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
A vacuum impregnation plant for simultaneously impregnating stator and rotor
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai
400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Saxena Shailesh of Crompton Greaves Ltd., Machines (M7) Division, D-5 Industrial Area, MPAKVN, Mandideep - 462046, Madhya Pradesh, India; an Indian National.
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
This invention relates to the field of mechanical engineering and mechanical assemblies.
Particularly, this invention relates to motors and impregnation plants for motors.
Specifically, this invention relates to a vacuum impregnation plant for simultaneously impregnating stator and rotor in order to reduce requirement of resin for impregnation, volume of air in vacuum and pressure cycle.
BACKGROUND OF THE INVENTION
A motor is an electromechanical assembly which comprises stator and rotor. While the stator is the stationary part of a rotor motor system, the rotor is the non-stationary part of a rotary motor.
An induction motor or asynchronous motor is a type of alternating current motor where power is supplied to the rotor by means of electromagnetic induction. In an induction motor, a rotor core is built by placing stampings over one another. A stamping is typically a lamination sheet with a centre hole. Coils / windings made of copper and covered with a mica tape for insulation is been inserted in rotor and stator for electromagnetic phenomenon.
Windings / coils in the electric motor plays an important role in the performance of the motor. It is essential for better functioning of motor to have windings properly wound and baked in an oven.

Certain motors have the windings protected by epoxy resin or varnish. By impregnating the motor stator (windings) and motor rotor (windings) with epoxy under a vacuum, one can replace air spaces within the windings with epoxy, thus sealing the windings and helping to prevent the possible formation of corona and absorption of dirt or water. This produces motors more suited to damp or dirty environments.
The entire winding along with its shell is dipped in a tank containing the varnish. The varnish, therefore, coats the winding, and also coats the shell from outside.
After placing the coil in rotor / stator, the process of vacuum pressure impregnation (in a vacuum impregnation plant) is performed to extract the moisture trapped in the voids of insulation and to protect it from getting effected from moisture further in entire lifecycle of the product. This vacuum impregnation process is very critical as these are high tension electrical machines and any kind of leakage in current can cause damage to the product or user.
In this process the stator or rotor is kept inside a closed chamber, and vacuum is created inside the chamber. Then, after achieving the vacuum level, as desired, resin is allowed to enter the chamber till it covers entire job. The vacuum is braked passing compressed air till the pressure in the impregnating tank reaches minimum 4 bar and maximum 5 bar.
For this process the dimension of the impregnation vessel is decided as per the maximum dimension of the rotor / stator.
There is a need for a better impregnation or coating system.

According to an example of typical design and dimensions, Table 1 below illustrates dimensions of rotor and stator in terms of length and diameter. 'Vessel' is the tank of the vacuum impregnation plant in which the rotor or stator is dipped. Total Volume required for vessel is 38.86 Cu M.

Rotor Stator Vessel
Length 5500mm 2500mm 5500mm
Diameter 1600mm 2500mm 3000mm
Volume 38.86 Cu M
Table 1
There is a need for a new vessel and a new vacuum impregnation plant in order to reduce the volume of resin and air, both in order to:
a. reduce time required for extraction of air;
b. Reduce quantity of air extraction to Vacuum vessel; and
c. Reduce quantity of air for pressurizing vessel.
According to the non-limiting typical exemplary embodiment, discussed above, the time required for extraction of air at lbar to vacuum of O.lmbar for the process is approximately 3hr, and the time required to achieve pressure of 5bar for pressure cycle is lhr. And the whole process is to be repeated twice (one time for stator and one time for rotor).
Further, as the rating and make of the motor changes, the size of the motor, the rotor, and the stator size, thereby, change too. Thus, the requirement of resin and

air changes, too. The above calculation is done for specific size and as the size of stator or rotor reduces in the same tank, the time and volume increase.
Hence, there is a need for new vacuum impregnation plant with vessel thereof.
PRIOR ART
The prior art document JP1268444A discloses the concept of reducing quantity of varnish in impregnating machine coil. However it involves a complex design which uses spherical spacers to reduce the space/gap in a vessel here.
There is a need for a vessel which involves combined impregnation of stator and rotor in a single vessel.
OBJECTS OF THE INVENTION
An object of the invention is to provide a vacuum impregnation plant with a vessel in order to reduce the volume of resin.
Another object of the invention is to provide a vacuum impregnation plant with a vessel in order to reduce the volume of air.
Yet another object of the invention is to provide a vacuum impregnation plant with a vessel in order to reduce pressure involved in vacuuming.
Still another object of the invention is to reduce the cycle time for the process of drawing vacuum and exerting pressure.

