FIELD OF INVENTION
The present invention deals with air cooled Turbo-Generators operating in a power
plant for an industrial application. In particular, the invention relates to a makeshift
turbo generator to replace the generator requiring a major repair and withdrawal.
BACKGROUND OF THE INVENTION
Turbo generators for different applications are tailor made, suiting to the foundation,
turbine that drives it, the routing of output terminals and cooling system employed. In
the event of major repair and withdrawal of a turbo generator, it is necessary to
procure a new generator, which is a long drawn process. The power plant has to wait
for as many weeks/ months till the replacement generator/ repaired generator is
brought and assembled.
Requirement for replacement generators comes principally in at least two cases:
i) replacement of generator in place of generator that had been in operation for quite a
long time and failed due to ageing of materials like insulation, unexpected ground
faults, spurt in vibrations, rotor faults or ventilation blockages leading to higher machine
temperatures or increase in vibrations etc. Further operation of the same generation is
not advisable/ possible. In that event, looking for replacement generator is time
consuming and power plant owner shall bear the cost of power non availability for a
longer duration.
ii) The other cases that requires immediate generator replacement, comes from
relatively newer power plants where generators are made to new technology. Many
innovations that were intended to reduce the generator size and cost, have in fact
resulted in frequent operational problems and generator failure.

In both the cases, repairing the generator, if feasible or replacing it with new generator
are the only two options as per prior art. Executing either of the options, however, is a
long drawn process. Any alternative that minimizes the downtime is very much
beneficial to the company.
The present invention provides a solution to meet this gap and ensures that the power
requirement is not interrupted beyond few days.
OBJECTS OF THE INVENTION
The object of the invention is to propose a universal make shift turbo generator which
acts as a stop gap arrangement to meet the urgent requirement of a power plant
experiencing a generator failure.
Another object of invention is to set in a process, where the size of the turbo generator
is made compact and the space required to position the generator in a power plant is
optimized.
Yet another object of invention is to fit in a generator in place of existing generator,
which had been in operation for quite some time and needs replacement.
A further object of the invention is to fit in a generator in place of a generator that falls
in a specified capacity range.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1:- Turbo generator in the prior art
Fig 2:- Turbo generator in the existing arrangement with various component details and
with pedestal mounted bearings

Fig 3:- Turbo generator as per invention
Fig 4:- Turbo generator with end shield mounted bearing
Fig 5:- Base frame that carries the turbo-generator
DETAILED DESCRIPTION OF THE INVENTION
Make shift generator is a stop gap arrangement to meet the urgent requirement of a
power plant which experienced a generator failure, generator being a 50hz, two pole air
cooled in the rating range 150 MVA to 25 MVA, repair of which takes a longer period.
The power equipment manufacturer will be ready to replace the failed generator with a
make shift generator, which is available as a stock. The features of the make shift
generator are such that it can replace generators of a given rating range, which as per
the invention are one variant for 60 to 100 MW rating range and one for 20 to 59 MW
rating range. The design approach shall be to make the make shift generator within
these prescribed ranges. It is necessary to meet the following requirements. The
generator is made to match with turbines of different ratings, of different makes and
are allowed to sit on the given foundation foot prints. The invention postulates a design
approach to make a common or universal generator that fits in place of generator made
of different design philosophies and coupled to the turbine. It includes the features built
in the generator construction that enables its fitment in most of the existing power
plants having the specified rating as described above. To make it fit, the make shift
generator shall take care of several interfaces which include:
1) Matching with turbine coupling
2) Matching with the existing foundation footprints with minor modifications and
foundation shall have adequate load bearing capacity to take the generator on.
3) Ensuring lateral and torsional stability of the combined rotor train,

