FIELD OF THE INVENTION:

The present invention generally relates to the cooling methods of rotating Electrical Machines. Particularly relates to the liquid cooled Machines. More particularly relates to the liquid cooling methodology developed for the Stator frame of rotating Electrical Machines.
BACKGROUND OF THE INVENTION:
Electrical Machines generate heat during operation as a result of both electrical and mechanical losses and are to be cooled in order to ensure efficient operation of the machine. An excessively high machine temperature may result in damage to the stator winding insulation. Therefore, the Electrical Machines are designed with internal and external cooling circuits, conventionally with the air. Forced cooling is also done externally for efficient cooling.
In an embodiment of the conventional system, the rotating electric machines generally have an enclosure or housing which include a Stator frame and End Shields. The heat generated during the operation of the Machine, as a result of both electrical and mechanical losses, will flow from the sources to the surrounding parts. Electrical losses due to copper winding present in the slots of stator core contribute to major portion of heat generated. This heat will flow from the slots to core and further to the Stator frame either through conduction or convection. The heat thus generated must be cooled in order to obtain desired and efficient operation of the machine. An excessively high temperature may result in failure or damage to stator winding insulation. This will reduce the operating life of Machine and demands for maintenance at regular intervals. Efficient cooling or extraction of heat will result in machines delivering designed power, reliable operation and further in offering high power density machines, which are of high demand in the markets.
In another embodiment of the conventional system, the Electrical Machines are generally designed with internal and external air cooling circuits. Forced cooling is also done externally for efficient cooling. Apart from these cooling types, the heat is also extracted from the stator frame through fluids, mostly water and ethylene glycol. The liquid is circulated in the stator frame. The heat transfer coefficient using liquid is

generally much higher, or better, than the heat transfer coefficient with air. Therefore, in a liquid cooled machine, the overall cooling is improved and better than air cooled machine of same rating. However, the design and incorporation of cooling circuit/path in the Electrical Machine is critical as coolant conduit/circuit should be compatible for manufacture and leak proof during operation withstanding the mechanical stresses/forces.
In patent number US20080223557A1, an improved Liquid cooling system for an Electrical Machine which overcomes the problems in conventional cooling jacket methodology is disclosed. The Liquid cooling system comprises of a leak free cavity (defined as cooling jacket) made by affixing top cover(s) to stator frame. These top covers are defined as forward cover flange and aft cover flange that are affixed from each side to the frame. The cooling jacket/cavity has at least one protrusion extending into it either from the inner surface of covers or from outer surface of frame. The protrusions are in circumferential direction and may be arranged in rows in axial direction between the covers. Further, the protrusions extend alternately from forward cover flange and aft cover flange into the cavity from both sides such that a labyrinthine flow path is established in for the cooling fluid.
In patent number US3597645A, a Liquid cooling system particularly for stacks of stator laminations of electrical machinery such as Turbo-Generators is disclosed. The Cooling system comprises of the Liquid chamber sections positioned at axial ends of Stator stacks or distributed over the entire axial length of the stack of stator laminations. These chambers may either completely cool the stack of laminations or at least cool the areas of the teeth.
In patent number US20110221287A1, a Stator section for an axial flux electric machine with liquid cooling system, where the invention is related with providing Liquid cooling system to stator section such that cooling especially to Electrical conductor coils (electrical conductor wound to form coil around toroidal core) is achieved. The Liquid cooling system of stator section comprises of plurality of cooling duct sections through which coolant flows and more particularly these cooling duct sections are in contact with coils separated with Electrical Insulating material in between. The cooling duct sections are in tubular form with circular, ellipsoidal, polygonal etc., and each cooling duct section

