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 frame wrap for a motor
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Pangal Sarvesh and Bhandakkar Parag; both of Crompton Greaves Ltd, Large & Traction Machines Division, D5, 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:
This invention relates to the field of mechanical assemblies. Particularly, this invention relates to a frame wrap for a motor.
Background of the Invention:
An electric motor converts electrical energy into mechanical energy. IT contains three main components; stator, rotor, and commutator. The rotor is the non-stationary part of a rotary motor, which rotates because the wires and magnetic field of the motor are arranged so that a torque is developed about the rotor's axis. The stator is the stationary part of a rotor system. The commutator is a rotary electrical switch that periodically reverses the current direction between the rotor and the external circuit. The rotor has a fanning action.
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. General induction motors that have stator frames fabricated from mild steels have structures with straight side wraps.
The stator frames of a motor are subject to the following conditions for providing a safe and efficient housing:
1) stress levels due to the working of the motor i.e. the rotary motion of the rotor in the stator and weight of the stator and rotor;
2) excitation frequency of the rotor (in order to avoid resonance); and
3) temperature of operation of motor (due to heat dissipation).

It is important that the stator frame be robust to take care of the above-mentioned conditions. It is simultaneously important that the robustness does not result in increase in weight of the frame.
It was observed that the inclusion of several ribs and several plates in a stator frame wrap resulted in vortex formation of the (hot) air exiting out of the fanning action of the rotor. Due to a non-clear passage of air, this air moved about in the stator frame wrap resulting in an unhealthy ambient surrounding for the motor.
Prior Art:
FR2944654 discloses a Supporting frame for stator of rotating electric machine e.g. motor, has connection elements distributed around stator and extended parallel to machine axle, and plate connected to internal flanges by elements adjustable in length. There are clear possibilities of vortex formation in this structure.
US4450373 discloses an apparatus for reducing vibration in a motor of the type having a rotor and a stator, comprising a pair of rotor support members in end shields for the motor and including means to transmit forces generated by the rotor at the bearings through the end shields to reinforcing stiffening members in the motor housing which are directly connected to the motor support members. Even if stiffness is increased, the above-mentioned concerns, of the prior art, other than stiffness are not resolved, here.

Objects of the Invention:
An object of the invention is to provide a structurally stiff frame wrap for a motor.
Another object of the invention is to provide a relatively light weight stator frame.
Yet another object of the invention is to provide a stator frame adapted to absorb incumbent stress levels of the rotor and stator housed in it.
Still another object of the invention is to provide a stator frame adapted to not reach a resonating frequency of rotation of the rotor.
Another object is to increase the stiffness of the stator frame structure.
An additional object of the invention is to provide a stator frame adapted to be temperature efficient i.e. provide better heat dissipation capability.
Yet an additional object of the invention is to provide a stator frame with reduced vortex formation.
Still an additional object of the invention is to provide a thermodynamically efficient stator frame wrap.

Summary of the Invention:
According to this invention, there is provided a frame wrap for a motor, said frame wrap comprises:
a. substantially rectangular housing with pre-profiled side plates, said
pre-profiled side plated characterised by three-way side bended plates
such that there is a C-curved upper portion followed by a straight
middle portion and an inverse L-shaped bottom portion;
b. plurality of latitudinal dispersed plates across the length of said
housing; and
c. at least a longitudinal rib running across the length of said housing,
said rib joining one plate to another.
Preferably, said side plates are mild steel grade B side plates.
Typically, said latitudinal dispersed plates are holed plates to circumferentially cover a stator.
Brief Description of the Accompanying Drawings:
Figure J illustrates an isometric view of the frame wrap of the prior art.
The invention will now be described in relation to the accompanying drawings, in which:
Figure 2 illustrates an isometric view of the frame wrap;
Figure 3 illustrates a side plate of the frame wrap;

Figures 4 and 5 illustrate additional isometric view of the frame wrap of Figure 2;
Figure 6 illustrates an isolated profile view of the side plate of the frame wrap;
Figure 7 illustrates a FEA modal analysis to depict the structural stiffness of the frame wrap of Figure 2;
Figure 8 illustrates air flow pattern due to a motor placed in the frame wrap.
Detailed Description of the Accompanying Drawings:
Figure 1 illustrates an isometric view of the frame wrap (10) of the prior art.
This housing includes a substantially rectangular box with a plurality of latitudinal dispersed plates (12) across its length. These plates (12) are supported by the facilitation of many longitudinal ribs (14) running across the length joining one plate to another. The profiles of the side walls (16) are not conducive the air flow exit path from the rotor. Hence, this stator frame, for a plurality of purposes is an unfit stator wrap from thermodynamics point of view.
According to this invention, there is provided a frame wrap (100) for a motor.

