DESC:FIELD OF INVENTON
This invention relates an electric motor. More particularly this invention relates to design of cooling system for an electric motor and its components.

BACKGROUD OF THE INVENTION
An electric motor is an electrical machine that converts electrical energy into mechanical energy in the form of rotational movement. Generally, an electric motor comprises a motor housing, a stator mounted on an inner wall of the motor housing, and a rotor located at the centre of the stator. The stator comprises winding coils. The rotor comprises magnets and spins at high speeds, providing rotational mechanical energy to the system. The heat generated in the stator is easily coming out through the motor housing by conduction as the stator is directly mounted on the housing of the motor. However, the heat generated in the rotor is difficult to take out since the rotor is rotating and bearings are the only means of direct contact to remove the heat; other means are through convection. Since heat removal through bearing contact is not a preferred option, rotor heat is mainly removed by convection by adding internal fans on the rotor, which churn the air and help to cool the rotor. However, this is not effectively cooling the electromagnets or permanent magnets and the air gap area; hence, temperature hotspots are created on these active parts and the air gap area, which eventually reduces the motor's performance or even damages the motor.

To solve the above problem, some prior arts have adopted the motor having rotors, which are provided with end plates which act for balancing and also churning the air inside motor. This helps a totally enclosed motor cooling the winding to avoid stagnant air inside the motor. However in this system, air is circulated along the axis of the rotor in two planes, resulting in the creation of air turbulence that affects heat transfers between the active parts of the rotor. Heat that exists in the rotor-stator air gap is not extracted in this system. In motors, cooling the magnet or electromagnet is one of the crucial things to avoid performance degradation or magnet demagnetization due to excess heating. Using such system, the rotor components (magnets and electromagnets) and air in the gap between rotor and stator heat up significantly and also take longer time to reach equilibrium temperature.

OBJECT OF THE INVENTION
The object of the invention is to solve the above-mentioned problems of the electric motor. More particularly, the object of the invention is to provide an electric motor with a cooling system that effectively cools the motor as well as its all components.

Another object of the invention is to design a cooling system for the motor that increases the heat dissipation from the motor.

Another object of the invention is to design a cooling system for the motor that increases the heat dissipation from the stator and the rotor of the motor.

Another object of the invention is to design a cooling system for the motor that increases the cooling of the magnets and electromagnets used in the motor to avoid performance degradation or permanent failure.

SUMMARY OF INVENTION
To avoid the problems mentioned above and achieve the objects, the applicant has developed an electric motor wherein; it comprises:
a) motor housing (2)
b) at least a stator stacks (4) attached to the motor housing (2)
c) a motor shaft (6)
d) at least a rotor stacks (5) axially attached to the motor shaft (6)
e) balancing plates (7,8) axially attached to the motor shaft (6) on both sides of rotor stacks (5)
f) a cavity (12) is provided between the motor housing (2) and the balancing plate (7)
g) a cavity (3) is provided between the motor housing (2) and the balancing plate (8)

The balancing plates (7, 8) and rotor stacks (5) are provided with a plurality of openings (14, 29 & 27) respectively to pass air through them, and the balancing plate (7) has a varying thickness and curved surface (19) and is provided with plurality of fins (15) to create a low pressure zone for sucking air through the cavity (12) and pass through the openings (14, 27 & 29);

The balancing plate (8) is provided with plurality of taper fins (20) to create a high pressure zone for sucking air from the openings (27, 29) and throwing air through the gap (13) between stator stacks (4) and rotor stacks (5) towards the cavity (12). Thus, it forms a loop (25) of air circulation to cool all parts of the motor (1), the stator stacks (4), and the rotor stacks (5) and magnets.

According to an embodiment of the invention, a cavity (3) is provided between motor housing (2) and the balancing plate (8).

According to one embodiment of the invention, the location of fins (15) are alternatively placed between the locations of openings (14) as seen from the outer face (16) of the balancing plate (7).