4) Matching with the existing bus bar routing,
5) Have the ventilation requirements met with the existing cooling arrangement or
possible to have its own independent cooling circuit.
These are made possible through designing a generator with end shield mounted
bearings, top mounted coolers and reduced height of the stator feet with respect to the
machine access.
The end shield mount bearing arrangement will reduce the generator rotor length
considerably as shown in the figure 2. The objective is to save space and this save
spaced is utilized to mount a coupling between turbine and generator. Due to advances
made on materials front, especially on insulation system the generators have become
more compact. Introduction of modern software for design calculations made it possible
to predict the operating parameters like mechanical stresses, winding temperature
accurately and hence safety margins are reduced. The present day machines are
smaller in size vis a vis those supplied earlier. Hence there will be reduction in machine
sizes and this enables the designer to introduce a base frame that suits with the
foundation at the bottom and machine (stator and bearing pedestal) at the frame top.
The base frame is made novel by bringing flexibility in its construction. Channels are
placed back to back with gap in between and this gap is utilized to rout foundation bolts
or stator anchor bolts. The detailed construction is shown in Fig. 3. The channels are
welded at their extreme ends to I Beams on both side of the web. Then the channel
length can be increased or decreased by sliding on the I-beam before welding the
channels to the I-beams. The I-beam height is chosen as per the site requirement. •
Hence the base frame can accommodate generator stators of any length.
Additional stiffeners are provided to impart required rigidity before grouting the base
frame with secondary grout.

The generator stator is designed at the terminal exit such that higher space is created
at the terminal flange location and this gives us the flexibility to locate the terminals in
the stator frame and matching to the existing bus bar routing. Flexible connectors
assembled between the generator terminals and the bus bars will give the necessary
flexibility.
The common make shift generator that fits on the foundation and also matches with
the existing turbine coupling. The intermediate coupling changes from site to site and
its front coupling flange is made suiting to the turbine coupling. The rear side coupling
flange matches with the make shift generator rotor drive side coupling flange. The
length of the coupling is decided based on the distance between turbine and make shift
generator coupling flanges.
End shield are intended to shorten the generator rotor length and this length gain is
utilized to introduce an intermediate coupling. The coupling design is done on the
combined rotor train dynamics and torsional analysis.
The radial rib on the non-drive end is designed such that more space is available in the
output terminal zone. This space will give flexibility to match with the high voltage
terminals being routed beyond the generator.
The non-drive end of the shaft ends with coupling which is bolted to either a slip ring
shaft or brushless exciter shaft.

WE CLAIM
1. A universal make shift generator that replaces generator at site and needs to be
sent for serving having arrangement comprising:
and shield mounted bearings in place of pedestal mounted bearings in order to reduce
the generator rotor length;
an intermediate coupling installed in the space created by reduction in generator rotor
length between the turbine and generator to cater to the lateral and torsional analysis
requirement;
radial rib provided on the non drive and to create more space in the output terminal
zone;
the make shift generator is disposed resting on a base frame that suits with the
foundation at the bottom and machine with stator and bearing at the top.
2. The 'universal make shift generator' as claimed in claim 1 wherein the intermediate
coupling size changes from site to site.
3. The universal make shift generator as claimed in claim 1 wherein the front coupling
flange of intermediate coupling is made suiting to the turbine coupling.
4. The universal make shift generator as claimed in claim 1 wherein the rear side
coupling flange of intermediate coupling matches with the rotor drive side coupling
flange of make shift generator.

5. The make shift generator as claimed in claim 1 wherein the length of the
intermediate coupling is decided based on the distance between the turbine and make
shift generator coupling flange.
6. The universal make shift generator as claimed in claim 1 wherein the replacement
generator is provided with either static or brushless excitation and matching with the
existing output terminal location.
7. The universal make shift generator as claimed in claim 1 wherein the base frame is
made by fabrication work comprising of I-beams and channel welded together wherein
the length of the channel can be increased or decreased by sliding the channel on the I-
beam before welding.

ABSTRACT

A universal make shift generator that replaces generator at site and needs to be
sent for serving having arrangement comprising:
and shield mounted bearings in place of pedestal mounted bearings in order to reduce
the generator rotor length;
an intermediate coupling installed in the space created by reduction in generator rotor
length between the turbine and generator to cater to the lateral and torsional analysis
requirement;
radial rib provided on the non drive and to create more space in the output terminal
zone;
the make shift generator is disposed resting on a base frame that suits with the
foundation at the bottom and machine with stator and bearing at the top.