Figure 2 illustrates an isometric view of the frame wrap. Figure 3 illustrates a side plate of the frame wrap. Figures 4 and 5 illustrate additional isometric view of the frame wrap of Figure 2. Figure 6 illustrates an isolated profile view of the side plates of the frame wrap.
In accordance with an embodiment of this invention, there is provided a substantially rectangular housing with pre-profiled side plates (20). The side plates (20) are profiled in a manner so as to increase the stiffness of the frame wrap (100).
These side plates (22) are welded onto the structure of the frame. The material of the side plates is mild steel grade B, according to one exemplary embodiment. The side plates' profile has a special design and is bent from a flat sheet of steel in stages to get the desired shape (as shows in Figures 3 and 6 of the accompanying drawings).
The cross section of the motor reveals its actual bent shape as shown in Figure 3 of the accompanying drawings.
In accordance with another embodiment of this invention, said side plates (20) are three-way side bended plates such that there is a C-curved upper portion (A) followed by a straight middle portion (B) and an inverse reshaped bottom portion (C) adapted to fit the new profile of the side plate as seen in Figure 6 of the accompanying drawings.

The side plates are bent in a unique way with 3 bending operations (32, 34, 36) involved to create the plate as shown in Figure 6 of the accompanying drawings. This plate is then welded on to the frame structure and becomes an integral part of the motor stator frame.
In accordance with yet another embodiment of this invention, there are provided a plurality of latitudinal dispersed plates (22) across its length. These plates (22) are supported by the facilitation of at least a longitudinal ribs (24) running across the length joining one plate to another. There is a clear reduction in the number of these plates (22) and the number of ribs (24), without compromising on stiffness.
Figure 7 illustrates a FEA modal analysis to depict the structural stiffness of the frame wrap of Figure 2. Figure 8 illustrates air flow pattern due to a motor placed in the frame wrap.
It can be seen from Figure 8, that the velocity of exiting air is not turbulent air.
According to an observed exemplary embodiment, incorporating this shape
of the stator frame gave the following advantages:
1) The stiffness of the frame increased considerably. The measure of stiffness of the frame was derived from the natural frequencies of the frame in the free-free condition. It observed an increase of 25% Hertz in the fundamental frequency which is also known as the first modal

frequency. This increased frequency of vibration is due to the shape modification that was done.
2) The shape also helped in reducing the air path bottlenecks, streamlining its path as it moves into the heat exchanger.
3) The shape made the frame stiff enough that the overall weight of the frame was reduced by around 10%. In order to provide stiffeners in the frame, the earlier design used heavy rectangle cross section of about 40x40mm, eight of them equally spaced to impart rigidity to the structure. The new design of this invention completely eliminated this requirement and hence the weight reduction.
4) The ribs in the earlier design ran along the length of the frame. The frame structure has intermediate plates in order to support the stator core. These ribs were welded throughout each of the intermediate plates. Since the 8 numbers of ribs were removed in the new stator frame, all the additional welds were avoided, number of joints was reduced and hence the stress created due to welding reduced drastically.
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 frame wrap for a motor comprising:
a. substantially rectangular housing with pre-profiled side plates, said
pre-profiled side plated characterised by three-way side bended plates
such that there is a C-curved upper portion followed by a straight
middle portion and an inverse L-shaped bottom portion;
b. plurality of latitudinal dispersed plates across the length of said
housing; and
c. at least a longitudinal rib running across the length of said housing,
said rib joining one plate to another.
2. A frame wrap as claimed in claim 1 wherein, said side plates are mild steel grade B side plates.
3. A frame wrap as claimed in claim 1 wherein, said latitudinal dispersed plates are holed plates to circumferentially cover a stator.