressor
stage. Higher inlet radius increases the inlet relative velocity. Increase in inlet velocity
reduces the fan diffusion and there by pressure recovery and fan efficiency. However,
the fan needs to handle higher flow which demands higher annulus area for reducing
the air velocity at inlet. Considering above all requirements, for the present invention
which is of 140 mm fan diameter with flow range of 70% to 130% of design flow, the
inlet diameter is 64.2 % of fan exit diameter.
2D Fan blade width at exit ‟B2” shown in Fig.2 (c), plays major role in achieving the
overall efficiency and cooling of an induction motor. Fan exit width influences diffusion,
flow associated problems like re-circulation, separation and low momentum zones. Fan
exit blade width is directly related to fan exit blade angle ‟β2b” and flow coefficient.

For the present invention with 140 mm fan exit diameter where the flow co-efficient
is high with the fan exit blade angle (-) 25 deg. the fan exit blade width is 18 mm.
Thickness of 2D fan blade especially in case of smaller size plays a major role as it
influences the inlet blockage, inlet losses and there by overall performance of the 2D
fan. The present invention blade thickness distribution of shown in Fig.8 which has
resulted in reduced inlet blockage and losses.
Fan passage area distribution is mainly responsible for diffusion with in the fan and
influences the fan efficiency. This passage area distribution varies from high flow to
low fans. Continuous increase in the fan passage area from fan inlet to exit along the
meridional flow path ensures conversion of kinetic energy in to pressure and also
eliminates recirculation zones with in the fan. The fan passage area distribution for
achieving the higher efficiency and cooling effect for present invention which is of high
flow is shown in Fig. 8.
The fan geometrical parameters along the meridional flow path from fan inlet to fan
exit like Blade angle, Wrap angle, Blade thickness distribution, Passage area, Inlet
radius, Exit radius, Fan blade inlet width, Fan blade exit width, Fan blade
circumferential pitch are finalised based on systematic design approach with the rich
design experience and extensive CFD analysis and performance testing of prototype
where the efficiency and cooling of induction motor of electric vehicle achieved is very
close to the theoretical results.
In case of prior art, no information is available regarding the blade angle distribution,
wrap angle distribution, slope distribution, curvature distribution and passage area
distribution from fan inlet to fan exit is not defined. In case of prior art where blade
angle distribution is defined is entirely different from present invention. Also no
information is available regarding the fan inlet radius and exit radius. These are the
major factors influenced the relative velocity distribution, blade loading, diffusion,
static pressure distribution, flow behaviour within the fan and further downstream

which ultimately results in higher efficiency of high flow 2D fan for induction motor of
electric vehicle. The rigorous CFD studies have revealed that scaling of fan up to 40%
upward and 40% downward can give the same performance while the ratios of other
fan geometrical parameter are maintained.
Each of the appended claims defines a separate invention, which for infringement
purposes is “reorganized as including equivalents to the various elements or limitations
specified in the claims. Depending on the context, all references below to the
“invention” may in some cases refer to certain specific embodiments only. In other
cases, it will be recognized that references to the “invention” will refer 1o subject
matter recited in one or more, but not necessarily all, of the claims.
Groupings of alterative elements or embodiments of the invention disclosed herein are
not to be construed as limitations. Each group member can be referred to and claimed
individually or in any combination with other members of the group or other elements
found herein. One or more members of a group can be included in, or deleted form,
a group for reasons of convenience and/or patentability. When any such inclusion or
deletion occurs, the specification is herein deemed to contain the group as modified
thus fulfilling the written description of all groups used in the appended claims.
With respect to the use of substantially plural and/or singular terms herein, those
having skill in the art can translate form the plural to the singular and/or from the
singular to the plural as is appropriate to the context and/or application. The various
singular/plural permutations may be expressly set forth herein for sake of clarity.
It still be understood by takes within the art that in general, terms used herein, and
especially in the appended claims (e.g., bodies of the appended claims) are generally
intended as “open” terms (e.g., the term “including” should be interpreted as
“including but not limited to,” the term “having” should be interpreted as “having at
least”, the term “includes” should be interpreted as “includes but is not limited to”
etc.)- It will be further understood by those within the art that if a specific number of
an introduced claim recitation is intended, such an intent will be explicitly recited in
the claim, and in the absence of such recitation no such intent is present. For example,

as an aid to understanding, the following appended claim may contain usage of the
introductory phrases “at least one” and “one or more” to introduce claims recitations.
However, the use of such phrases should not be construed to imply that the
introduction of a claim recitation by the indefinite articles “a” or “an” limits any
particular claim containing such introduced claim recitation to inventions containing
only one such recitation, even when the same claims includes the introductory phrases
“one or more” or “at least one” and indefinite articles such a “a” or “an” (e.g, “a”
and/or “an” should typically be interpreted to mean “at least one” or “one or more”);
the same holds true for the use of definite article used to introduce claim recitations.
In addition, even if a specific number of an introduced claim recitation is explicitly
recited, those skilled in the art will recognize that such recitation should typically be
interpreted to mean at least the recited number (e.g. the bare recitation of “two
recitations,” without other modifiers, typically mean at least two recitations, or two or
more recitations). Furthermore, in those instances where a convention analogous to
“at least one of the A, B and C, etc.” is used, in general such a construction is intended
in the sense one having skill in the art would understand the convention (eg. “a system
having at least one A, B and C etc. would include but not be limited to systems that
have A alone, B alone, C alone, A and B together, A and C together, B and C together,
and/or A, B and C together etc.). In those instances, where a convention analogous
to “at least one of A, B, or C, etc.” is used, in general such a construction is intended
in the sense one having skill in the art would understand the convention (e.g., “a
system having at least one of A, B or C” would include but not be limited to systems
that have A alone, B alone, C alone, A and B together, A and C together, B and C
together and/or A, B and C together etc.). It will be further understood by those within
the art that virtually any disjunctive word and/or phrase presenting two or more
alternative terms, whether in the description, claims, or drawings, should be
understood to contemplate the possibilities of including one of the terms, either of the
terms or both terms. For example, the phrase “A or B” will be understood to include
the possibilities of “A” or “B” or “A and B”.
The above description does not provide specific details of manufacture or design of
the various components. Those of skill in the art are familiar with such details, and

unless departures from those techniques are set out, techniques, known related art or
later developed deigns and materials should be employed. Those in the art are capable
of choosing suitable manufacturing and design details.
The technology used herein is for the expose of describing particular embodiments
only and is not intended to be limiting of the present disclosure. It will be appreciated
that several of the above-disclosed and other features and functions, or alternative
thereof, may be combined into other systems or application. Various presently
unforeseen or unanticipated alternatives, modification, variation, or improvements
therein.

WE CLAIM:
1. A cooling fan for an induction motor preferably for an electric vehicle comprising
a plurality of blades arranged to form
- blade angle distribution at inlet (-) 35 deg. and at exit of fan (-) 25 deg;
- fan blade wrap angle distribution at inlet 0.0 deg and exit of fan (-) 14.9 deg;
wherein the blade thickness at leading edge is 2 mm and maximum thickness
is 3.6 mm; and
wherein the fan passage area increases from inlet towards exit.
2. The cooling fan as claimed in claim 1, wherein the fan may be a 2D fan.
3. The cooling fan as claimed in claim 1, wherein the fan has an inner radius ‘R1’
and an outer radius of ‘B2’.
4. The cooling fan as claimed in claim 1, wherein the fan diameter is about 140
mm and fan exit width is about 18 mm.
5. The cooling fan as claimed in claim 3, wherein the fan blade width at inner and
outer radius as 15.6 % and 12.8 % of fan exit diameter.