According to one embodiment of the invention, the thickness of the balancing plate (7) is less at the radially inner point (17) of the fins (15). This thickness is gradually increasing from inner point (17) to outer point (18) of the fins (15), thus forming a smooth, curved surface (19) on the outer face (16) of the balancing plate (7).

According to one embodiment of the invention, the location of fins (20) are alternatively placed between the locations of openings (29) as seen from the outer face (21) of the balancing plate (8). The height of fins (20) is less at the radially inner point (22) and gradually increasing radially from the inner point (22) to the outer point (23) of fins (20) forming a taper surface (24).

With the above construction of the motor (1) and its components, while the motor (1) is in operation, at least an air circulation loop (25) is formed running through the cavity (12) through the openings (14, 27 & 29) in balancing plates (7,8) and rotor stacks (5), through the gap (13) between stator stacks (4) and rotor stacks (5) and back towards the cavity (12). This loop (25) of air circulation cools the motor (1) and its all components including stator stacks (4) and rotor stacks (5).

According to another embodiment of the present invention, the outer face (16) of the balancing plate (7) may be of curved surfaces (19) having a predefined radius, for ex radius ranging from 22 to 26 mm ( for ex motor from 1.5k W to 6.5kW Rated power and rotor diameter from 80 to 125 mm). This enhances the flow of air passing over it and subsequently creation of low pressure zone and air circulation in the loop (25).

According to another embodiment of the present invention, a taper surface (24) of fins (20) is at a predefined angle perpendicular to direction of the axis of the motor shaft (26) for ex at a angle of 68 to 72 degrees perpendicular to direction of the axis of the motor shaft (26) ( for ex motor from 1.5k W to 6.5kW Rated power and rotor diameter from 80 to 125 mm). . This enhances the suction air from openings (27 & 29) and throw it towards the gap (13) between stator stacks (4) and rotor stacks (5) by creation of high pressure zone and subsequently enhance air circulation in the loop (25).
According to another embodiment of the present invention, construction (periphery or shape (28)) of the openings (14, 27& 29) is same in both the balancing plates (7,8) and rotor stacks (5). This enhances the flow of air passing through it and subsequently the air circulation in the loop (25).
According to another embodiment of the present invention, the gap (13) between stator stacks (4) and rotor stacks (5) is predefined, for ex between 0.4 to 0.5 mm
According to another embodiment of the present invention, the shape (28) of the openings (14, 27 & 29) are substantially of rhombus shape and have less width at inner side.
According to another embodiment of the present invention, air in the circulation loop (25) cools by contacting with the relatively cooler motor housing (2), as the motor housing ( 2) is at ambient temperature.

BRIEF DESCRIPTION OF DRAWINGS:
Figure 1 is a pictorial side view of an electric motor according to one embodiment of the present invention.
Figure 2 is an exploded view of an electric motor according to one embodiment of the present invention.
Figure 3 is an exploded view of a rotor of an electric motor according to one embodiment of the present invention.
Figure 4a is a perspective view of a one balancing plate according to one embodiment of the present invention.
Figure 4b is a side view and cross section view of a one balancing plate according to one embodiment of the present invention.
Figure 5a is a perspective view of another balancing plate according to one embodiment of the present invention.
Figure 5b is a side view and cross section view of another balancing plate according to one embodiment of the present invention.
Figure 6 is a perspective view of rotor of an electric motor according to one embodiment of the present invention.
Figure 7 is a cut section view of an electric motor according to one embodiment of the present invention.
Figure 8 is a pictorial side view of an electric motor showing the travel loop of air circulation according to one embodiment of the present invention.
Figure 9 and Figure 10 are pictorial view of test results of velocity measurement simulation of air circulation according to one embodiment of the present invention

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT:

Embodiments of present invention will now be explained with the help of figures herein below. All the aspects described herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope herein without departing from the spirit and scope thereof, and the present invention herein includes all such modifications.