An additional object of the invention is to reduce the size of storage tank for resin.
An additional object of the invention is to provide flexibility of accommodating rotor as well as stator, both, in a single vessel at the same time to avoid multiple operation of vacuum impregnation plant for same motor.
SUMMARY OF THE INVENTION
According to this invention, there is provided a vacuum impregnation plant for
simultaneously impregnating stator and rotor, said rotor having extending shafts
with an operative upwardly extending shaft and an operatively downwardly
extending shaft, said rotor adapted to be ensconced within said stator, said plant
comprises:
i. a vessel with a first drum / cylinder being an upper drum / cylinder of a first
diameter; ii. said vessel with a second drum / cylinder being a lower drum / cylinder of a second diameter, said second diameter being relatively lesser than said first diameter, said second drum extending in an operative downward direction from said first drum, thereby allowing, both, rotor and shaft, to be simultaneously immersed in said medium for impregnation.
Typically, said vessel is a substantially T-shaped drum / cylinder.
Typically, said vessel comprises a first drum / cylinder of pre-defined dimensions adapted to fully immerse a stator and further adapted to partially immerse a rotor.
Typically, said vessel comprises a second drum / cylinder of pre-defined

dimensions adapted to receive said operative downwardly extending arm of said rotor.
Typically, said vessel comprises an opening at junction of said first drum / cylinder and said second drum / cylinder.
Typically, said vessel comprises filling means to fill medium of impregnation up to a level where said stator height ends such that said operative upwardly extending shaft of said rotor can be isolated from the impregnating resin.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure la illustrates a vessel used in a vacuum impregnation plant, which vessel houses a stator; and
Figure lb illustrates a vessel used in a vacuum impregnation plant, which vessel houses a rotor.
The invention will now be described in relation to the accompanying drawings, in which:
Figure 2 illustrates a schematic of a vessel used in the vacuum impregnation plant, of this invention, for simultaneously dipping stator and rotor;
Figure 3 illustrates a three dimensional schematic view of the vessel of Figure 2; and

Figure 4 illustrates a three dimensional cut-section schematic view of the vessel of Figure 2.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure la illustrates a vessel (12) used in a vacuum impregnation plant, which vessel houses a stator (S).
Figure lb illustrates a vessel (12) used in a vacuum impregnation plant, which vessel houses a rotor (R).
A drum / cylinder can be seen which constitutes the vessel. The vessel is adapted in dimensions and design to envelope a stator or a rotor. Prior art involved using this vessel, firstly, for use with stator. Additionally, prior art involved using the same vessel, secondly, for use with rotor. The stator is kept at the bottom for full immersion in the resin. Volume using prior art vessel is more - volume of resin requirement is more. Rotor has extended shafts (Rl, R2) which do not require impregnation with resin - hence, such volume is unnecessary.
According to this invention, there is provided a vacuum impregnation plant for simultaneously impregnating stator and rotor.
Figure 2 illustrates a schematic of a vessel used in the vacuum impregnation plant, of this invention, for simultaneously dipping stator and rotor.
Figure 3 illustrates a three dimensional schematic view of the vessel of Figure 2.

