2 FIELD OF THE INVENTION
The Invention relates to the area of a turbo-generator operated in a power plant for utility or industrial application. It describes in particular to the method chosen to improve the rotor end winding cooling, especially for refurbished old rotors.
BACKGROUND OF THE INVENTION
When a turbo-generator is in operation, heat is generated by the field and armature windings due to induced losses such as copper loss, eddy current loss, windage loss etc A cooling medium is circulated through the generator to continuously take away the heat so that machine temperature are kept below the permissible limits.
There are several cooling arrangements employed in the machine, depending on the design philosophy chosen and on other parameters such as medium of cooling, machine size, speed of rotation etc. Some of the arrangements are detailed below:
Radial fans are mounted on the generator rotor that rotates at 1500 rpm for 50 Hz machines and 1800 rpm for 60 Hz machines. Head is developed in view of the rotor rotation. The fans take in fresh air from the cool air chamber and force it to the stator end windings and after that into the warm air chamber.

3
The rotor takes in fresh air by self pumping, via axial ducts to the shaft area and force it through the rotor lamination via the air gap into the stator laminations. The self pumping is achieved in view of the rotor rotation Air is drawn at the inner radius of laminaton and forced out radially due to centrifugal action.
The outgoing air escapes form all around the periphery of the stator lamination, flows through the air/water coolers located in the foundation or machine and returns to the cold air chamber. Two pole generators:
Axial flow fans are mounted on rotor that rotates at 3000 rpm far 50Hz generators and 3600 rpm for 60 Hz generators. Cold air is drawn from cold chambers into the rotor end winding space to cool the rotor winding. Put of the cooling air flows past the individual coils for cooling the rotor end winding and then leaves the end winding space via bores in the rotor teeth at the end of the rotor body. The other portion of the cooling air flow is directed from the rotor end winding space into the slot bottom ducts from where is discharged into the air gap via a large number of radial ventilating slots in the coils and bores in the rotor wedges. Along these paths the heat of the rotor winding is directly transferred to the cooling air. Some air from the cold chambers is directed into the stator/rotor air gap via

4
the rotor retaining ring. The air then flows past the ventilating slots in the stator core into the hot chambers in the stator frame. This flow path mainly cools fee rotor retaining rings, the ends of rotor body and the ends of the stator core.
Incase of supply of an a new machine to a power plant, design of the
arrangement is as per the in manufacturers design philosophy. However, when a refurbishment of an old machine is taken up, iris necessary to go with the existing ventilation arrangement or in other words one has to go for a modified arrangement within the cons traints imposed by the machine layout. Improvement made to the it is neccessary cooling through a certain gain, as it generates additional power and this is of utmost interest to the poorer plants, when. it comes to the choice of opting for are refurbishment rotor going for a new machine.
Generator rotor that carries field winding, generates heat primarily doe to copper and windage losses. The field winding confutes of copper conductors drawn as per the ordered size and shaped as per the winding design. The winding is assembled in the rotor slots and same is protected from centrifugal forces by assessment rotor wedges in the dovetail slots raffled in the top of the

5
slot. The rotor wedges are mute out of hight strength non-magnetic and eectrkally coducting meter. Generators are designed to dissipare the heat during operation by circulating cooling medium. Heat loss is more pronounced in the rotor end winding zone. The resulting temperature rise will have a bearing on insulation system provided to winding. Unchecked temperature rise results in futher of insulation system. It is hence necessary to have an efficient ventilation arrangement that each heat from winding.
Cooling medium, either air or hydrogen, is forced on to rotor winding with the
and of moared on axans. To ventilare the end winding zone, one of the
methods chosen in modem day generates is to provide axial holes drilled in
the rotor teeth. The cooling gas, air or hydrogen, In circulation enters these
holes, travels axially to a specified distance and flows out through radial holes
drilled along the rotor. This arrangement takes care of the additional heat
dissipation requirement of the end winding zone. The existing arrangement in
Modern day generators is shown in FiglA.
However to refurbished designs, it is not always possible to drilled required of axial and radial holes on the rotor teeth, in view of the dimensional constraints, expended life of machine and induced operating stresses In such

6
cases, It is necessary to look at other alternatives to augment for the additional cooling requirements to achieve the intended higher machine output. The present Invention makes it possible to provide an additional part for gas flow.
OBJECT OF THE INVENTION:
The object of the invention is to improve the performance of a turbo-generator through improved rotor end winding cooling for refurbished old rotor
SUMMARY OF THE INVENTION:
Refer to Fig. 1A shows the disposition of axial and radial holes drilled in rotor
teeth for effecting end winding ventilation in newly designed rotors or as per
the present day stare of the art. The rotor is slotted to contain the filed
winding. These slots are shown at pos. 1 of the figure. The slot contents are
protected from centrifugal forces during generator rotation by means of
assembling wedge profiles, that are assembled in the dorvetail portion, pos.2 of
the rotor slot. The bottom of the slot is provided with ventilation slot that is
intended to carry the cooling medium. The cooling medium flows axially
along the length of the wilding and flows out through the winding. For
augmenting additional cooling requirements of the end winding more,
additional holes are drilled axially shown at 4 on the rotor tooth pos.5. The

air that enters these axial holes thrown out through the radial holes, pos, 6 drilled on the teeth When this philosophy is attempted for implementation in refurbished rotors, same is not always possible. Working stresses induced on the rotor teeth due to winding and wedge weights and due to tooth self weight will not permit provision of new holes during rotor repair during refurbishment. Fig. 1B shown to indfeaue what is possible it a refurbished rotor, if it is planned go for such axial and radial holes. In this figure the shape of the wedge and slot we different because, this design is as per a different philosophy. It cm be seen that the diameter of radial hole far cooling is very much limited. For a smaller diameter holes, the hydraxilic resistance wit also be higher. In view of this, the cooling will not be effective. To above are the above constraints, it is proposed in the present Invention to modify the rotor conductor design. Modified version of cooling is shown in f$g. 1C. The rotor is shown with conductors assembled. Adjacent conductors are separated by electrical insulation. Axial flutes are provided in each conductor through which ventilating gas either air or hydrogen. The gas flows out radially at predetermined locations, punched semicircular on the conductors. To have an effective ventilation, these semicircular openings are made on either side of the conductor alternatively. The openings in the coils in the radial direction are rectangular. These slots are made in alternative conductors