Referring to figures 1 to 8, according to one embodiment of the present invention, an electric motor (1) comprises: a motor housing (2), a stator stacks (4), a rotor stacks (5), a motor shaft (6), a balancing plate (7), and a balancing plate (8). The stator stacks (4) are attached to motor housings (2) from their inner sides. The rotor stacks (5), the balancing plate (7), and the balancing plate (8) are mounted on the motor shaft (6) axially and clamped with the help of keyways, washers and a nut. The motor shaft (6) is centrally mounted in motor housings (2). Plurality of openings (14, 27 & 29) are provided in the balancing plate (7), the rotor stacks (5) and the balancing plate (8) respectively in the axial direction. Plurality of fins (15) are provided on the outer face (16) of the balancing plate (7) towards the radially outward side and above the openings (14). The location of fins (15) are alternately placed between the locations of openings (14) as seen from the outer face (16) of the balancing plate (7). The thickness of the balancing plate (7) is less at the radially inner point (17) of the fins (15). This thickness is gradually increases from inner point (17) to outer point (18) of the fins (15) forming a smooth, curved surface (19). The plurality of tapered fins (20) are provided on the outer face (21) of the balancing plate (8) towards the radially outward side and above the openings (29). The location of fins (20) are alternatively placed between the locations of openings (29) as seen from the outer face (21) of the balancing plate (8). The height of fins (20) is less at the radially inner point (22) and gradually increases radially from the inner point (22) to the outer point (23) of fins (20). When the motor shaft (6) is assembled in the motor housings, a cavity (12) is created between the motor housing (2) and the balancing plate (7). Similarly, a thin gap (13) is created between stator stacks (4) and rotor stacks (5) in the radial direction. Also a cavity (3) is created between the motor housing (2) and the balancing plate (8).

While the motor (1) is in operation, the motor shaft (6) starts rotating along with the rotor stacks (5), the balancing plate (7), and the balancing plate (8). A low pressure zone is created due to the rotation of the fins (15), the varying thickness of the balancing plate (7), and the smooth curved surface (19). The air in the cavity (12) is sucked into the openings (14) due to this low pressure, and the air passes through the openings (27) of the rotor stacks (4) towards the balancing plate (8). A high pressure zone is created by the rotation of the balancing plate (8) with the help of tapered fins (20), which suck air from openings (29) of the balancing plate (8) and throw it towards the gap (13) between stator stacks (4) and rotor stacks (5). This air passes through the gap (13) towards the cavity (12). This is how a circular air travel loop (25) is formed. Due to this air circulation, all components of the motor (1), especially the stator stacks (4) and rotor stacks (5) and magnets, are cooled. The air in the circulation loop (25) is cooled by contacting with the relatively cool motor housing (2) as the motor (1) is at ambient temperature.Pressure zones dependent on constructional /positional features of end plates.

According to one embodiment of the present invention, and with reference to Figures 9 and 10, test results of the velocity measurement simulation of air circulation show that there is a significant improvement in the air velocity at different points in its circulation loop, which results in faster cooling of motor components by the air circulation. This simulation is done by Computational Fluid Dynamics (CFD), a process of mathematically predicting physical fluid flow by solving the governing equations using computational power.

With above embodiments of the invention the problem mentioned earlier in the electric motor can be solved effectively.

Although the invention has been described with regard to its embodiments, specific embodiments, and various examples, which constitute the best mode presently known to the inventors, it should be understood that various changes and modifications as would be obvious to one having the ordinary skill in this art may be made without departing from the scope of the invention. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. All changes that come with meaning and range of equivalency of the claims are to be embraced within their scope.
,CLAIMS:WE Claim:
Claim 1: An electric motor comprising:
a) motor housing (2)
b) at least stator stacks (4) attached to the motor housing (2)
c) a motor shaft (6)
d) at least rotor stacks (5) axially attached to the motor shaft (6)
e) balancing plates (7,8) axially attached to the motor shaft (6) on both sides of rotor stacks (5)
f) a cavity (12) is provided between the motor housing (2) and the balancing plate (7)
g) a cavity (3) is provided between the motor housing (2) and the balancing plate (8)
Claim 2: An electric motor as claimed in claim 1 wherein;
Said balancing plates (7, 8) and rotor stacks (5) are provided with a plurality of openings (14, 29 & 27) respectively allowing air to through them,
Claim 3: An electric motor as claimed in claim 1 wherein said balancing plate (7) having a varying thickness and curved surface (19) and is provided with plurality of fins (15) to create a low pressure zone for sucking air through the cavity (12) and pass through the openings (14, 27 & 29);
Claim 4: An electric motor as claimed in claim 1 wherein;
said balancing plate (8) is provided with plurality of taper fins (20) to create a high pressure zone for sucking air from the openings (27, 29) and throwing air through the gap (13) between stator stacks (4) and rotor stacks (5) towards the cavity (12) forming a loop (25) of air circulation to cool all parts of the motor (1),

