FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Improved rotor laminations and axially ventilated machines, thereof.
APPLICANT :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company.
INVENTOR (S):
Pandya Ankit and Upadhyay Amarendra; both of Crompton Greaves Limited, Machines 7 Division, D-5, Industrial Area, MPAKVN, Mandideep - 462046, Madhya Pradesh, India; both Indian Nationals.
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION:
The invention relates to the field of axially ventilated machines.
Particularly, this invention relates to the field of ventilation and cooling of axially ventilated machines.
More particularly, this invention relates to improved rotor laminations and axially ventilated machines, thereof.
BACKGROUND OF THE INVENTION:
An 'electrical rotating machine' or a 'rotating electrical machine' is any form of apparatus, equipment, or system which has a rotating member and generates, converts, transforms, or modifies electric power. These include apparatus such as a motor, generator, or synchronous converter.
Essentially all of the world's electric power is produced by rotating electrical generators, and about 70% of this energy is consumed in driving electric motors. Electric machines are electromechanical energy converters; generators convert mechanical energy into electrical energy and motors convert electrical energy into mechanical energy.
An electric machine can be constructed on the principle that a magnet will attract a piece of permeable magnetic material such as iron or magnetic steel. For example, a pole structure is shown along with a magnetic block that is allowed to rotate. The

magnetic block will experience a torque tending to rotate it counterclockwise to the vertical direction.
In these examples, if the rotor were allowed to move under the influence of the magnetic forces, it would eventually come to rest at an equilibrium position. Since most applications require continuous motion and constant torque, it is necessary to keep the angle between the rotor magnetic field and the stator magnetic field constant. Thus, in the above examples, the stator magnetic field must rotate ahead of the rotor.
Although there are many variations, the three basic machine types are synchronous, induction, and direct-current machines. These machines may be used as motors or as generators, but the basic principles of operation remain the same. The synchronous machine runs at a constant speed determined by the line frequency. There is an alternating-current winding (normally on the stator) and a direct-current winding (normally on the rotor).
The performance of an 'electrical rotating machine' or a 'rotating electrical machine' is defined by many characteristics. One such characteristic is the cooling quotient and ability of the components of the machine. The rotor temperature needs to be kept in check for such electrical rotating machines. Efficient cooling of the rotor is an imperative parameter which decides its enhanced working coefficients.
Hence, there is a need for a system and design which induces efficient and improved heat dissipating characteristics, thereby resulting in improved performance.

OBJECTS OF THE INVENTION:
An object of the invention is to provide an 'electrical rotating machine' or a 'rotating electrical machine' with improved heat absorbing or heat dissipating characteristics.
Another object of the invention is to provide an 'electrical rotating machine' or a 'rotating electrical machine' with improved heat absorbing or heat dissipating characteristics, thereby resulting in better cooling of the machine.
Yet another object of the invention is to provide enhanced cooling of axially ventilated 'electrical rotating machine' or a 'rotating electrical machine'.
Still another object of the invention is to improve the ventilation capabilities of axially ventilated 'electrical rotating machine' or a 'rotating electrical machine'.
An additional object of the invention is to increase amount of air flowing through the periphery of rotor in axially ventilated 'electrical rotating machine' or a 'rotating electrical machine'.
Yet an additional object of the invention is to reduce the amount of air that is not properly used for heat dissipation in axially ventilated 'electrical rotating machine' or a 'rotating electrical machine'.

SUMMARY OF THE INVENTION:
According to this invention, there is provided an improved rotor lamination comprises vent holes surrounding an axial hole, with a plurality of rotor laminations stacked to form a rotor, characterised in that, said vent holes are serrated vent holes, with serrations at their circumferential edges.
According to this invention, there is also provided an axially ventilated machine consisting of stacked improved rotor laminations comprises vent holes surrounding an axial hole, with a plurality of rotor laminations stacked to form a rotor, characterised in that, said vent holes are serrated vent holes, with serrations at their circumferential edges.
Typically, said serrated vent holes are partitioned vent holes, characterised in that, said partition is a radial partition to form segmented serrated vent holes.
Typically, said serrated vent holes are substantially round vent holes.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates a front view of a rotor with vents; and
Figure 2 illustrates an isometric view of a rotor with vents.