consist of a bundle of adjacent tubular sub-elements. Further, the cooling duct sections are connected to each other hydraulically in parallel or in series.
Hence, there is a need of a Liquid cooled Stator frame with a novel cooling conduit/circuit to overcome the above mentioned problems of the conventional liquid cooling systems. Also another need in a liquid cooled Machine is the internal and/or external fan that can be eliminated which facilitates in reducing noise and fan losses.
OBJECTS OF THE INVENTION:
Considering the above criteria, following analysis have been envisaged to determine the objective of invention:
It is therefore the primary object of the present invention is to provide a Liquid cooled Stator frame for Electrical Machines to remove/extract the heat generated inside the Machine effectively.
Another object of the present invention is to provide a cooling conduit/circuit for the Liquid cooled Stator frame that have less coolant pressure drop and maintain less temperature gradient throughout the stator periphery.
Still another object of the present invention is to develop a Liquid cooled Stator frame, which will have coolant inlet and outlet ports on the same side at Non-Drive End of the Electrical Machine.
Yet another object of the present invention is to develop a Liquid cooled Stator frame, which is less susceptible to coolant leaks and withstanding mechanical stresses/forces during operation.
These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION:
One or more drawbacks of conventional and prior art systems for liquid cooling system for a stator frame in a rotating electrical machine which results in ineffective cooling of stator sections are overcome, and additional advantages are provided through a novel cooling conduit/circuit as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.
In an embodiment, the present invention relates to the cooling of rotating Electrical Machines, specifically Liquid cooling methodology developed for the Stator frame. With effective cooling or heat extraction from the Electrical Machine, the machine becomes more power dense. As the heat from the source conducts mainly to the Stator frame, the cooling is limited only to the Stator frame. Being liquid cooled, the Stator frame is designed with built-in multiple (six) cooling segments distributed circumferentially and independently at equidistant for coolant flow. These cooling segments are present axially for partial length of the Stator frame. Every cooling segment is designed with multiple (eight) metal projections into it called fins and sub-divided into two segments. Based on the machine dimensions, these cooling segments can be at least six or less in number and same principle can be incorporated even with the number of metal projections.
In an embodiment of the present invention, the Stator frame is designed with built-in multiple headers positioned at both ends of the cooling segments for coolant flow from one segment to the other. Guides were inserted at selected locations in the headers for maintaining flow in the entire cooling segment area. The headers are designed and positioned in line with the cooling segments such that a series conduit is formed in the Stator frame and also making the coolant entry and exit on one side of the Stator frame. The first and the last cooling segments are provided with the ports serving as entry and exit for the coolant. The inlet and outlet are positioned at the headers location.
In another embodiment of the present invention, the shape and size of the cooling segments, headers and profile of fins and guides are designed to achieve uniform peripheral heat extraction from inside the Machine resulting in less temperature gradient

throughout the stator periphery, less pressure drop in the conduit/circuit and further in a leak proof Liquid cooled frame withstanding the mechanical stresses.
With the intention of providing an effective cooling by developing a Liquid cooled Stator frame having less coolant pressure drop and maintain less temperature gradient throughout the stator periphery, the present invention is advantageous.
Various objects, features, aspects, and advantages of the inventive subject matter will
become more apparent from the following detailed description of preferred
embodiments, along with the accompanying drawing figures in which like numerals
represent like components.
It is to be understood that the aspects and embodiments of the disclosure described
above may be used in any combination with each other. Several of the aspects and
embodiments may be combined to form a further embodiment of the disclosure.
The foregoing summary is illustrative only and is not intended to be in any way limiting.
In addition to the illustrative aspects, embodiments, and features described above,
further aspects, embodiments, and features will become apparent by reference to the
drawings and the following detailed description.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of apparatus that are consistent with the subject matter as claimed herein, wherein:
Figure 1 illustrates the side and front elevation views of Rotating Electrical Machine with Liquid cooled Stator frame 100 according to an embodiment of the present invention.
Figure 2 (a) illustrates a long sectional view along the axial length of Liquid cooled Stator frame 100 of Electrical Machine as shown in Figure 1 according to an embodiment of the present invention.

Figure 2 (b) illustrates a cross-sectional view of Liquid cooled Stator frame 100 of Electrical Machine shown in Figure 1 at centre (AA) according to an embodiment of the present invention.
Figure 2 (c) illustrates a cross-sectional view of Liquid cooled Stator frame 100 of Electrical Machine shown in Figure 1 at coolant entry side (BB) according to an embodiment of the present invention.
Figure 2 (d) illustrates a cross-sectional view of Liquid cooled Stator frame 100 of Electrical Machine shown in Figure 1 at coolant non-entry side (CC) according to an embodiment of the present invention.
Figure 3 (a) and (b) illustrates isometric views of the complete cooling conduit of Liquid cooled Stator frame of Electrical machine shown in Figure 1 with all cooling segments in series connection according to an embodiment of the present invention.
The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION:
While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
The drawings illustrate only those specific details that are pertinent to understand the embodiments of the present disclosure, so as not to obscure the disclosure with details that will be clear to those of ordinary skill in the art having benefit of the description herein.

