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 motor with shaft potential earthing assembly
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Khatua Satyaranjan, of Crompton Greaves Ltd, machine (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 motors.
Particularly, this invention relates to a motor with shaft potential earthing assembly.
BACKGROUND OF THE INVENTION:
A motor for electrical purposes, i.e. an electric motor, is a device which converts electrical energy to mechanical energy.
Figure 1 illustrates a schematic motor.
A stator and rotor (12) is located about a shaft (14) in a motor housing (16).
A drive (18) drives the motor.
An end shield (20) placed over bearing forms the lateral enclosure for the motor. The end shields are designed for fitting the bearing assembly and take care for transmitting the static and dynamic load. Depending on the design and the operating conditions, the motors are fitted with grease lubricated rolling element bearings. Reference numeral 22 refers to an end shield of the drive end.
The motor is connected to a load (24) at its drive end.
In a normal motor, two insulated electrical bushings are provided; each bushing with an inner race and an outer race. When two sides of bearings are insulated, usually an earth brush (26) is provided to short one of the

bearings. This brush will ground the shaft voltage so that no potential will appear across the load side (24).
However, when the same is applied to a hazardous condition, earth brushes cannot provide earthing as per specified electrical regulations. So, grounding should be done in such a manner that grounding of the shaft voltage should be done through some arrangement through which the risk of hazard can be eliminated completely.
OBJECTS OF THE INVENTION:
An object of the invention is to provide effective shorting / earthing of shaft potential for a motor.
Another object of the invention is to provide a relatively safer motor.
Yet another object of the invention is to provide a motor which does not transfer shaft potential to a coupled load.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a motor with shaft potential earthing assembly, said motor comprising a rotor, a shaft in a motor housing, a drive element, a load, and a drive end end-shield lateral to said motor housing, said end shield placed between said motor housing and said load, characterised in that, said assembly comprises:

a. electrical bushing with an outer bearing race and an inner bearing
race, said electrical bushing including a through slot for bolting
arrangement through outer bearing cover;
b. shorting link fitted on said bolting arrangement with respect to said
through slot;
in order to provide a path for shaft potential for said motor so that no potential appears across said load.
Typically, said outer bearing race is a static bearing race-
Typically, said outer bearing race is a static bearing race enveloped by an outermost circumferential insulating ring.
Typically, said electrical bushing is a mechanically coupled electrical busing adapted to be mechanically coupled with respect to said end shield of said motor.
Typically, said shorting link is provided between said motor end shield and said outer bearing race through a solid contact.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a schematic diagram of a motor-
The invention will now be described in relation to the accompanying drawings, in which:

Figure 2 illustrates a schematic diagram of a motor with shaft potential earthing assembly;
Figure 3 illustrates a schematic isometric view of the modified bearing assembly for mounting a shorting link for earthing shaft potential; and
Figure 4 illustrates a schematic coupling of shorting link with insulation bearing and end shield of motor.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a motor with shaft potential earthing assembly.
Figure 2 illustrates a schematic diagram of a motor with shaft potential earthing assembly.
Figure 3 illustrates a schematic isometric view of the modified bearing assembly for mounting a shorting link for earthing shaft potential.
Figure 4 illustrates a schematic coupling of shorting link with insulation bearing and end shield of motor.
The motor assembly comprising a rotor (12), shaft (14), motor housing (16), drive (18), load (24) is explained above in reference to Figure 1 of the accompanying drawings.

In accordance with an embodiment of this invention, there is provided an electrical bushing (30) (as shown in Figure 3 of the accompanying drawings) with an outer bearing race (32) and an inner bearing race (34), wherein, a through slot (36) is provided. The slot (36) provides a place where a bolt is connected through outer bearing cover (35).
The inner bearing race (34) is a moving race and the outer bearing race (32) is a static race. The slot (36) is, therefore, provided on the outer bearing race (32).
The electrical bushing (30) is adapted to be mechanically coupled with respect to an end shield of the motor. The outermost annular ring (38) is the insulating ring.
Reference numeral 33 (of Figure 4) depicts the shaft over which the insulation bearing (30) is mounted.
In accordance with another embodiment of this invention, there is provided a shorting link (40) fitted with respect to the slot (36).
The shorting link is provided between the motor end shield (22) and outer bearing race (36) (of Figure 3) through a solid contact. But the problem with the outer bearing race (30) is that it is completely insulated (38) (of Figure 3). So, a small portion on the bearing race side is removed (slot - 36 of Figure 3) and the shorting link (40) is connected, therethrough. This ensures a solid contact and can be used for a motor.

Therefore, a path for shaft potential in case of a (flame proof) motor is provided. And no potential will appear across the load.
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 motor with shaft potential earthing assembly said motor comprising a rotor, a shaft in a motor housing, a drive element, a load, and a drive end end-shield lateral to said motor housing, said end shield placed between said motor housing and said load, characterised in that, said assembly comprising:
a. electrical bushing with an outer bearing race and an inner bearing
race, said electrical bushing including a through slot for bolting
arrangement through outer bearing cover;
b. shorting link fitted on said bolting arrangement with respect to said
through slot,
in order to provide a path for shaft potential for said motor so that no potential appears across said load.
2. A motor as claimed in claim 1 wherein, said outer bearing race is a static bearing race.
3. A motor as claimed in claim 1 wherein, said outer bearing race is a static bearing race enveloped by an outermost circumferential insulating ring.
4. A motor as claimed in claim 1 wherein, said electrical bushing is a mechanically coupled electrical busing adapted to be mechanically coupled with respect to said end shield of said motor.

5. A motor as claimed in claim 1 wherein, said shorting link is provided between said motor end shield and said outer bearing race through a solid contact.