8
as shown in the figure. To facilitate flow of air radially, semi-circular holes are made in the total stack of conductors as well as rotor wedge. Air enters the rectangular opening or flutes made in the conductor, travels longitudinally for some distance and flows out radially out at selected locations. These semi-circular openings are made in the all toe conductor in the stack and the rotor wedge. This arrangement facilitates smooth flow of air and take away heat from the end zones. This Invention increases the generator fating by about 10%.
BRIEF DESCRIPTION OF THE ACCOMPAING DRAWINGS:
Fig. 1A shows the cooling arrangement in the present day stare of the art, Axial and radial holes drilled on each rotor teeth allow flow of gas through the end winding zone. Fig. IB shows the modified design as per the Invention. Fig. 1C shows the conductor disposition as per the Invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION:
The generator rotor is coded by air or hydrogen depending on the parameters such as type of cooling medium chosen, size of the machine etc .
The cooling medium drives oat the heat to the dosed or open circuit air cooling system.

9
Heat load at the end winding zone of the rotor- is more and hence it need additional cooling provision. As per the proposed invention, the rotor conductors and wedges are modified to have a direct cooling of the conductors. The gas flows axially through the paths obtained from the conductor mining at the ends and travels radially cut through rectangular canals formed in the bunch of conductors placed in the rotor slot. The Invention results In a more efficient cooling and improves the output of generator for the same size and other operating parameters being same.

We claim
1. An improved and efficient cooling system for turbo-generator used in
Power plant to remove excess heat generated in field and armature
windings daring operation due to induced losses such as copper loss,
eddy current loss, winding loss etc where cooling medium used are gas,
air or hydrogen characterized in that the rotor conductors (3) wedges (I)
and rotor tooth (5) are modfied and are of special constructions to have
a direct cooling of the conductors.
2. Cooling system as claimed in claim -1, wherein insulation (2) is
provided under the wedge (1)
3. Coding system as claimed in claim 1 or 2, wherein adjacent conductors
(3)are seperated by electrical insulation.
4. Cooling system as claimed in any of the claims 1 to 3, wherein axial
flutes/holes (4) are provided in each conductor through which
ventilating gas, either air or hydrogen passes.
5. Coding system as claimed in claim - 4 wherein the gas flows out
radially at predetermined locations through semicircular openings
6. Coding system as claimed to claim 5 wherein semi-circular openings
are made on either side of the conductor alternatively.
6.
11
7. Cooling system as claimed a any of the claims 1 to 6, wherein the ga
flows axially through the paths obtained from the conductor milling at
the ends and travels radially out through rectangular canals formed in
the bunch of the conductors placed in the rotor slot.
8. An improved and efficient cooling system for two-generator used in
Power Rant as substantially described herein with reference to the
accompanying drawings.
Refer to Fig IA shows the disposition of axial and radial holes drifted in rotor teeth for effecting end winding ventilation in newly designed rotors or as per the present day stare of the art. The rotor is slotted to contain the filed winding. These slots are shown at pos. 1 of the figure. The slot contents are protected from centrifugal forces during generator rotation by means of assembling wedge profiles, that are assembled in the dovetail portion, pos.2 of the rotor slot. The bottom of the slot is provided with ventilation slot dial is intended to carry the cooling medium. The cooling medium flows axially along the length of the winding slot and flows out through the winding. For augmenting additional cooling requirements of the end winding sane, additional holes are drilled axially, shown at 4on the rotor tooth pos.5. The

air that enters these axial holes thrown out through the radial holes, pos, 6 drilled on the teeth When this philosophy is attempted for implementation in refurbished old rotors, same is not always possible, Working stresses induced on the rotor teeth due to winding and wedge weights and due to tooth self weight will not permit provision of new holes during rotor repair during refurbishment. Fig. 1B shown to indicate what is possible it a refurbished rotor, if it is planned to go for such axial and radial holes. In this figure the shape of the wedge and slot are different because, this design is as per a different philosophy. It can be seen that the diameter of radial hole for coaling is very much limited. For a smaller diameter holes, the hydraulic resistance will also be higher. In view of this, the cooling will not be effective. To above are the above constraints, it is proposed in the present Invention to modify the rotor conductor design. Modified version of cooling in shown in fig. 1C The rotor is shown with conductors assembled. Adjacent conductors are separated by electrical insulation. Axial flutes are provided in each conductor through which ventilating gas, either air or hydrogen. The gas flows out radially at predetermined locations, punched semicircular on the conductors. To have an effective ventilation, these semicircular openings are made on either side of the conductor alternatively. The openings in the coils in the radial direction are rectangular. These slots are made in alternate conductors

as shown in the figure. To facilitate flow of air radially, semi-circular holes are made in the total stack of conductors as well as wedge. Air enters the
rectangular opening or flutes made in the conductor, travels longitudinally
for some distance and flows out radially out at selected locations. These semi-
circular openings are made in the all the conductors in the stack and the rotor wedge. This is arrangement facilitates smooth flow of air and take away heat from the end zones. This Invention increases the generator rating by about 10%.