Figure 4 illustrates a three dimensional cut-section schematic view of the vessel of Figure 2.
In accordance with an embodiment of this invention, there is provided a substantially T-shaped drum / cylinder. This is the vessel in which equipment to be coated are placed. This vessel comprises a first drum / cylinder (22) which is the upper drum / cylinder of a first diameter. This vessel further comprises a second drum / cylinder (24) which is the lower drum / cylinder of a second diameter. The second diameter is relatively lesser than the first diameter. The second drum extends in an operative downward direction from the first drum. There is an opening at the junction of the first drum / cylinder and the second drum / cylinder.
The first drum / cylinder (22) is adapted to hold a stator. The dimensions are defined such that the stator can be fully immersed in the first drum / cylinder. Moreover, a rotor is located within the stator. This location of rotor is such that an operative upwardly extending shaft (Rl) is in the first drum / cylinder, itself, while the operative downwardly extending shaft (R2) is in the second drum / cylinder. The medium of coating is to be filled (by filling means), then, up to a level where the stator height ends as the rotor is ensconced within the stator. The operative downwardly extending shaft (R2) of the rotor can be isolated from the impregnating resin.
Hence, both, rotor and shaft, can simultaneously be immersed in the resin for impregnation, because of the T-shaped cylinder design which facilitates isolation of lower shaft in the downward extension of the T-shaped design. Resin shall be filled only to a height such that stator and rotor are immersed and upper shaft of rotor is isolated.

According to a non-limiting exemplary embodiment, a prior art vessel is compared with a vessel of this invention, in Table 2, below:

Conventional Design Proposed design
Total Volume 38.86 26.30
Resin requirement for VACUUM IMPREGNATION PLANT of Stator in Lt. 16970.97 16970.97
Resin requirement for VACUUM IMPREGNATION PLANT of Rotor in Lt. 10935.74 2904.72
Air Requirement for VACUUM IMPREGNATION PLANT of Stator CuM 26.38 8.72
Air requirement for VACUUM IMPREGNATION PLANT of Rotor CuM 26.38 20.63
Table 2
It is observed and inferred, from Table 2, above, that the total volume of the vessel has reduced from 38.86 CuM to 26.30 CuM in the current vessel. Further, resin requirement has reduced from 16970.97 Lt plus 10935.74 Lt. to 16970.97 Lt. plus 2904.72 Lt. Still further, air requirement, for stator, has reduced from 26.38 CuM to 8.72 CuM and air requirement, for rotor, has reduced from 26.38 CuM to 20.63 CuM. This results in cost reduction. Also, Volumetric efficiency is improved by 30%
The Technical Advancement of this invention lies in provisioning of a design which results in lesser material requirement and increases throughput. Further, the

technical advancement lies in provisioning a common vessel for both stator and rotor. This invention also provided Economic Significance which contributes to Inventive Step.
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. A vacuum impregnation plant tor simultaneously impregnating stator and
rotor, said rotor having extending shafts with an operative upwardly extending
shaft and an operatively downwardly extending shaft, said rotor adapted to be
ensconced within said stator, said plant comprising:
i. a vessel with a first drum / cylinder being an upper drum / cylinder of a
first diameter; ii. said vessel with a second drum / cylinder being a lower drum / cylinder of a second diameter, said second diameter being relatively lesser than said first diameter, said second drum extending in an operative downward direction from said first drum, thereby allowing, both, rotor and shaft, to be simultaneously immersed in said medium for impregnation.
2. The vacuum impregnation plant as claimed in claim 1 wherein, said vessel is a substantially T-shaped drum / cylinder.
3. The vacuum impregnation plant as claimed in claim 1 wherein, said vessel comprising a first drum / cylinder of pre-defined dimensions adapted to fully immerse a stator and further adapted to partially immerse a rotor.
4. The vacuum impregnation plant as claimed in claim 1 wherein, said vessel comprising a second drum / cylinder of pre-defined dimensions adapted to receive said operative downwardly extending arm of said rotor.
5. The vacuum impregnation plant as claimed in claim 1 wherein, said vessel

comprising an opening at junction of said first drum / cylinder and said second drum / cylinder.
6. The vacuum impregnation plant as claimed in claim 1 wherein, said vessel comprising filling means to fill medium of impregnation up to a level where said stator height ends such that said operative upwardly extending shaft of said rotor can be isolated from the impregnating resin.