In an embodiment of the Liquid cooled Stator frame according to figure 1, the Liquid cooled Stator frame (100) is assembled in the Rotating Electrical Machine with End covers or shields (101 and 102) and rotating shaft (103). The said Liquid cooled Stator frame (100) is developed with coolant ports for coolant entry (104) and coolant exit (105). A terminal box (106) is fitted securely to the outer surface of the Liquid cooled Stator frame (100) and winding terminal leads (not shown in Figure) are brought out from inside to the terminal box (106) through openings (107). The terminal box (106) further includes openings (108) for connecting power cables and sensor leads (not shown in Figure).
In an embodiment of the Liquid cooled Stator frame according to figure 2 (a), the Liquid cooled Stator frame (100) is a substantially cylindrical shaped body with hermetically built-in cooling conduit/circuit (200) between outer surface (201) and inner surface (202) and cooling is only for partial length of the frame.
In an embodiment of the Liquid cooled Stator frame according to figure 2 (b), 2 (c) and 2 (d), the built-in cooling conduit/circuit (200) consists of cooling segments (203 to 208) with headers ((209 to 215) of (Figure 2(c) and 2(d))) positioned at both ends of every cooling segment. The cooling conduit/circuit (200) has built-in multiple six cooling segments (203 to 208) distributed circumferentially and independently at equidistant for coolant flow and are present axially for partial length of the Liquid cooled Stator frame (100). Every cooling segment (203 to 208) has multiple eight metal projections into it called fins (216). Further every cooling segment (203 to 208) is sub-divided into two segments with the dividers (217) to maintain flow throughout the segment. The first and the last cooling segments are provided with the ports, positioned at the header’s location, serve as inlet (104) and outlet (105) for the coolant.
The coolant will flow from external cooling pump system into the header (209) through the inlet (104) and further enters the cooling segment (203). Now the coolant will travel through the cooling segment (203) axially and gets collected at the header (213) positioned at other end of the cooling segment (203). The coolant will flow or guided into the adjacent cooling segment (204) through the positioned header (213). Similarly, the coolant will flow from one cooling segment to the adjacent through the headers positioned on both ends of segments. The headers are designed and positioned in line

with the cooling segments such that a series conduit is formed in the Liquid cooled Stator frame (100) and also making the coolant entry and exit on one side of the Liquid cooled Stator frame (100).
In an embodiment of the Liquid cooled Stator frame according to figure 3 (a) and (b), the complete flow of coolant in the cooling conduit (200) of said Liquid cooled Stator frame (100) of Rotating Electrical machine as shown in figure 1 is disclosed. More particularly, the series connection of said cooling segments with the aid of headers and the metallic guides (300) positioned at selected locations in the headers for maintaining flow and built-in multiple metallic projections called fins along with coolant inlet and outlet ports is also disclosed.
Therefore, as the coolant/liquid flows through the segments, the coolant/liquid takes the heat conducted inside the heat source of the Stator frame. The shape and size of the cooling segments, headers and profile of fins and guides are designed to extract heat uniformly peripherally from inside the machine which ultimately resulting in less temperature gradient throughout the stator periphery and less pressure drop in the conduit/circuit.
It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.
Further, the drawings are illustrative only but not used to limit the scope of the present subject matter. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments.

We Claim:

1. A Liquid cooled Stator frame (100) with a cooling conduit for a rotating electrical
machine comprising:
- a substantially cylindrical shaped body section having at least six hermetically in-built
10 cooling segments (203 to 208) located circumferentially and at equidistant location and
allowing flow of coolant from an external source;
- at least one in-built header (209 to 215);
- wherein said in-built cooling segments (203 to 208) and the at least one in-built header (209 to 215) positioned between an outer surface (201) and an inner surface (202) of
15 said Liquid cooled Stator frame (100); and
- wherein said in-built cooling segments (203 to 208) have at least one metal projected
fin (216) throughout the length.
2. A Liquid cooled Stator frame (100) as claimed in claim 1, wherein said headers (209 to
215) preferably positioned at both the ends of the in-built cooling segments (203 to
20 208) for guiding the axial flow of coolant from one cooling segment to the adjacent
cooling segment to form a series of cooling conduit (200).
3. A Liquid cooled Stator frame (100) as claimed in claim 1, wherein said in-built headers
(209 to 215) have at least one guide (300) positioned at desired locations for
maintaining the axial flow of coolant throughout said in-built cooling segments (203 to
25 208).
4. A Liquid cooled Stator frame (100) as claimed in claim 1, wherein said in-built cooling
segment (203 to 208) is sub-divided into at least two segments with at least one divider
(217) for maintaining the axial flow of coolant throughout said in-built cooling segments
(203 to 208).
30 5. A Liquid cooled Stator frame (100) as claimed in claim 1, wherein said Stator frame (100) comprises of at least one coolant inlet port (104) and at least one coolant outer port (105) preferably located at the first (203) and the last (208) cooling segments respectively.

5 6. A Liquid cooled Stator frame (100) as claimed in claim 1, wherein said inlet port (104) and said outlet port (105) can be located for the coolant flow of said Stator frame (100), at one of driven and non-driven end of the rotating Electrical Machine.
7. A Liquid cooled Stator frame (100) as claimed in claim 1, wherein said headers (209 to
215) desirably segmented for connecting said built-in cooling segments (203 to 208) in
10 parallel combination.
8. A Liquid cooled Stator frame (100) as claimed in claim 1, wherein said cooling conduit (200) defining at least one cooling segment (203 to 208) of said Stator frame (100).
9. A Liquid cooled Stator frame (100) as claimed in claim 1, wherein said header (209) configured to receive the coolant from an external cooling pump system through said
15 inlet (104) and wherein the coolant flowing to said cooling segment (203).