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 fan cover for Totally Enclosed, Fan Cooled (TEFC) motors, and an improved motor thereof.
APPLICANT:
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Gorre Uday Kumar and Jain Prateek Kumar; both of Crompton Greaves Limited Analytics Centre, C G Global R&D Centre, Bhaskara Building, Crompton Greaves ltd, Kanjurmarg (E), Mumbai - 400042, Maharashtra, 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:
This invention relates to the field of motors and cooling mechanisms for motors.
Particularly, this invention relates to Totally Enclosed, Fan Cooled (TEFC) motors and fan covers for TEFC motors.
More particularly, this invention relates to a fan cover for Totally Enclosed, Fan Cooled (TEFC) motors, and an improved motor thereof.
BACKGROUND OF THE INVENTION:
A motor is an electrical component or device or apparatus which converts electrical energy into mechanical energy.
Electricity, flowing through motor windings, develops heat due to the resistance of the windings. This heat is developed continuously and therefore the heat must also be removed / dissipated continuously or else the temperature of the windings would rise until the winding insulation is burned out.
Hence, the motor is constructed with a small fan on the rear shaft of the motor, usually covered by a housing. This fan draws air over the motor body, removing excess heat and cooling the motor.
Totally Enclosed, Fan Cooled (TEFC) motors are enclosure motors. This ordinarily means that the motor is dust tight, and has a moderate water seal as well. TEFC motors have an externally mounted fan covered by a shroud blowing air across the surface of the motor enclosure. Heat developed in the windings moves by convection outward through the motor case then into the air moving along the

surface of the motor case. The motor case is a heat sink drawing heat from the motor interior to the outside. TEFC motors may have fins on the motor case enhancing this heat transfer into the air.
According to the prior art, the TEFC motor includes a fan cover which allows for circular and conical air entry and exit. This design / geometry provided substantially less and non uniform air distribution over the frame; hence less heat transfer from the frame occurs. Also the direction of air flow is not guided so as to route movement over a maximized surface area of the motor housing.
This lack of adequate cooling necessitates higher surface area and outer diameter for winding and hence results in more stamping material. To reduce the losses, the amount of conductor material also needs to be increased. The core length also increases.
OBJECTS OF THE INVENTION:
An object of the invention is to provide improved cooling for a TEFC motor or for any appliance or electrical component which require forced cooling.
Another object of the invention is to provide a fan cover to guide air flow across a TEFC motor.
Yet another object of the invention is to provide a flow path for air to be guided over the motor housing.
Still another object of the invention is to provide relatively higher heat transfer coefficients by increasing velocity of air using trapezoidal vanes for motor cooling.

An additional object of the invention is to provide relatively higher cooling capacity for motor without altering fan size or fan output capacity.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a fan-cover for an externally cooled motor, said fan cover being a substantially cap shaped assembly comprises an annular rim member with one end of said rim member being closed by an end cover, said end cover including slots which facilitate entry of air from the atmosphere into said fan cover, characterised in that, said rim member further comprises a plurality of radially dispersed guide vanes which are aligned substantially parallel to a central axis of said rim member and are spaced apart from each other.
According to this invention, there is also provided an improved motor with a fan-cover, mounted as a shroud over said motor at its one end such that there is a gap between the rim circumference and the motor circumference, for externally cooling said motor, said motor comprises:
a) fan cover being a substantially cap shaped assembly comprising an annular rim member with one end of said rim member being closed by an end cover, said end cover including slots which facilitate entry of air from the atmosphere into said fan cover, characterised in that, said rim member further comprises a plurality of radially dispersed guide vanes which are aligned substantially parallel to a central axis of said rim member and are spaced apart from each other;
b) fan located in said fan-cover.

Preferably, each of said guide vanes is a tapering guide vane with respect to its tapering breadth from said end cover to an open end of said rim member.
Preferably, each of said guide vanes is a trapezoidal guide vane with respect to its tapering breadth from said end cover to an open end of said rim member.
Alternatively, each of said guide vanes is a linear guide vane with respect to its length from said end cover to an open end of said rim member.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in
which:
Figure 1 illustrates a cut-section schematic view of a motor;
Figure 2 illustrates an isometric view of a motor, with fan cover, according to the prior art; and
Figure 3 illustrates a schematic isometric view of a fan cover.
Figure 4 illustrates a schematic isometric view of a fan cover, with trapezoidal guide vanes, for a TEFC motor;
Figure 5 illustrates a schematic isometric view of a motor with a fan cover of Figure 4;

Figure 6 illustrates a schematic isometric view of a fan cover, with straight guide vanes, for a TEFC motor;
Figure 7 illustrates a schematic isometric view of a motor with a fan cover of Figure 6;
Figure 8 illustrates a CFD analysis of a motor with a fan cover of the prior art; and
Figure 9 illustrates a CFD analysis of a motor with a fan cover, having trapezoidal vanes, in accordance with this invention.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a fan cover for Totally Enclosed, Fan Cooled (TEFC) motors, and an improved motor thereof.
Figure 1 illustrates a cut-section schematic view of a motor (50).
Reference numeral 02 refers to stator windings. Reference numeral 04 refers to fan
cover of the prior art.
Figure 2 illustrates an isometric view of a motor (50), with fan cover (04), according to the prior art.
Figure 3 illustrates a schematic isometric view of a fan cover (04). This fan cover includes slots (16) for air entry.
Figure 4 illustrates a schematic isometric view of a fan cover, with trapezoidal guide vanes, for a TEFC motor.