Figure 3 illustrates a front view of a lamination of a rotor with serrated vents;
Figure 4 illustrates an isomeric view of a lamination of a rotor with serrated vents; and
Figure 5 illustrates a portion of a front zoomed-in view of a lamination of a rotor with serrated vents.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided an improved rotor laminations and axially ventilated machines, thereof.
Figure 1 illustrates a front view of a rotor with vents, according to the prior art. Figure 2 illustrates an isometric view of a rotor with vents, according to the prior art.
In general, according to prior art designs and apparatus, laminations (100) which form the rotor comprise vent holes (12) surrounding an axial hole (14). The laminations are axially stacked to form the rotor (150). Hence, the vent holes (10) line up to form a through-hole in a substantially cylindrical shape.
According to the prior art design, the vent holes (12) have a uniform circular cross section a shown in Figures 1 and 2 of the accompanying drawings, through which air passes through in laminar fashion. Due to this laminar flow of air, the air particles which are at the inner periphery of the vent holes, come in direct contact with the lamination and are able to absorb maximum amount of heat, while the air

particles which are flowing near to the centre of the vent hole do not come in contact with the lamination surface and hence do not absorb heat as per the capacity. This results in non-utility of the entire capacity of flowing air to efficiently cool the laminations, and the rotor, in general. There is a need for an improved cooling system via changes in lamination design and, more specifically, in vent hole design.
Figure 3 illustrates a front view of a lamination (200) of a rotor with serrated vents.
Figure 4 illustrates an isomeric view of a lamination (200) of a rotor with serrated
vents.
Figure 5 illustrates a portion of a front zoomed-in view of a lamination (200) of a
rotor with serrated vents.
The design is composed of two phenomena juxtaposed with each other to enhance the cooling and ventilation of the axial ventilated machines.
In accordance with a first embodiment of this invention, the vent holes are serrated vent holes (52). These serrated vent holes include serrations at their circumferential edges. The vent holes, instead of being uniformly circular throughout its cross-section, have a shape similar to the shape as shown in Figures 3, 4, and 5 of the accompanying drawings. These serrations aid in converting the laminar flow of air to turbulent flow, as the air enters these serrated cylindrical conduits formed by a stack of laminations with serrated vent holes, which shall help in better heat absorption by the air particles. Also, relative increase in surface area of the inner circumferential periphery, due to the formation of serrations, results in relatively increased air contact that enters the vent holes, and results in relatively increased heat transfer.

In accordance with a second embodiment of this invention, the serrated vent holes (52) are partitioned vent holes. These partitions are referenced by numeral 54. The partition is done in such a manner so that maximum air flows though the lamination surface. The partition is shown in Figures 3, 4, and 5 of the accompanying drawings. The partition has been created so as to reduce the amount of air that is not properly used for heat dissipation i.e. the air that flows near to the centre of the vent hole. With this new design of the laminations of this invention, the amount of air flowing through the periphery will be higher as compared to the previous design and hence better heat transfer will result in better cooling of the rotor and hence, a motor.
The technical advancement lies in the provisioning of serrations in the vent holes of laminations that stack up to form rotors of axially ventilated machines. Further, the technical advancement also lies in partitioned vent holes so as to improve the ventilation capabilities.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. An improved rotor lamination comprising vent holes surrounding an axial hole, with a plurality of rotor laminations stacked to form a rotor, characterised in that, said vent holes are serrated vent holes, with serrations at their circumferential edges.
2. A lamination as claimed in claim 1 wherein, said serrated vent holes are partitioned vent holes, characterised in that, said partition is a radial partition to form segmented serrated vent holes.
3. A lamination as claimed in claim 1 wherein, said serrated vent holes are substantially round vent holes.
4. An axially ventilated machine consisting of stacked improved rotor laminations comprising vent holes surrounding an axial hole, with a plurality of rotor laminations stacked to form a rotor, characterised in that, said vent holes are serrated vent holes, with serrations at their circumferential edges.
5. An axially ventilated machine as claimed in claim 3 wherein, said serrated vent holes are partitioned vent holes, characterised in that, said partition is a radial partition to form segmented serrated vent holes.
6. An axially ventilated machine as claimed in claim 3 wherein, said serrated vent holes are substantially round vent holes,