Claim 5: An electric motor as claimed in claim 1 wherein said cavity (3) is provided between motor housing (2) and the balancing plate (8).

Claim 6: An electric motor as claimed in claim 3 wherein the location of fins (15) are alternatively placed between the locations of openings (14) as seen from the outer face (16) of the balancing plate (7).

Claim 7: An electric motor as claimed in claim 3 wherein the thickness of the balancing plate (7) is less at the radially inner point (17) of the fins (15) and the thickness is gradually increasing from inner point (17) to outer point (18) of the fins (15), forming a smooth, curved surface (19) on the outer face (16) of the balancing plate (7).

Claim 8: An electric motor as claimed in claim 4 wherein location of fins (20) are alternatively placed between the locations of openings (29) as seen from the outer face (21) of the balancing plate (8).
Claim 9: An electric motor as claimed in claim 4 wherein height of fins (20) is less at the radially inner point (22) and gradually increasing radially from the inner point (22) to the outer point (23) of fins (20) forming a taper surface (24).

Claim 10: An electric motor as claimed in claim 1 the outer face (16) of the balancing plate (7) is of curved surfaces (19) having a pre-defined radius to enhance the flow of air passing over it and creating low pressure zone in the air circulation loop (25).

Claim 11: An electric motor as claimed in claim 4 wherein , a taper surface (24) of fins (20) having a pre-defined angle degrees perpendicular to direction of the axis of the motor shaft (26) enhancing the suction air from openings (27 & 29) and throwing it towards the gap (13) between stator stacks (4) and rotor stacks (5) by creation of high pressure zone.
Claim 12: An electric motor as claimed in claim 2 construction of the openings (14, 27& 29) is same in both the balancing plates (7,8) and rotor stacks (5) enhancing the flow of air passing through them.

Claim 13: An electric motor as claimed in claim 12 wherein constructional shape of the openings (14, 27 & 29) are substantially of rhombus shape and have less width at inner side.
Claim 14: An electric motor as claimed in claim 4 air in the circulation loop (25) gets cooled by contacting with the relatively cooler motor housing (2).
Claim 15: A cooling system for an electric motor comprising
a) motor housing (2)
b) at least stator stacks (4) attached to the motor housing (2)
c) a motor shaft (6)
d) at least rotor stacks (5) axially attached to the motor shaft (6)
e) balancing plates (7,8) axially attached to the motor shaft (6) on both sides of rotor stacks (5)
f) a cavity (12) is provided between the motor housing (2) and the balancing plate (7)
g) a cavity (3) is provided between the motor housing (2) and the balancing plate (8)
Claim 16: A cooling system for an electric motor as claimed in claim15 wherein the balancing plates (7, 8) and rotor stacks (5) are provided with a plurality of openings (14, 29 & 27) respectively to pass air through them; the balancing plate (7) has a varying thickness and curved surface (19) and is provided with plurality of fins (15) creating a low pressure zone for sucking air through the cavity (12) and pass through the openings (14, 27 & 29);
and wherein;
the balancing plate (8) is provided with plurality of taper fins (20) to creating a high pressure zone for sucking air from the openings (27, 29) and throwing air through the gap (13) between stator stacks (4) and rotor stacks (5) towards the cavity (12) forming a loop (25) of air circulation to cool all parts of the motor.