In accordance with an embodiment of this invention, there is provided a fan cover (100) which is substantially a cylindrical cap shaped assembly. It includes an annular rim (12) with one end of the rim being closed by an end cover (14). A fan is located in this fan cover. The end cover includes slots (16) which facilitate entry of air from the atmosphere into the fan cover.
The fan cover (100) is a shroud over the motor (150) from one end such that there is a gap (30) between the rim circumference and the motor circumference.
Heat produced inside motors is removed by circulating air over it. This air passes through the frame / shell of the motor. An external fan churns out this air. This air is guided over the frame by a fan cover (100, 200).
In accordance with an embodiment of this invention, there are provided a plurality of radially dispersed guide vanes which are aligned substantially parallel to a central axis and are spaced apart from each other.
In accordance with a first embodiment of this invention, each guide vane is a tapering guide vane (22) with respect to its tapering breadth from the end cover (14) to the open end. This tapering shape is a substantially trapezoidal shape for each guide vane (22). This tapering shape facilitates the guidance of air away from the end cover to the opening. Consecutive tapered guide vanes are spaced apart from each other. The guide vanes (22) cause some turbulence which is effective in the cooling process. The presence of guide vanes (22) and the space between them ensures that the air from the fan cover (100) is passed in a manner such that it has relatively greater contact with the motor body, thereby causing heat transfer from the motor to the air and resulting in motor cooling.

Figure 5 illustrates a schematic isometric view of a motor (150) with a fan cover of Figure 4.
If a fan cover with guide vanes is not used, the air disperses away from the motor body after only a minimum contact with a portion of the motor body which is close to the fan cover. The guide vanes proposed in the fan cover guide the air effectively over the frame for TEFC motor.
This arrangement and fan cover guides the flow, increases velocity of air and enhances turbulence. It increases pressure drop and heat transfer. This allows more turbulence for same airflow, thereby cooling the winding more effectively. This can reduce frame or winding size, fan outer diameter, fan power required and conductor size. This can reduce the cost of the motor.
Figure 6 illustrates a schematic isometric view of a fan cover, with straight guide vanes, for a TEFC motor.
In accordance with a second embodiment of this invention, each guide vane is a linear guide vane (42) with respect to its length from the end cover (14) to the open end. This linear shape, too, facilitates the guidance of air away from the end cover to the opening. Consecutive guide vanes are spaced apart from each other. The guide vanes (42) cause some turbulence which is effective in the cooling process. The presence of guide vanes (42) and the space between them ensures that the air from the fan cover (200) is passed in a manner such that it has relatively greater contact with the motor body, thereby causing heat transfer from the motor to the air and resulting in motor cooling.

Figure 7 illustrates a schematic isometric view of a motor (250) with a fan cover of Figure 6.
Figure 8 illustrates a CFD analysis of a motor with a fan cover (04) of the prior art. Figure 9 illustrates a CFD analysis of a motor with a fan cover (100), having trapezoidal vanes, in accordance with this invention.
In Figure 8, the lines show the relatively lesser amount of contact of air flowing from the fan cover and around the motor body (50) which needs to be cooled.
In Figure 9, the lines show increase in contact of air passing through the fan cover which flows about the motor body, thereby resulting in increased cooling.
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 fan-cover for an externally cooled motor, said fan cover being a substantially cap shaped assembly comprising an annular rim member with one end of said rim member being closed by an end cover, said end cover including slots which facilitate entry of air from the atmosphere into said fan cover, characterised in that, said rim member further comprising a plurality of radially dispersed guide vanes which are aligned substantially parallel to a central axis of said rim member and are spaced apart from each other.
2. A fan-cover as claimed in claim 1 wherein, each of said guide vanes is a tapering guide vane with respect to its tapering breadth from said end cover to an open end of said rim member.
3. A fan-cover as claimed in claim 1 wherein, each of said guide vanes is a trapezoidal guide vane with respect to its tapering breadth from said end cover to an open end of said rim member.
4. A fan-cover as claimed in claim 1 wherein, each of said guide vanes is a linear guide vane with respect to its length from said end cover to an open end of said rim member.
5. An improved motor with a fan-cover, mounted as a shroud over said motor at its one end such that there is a gap between the rim circumference and the motor circumference, for externally cooling said motor, said motor comprising: a) fan cover being a substantially cap shaped assembly comprising an annular
rim member with one end of said rim member being closed by an end cover,

said end cover including slots which facilitate entry of air from the atmosphere into said fan cover, characterised in that, said rim member further comprising a plurality of radially dispersed guide vanes which are aligned substantially parallel to a central axis of said rim member and are spaced apart from each other; b) fan located in said fan-cover.
6. An improved motor as claimed in claim 3 wherein, each of said guide vanes is a tapering guide vane with respect to its tapering breadth from said end cover to an open end of said rim member.
7. An improved motor as claimed in claim 3 wherein, each of said guide vanes is a trapezoidal guide vane with respect to its tapering breadth from said end cover to an open end of said rim member.
8. An improved motor as claimed in claim 3 wherein, each of said guide vanes is a linear guide vane with respect to its length from said end cover to an open end of said rim member.