FIELD OF INVENTION:-
Turbogenerator have two main components, the stator and the
rotor. The field of 210 MW turbogenerator (TG) is in the rotor,
which receives 440V D.C. from the exciter rotor mounted on the
same shaft. The 440V D.C. from exciter is fed to the rotor
through current carrying bolts (cc bolts). The cc bolts are silver
plated and free from any varnish coating. They are also insulated
with vacuum pressure impregnated glass tapes. Such insulation
are required to withstand 8 KV for one minute. The present
invention relates to an improved device for High Voltage testing
of the cc bolts in a batch instead of testing them one at a time as
was done in prior art.
BACKGROUND OF THE INVENTION:-
High voltage withstand capacity of glass insulation of the CC
(current carrying) bolts are very vital for proper functioning of the
turbogenerator for obvious reasons. As such they are required to
be tested meticulously to avoid any breakdown of the. generator.
Standard HV tests and other specified test are carried out on the
CC bolts individually in absence of any testing equipment for
carrying out the test in a batch. No fixture or arrangements was
available for performing High Voltage test on Current Carrying
(CC) Bolt. The test was performed individually on each CC Bolt
with temporary connections. The present invention introduces a
fixture by which the standard tests may be carried out in a batch
to avoid the repetitive process of carrying out the same set of
test one by one, wasting valuable time. One object of the
invention is to expedite the testing process by having a fixture
which can simultaneously test plurality of CC bolts and save
costly production time.
Another object of the invention is to ensure identical input to the
test pieces by subjecting them to the same testing platform at a
time.
Intangible gains of new method over old:-
Plurality of CC Bolts can be tested at a time over single CC Bolt
testing.
Time cycle reduction.
Customer Satisfaction.
Safety of CC Bolts because of proper stands on fixture.
No loose parts which may cause spark over while performing the
HV test.
ACCOMAPYING IN DRAWING:-
Fig 1 - Prior Art
Fig 2 - Present Invention
Fig 3 - Testing arrangement
DETAIL DESCRIPTION OF THE INVENTION WITH
ACCOMPANYING DRAWING;-
The fixture of present invention as shown in figure 2 essentially
comprises of a platform (1) made up of Epoxy glass laminate
sheet of suitable thickness over which is fitted one Aluminum
sheet (2) of adequate thickness by means of 3 no Epoxy glass
laminated bolts (5). One support (6) made of insulating board is
fitted on the Aluminum sheet (2) for supporting the loop of the
earthing wire which links plurality of CC bolts through wraps of Al
foil on the bolts. Plurality of hexagonal steel bolts (4) are also
fitted on the Aluminum sheet (2) through steel washers. The test
pieces are mounted on the bolts.
Before subjecting the CC bolts at high voltage it is prepared first.
Aluminum foil and copper foils as shown in figure 3 are wrapped
around the mechanical surface in alternate layers and earthling
wire is connected to the Al foil. High voltage is applied to the CC
bolt through a point (3) fixed on the Al sheet for applying High
Voltage. 8 KV is applied for one minute to check whether the
insulation could withstand the impressed High Voltage.
WE CLAIM:-
1.A fixture for high voltage testing of current carrying bolts
(CC bolts) for 210 MW (TG) turbogenerator rotor,
comprising
- one platform (1) of suitable dimension made up of Epoxy
glass laminate sheet over which is fitted another Aluminum
sheet of suitable dimension (2) fitted to the said platform
(1) by 3 no epoxy glass laminate bolts (5) and Aluminum
sheet (2) having hexagonal steel bolts and a point (3) for
application of high voltage fixed on it, the bolt having at
least two layers of Aluminum and an Copper foil wrapped on
it, with Aluminum foils connected by a wire loop to connect
them to earth, the wire loop having an insulating board (6)
fixed on the Aluminum sheet, for supporting the earth
connection wire loop, characterized in that it is provided with
means to test plurality of CC bolts at a time.
2. A fixture for high voltage testing of plurality of current
carrying bolts of 210 MW turbogenerator rotor as
substantially described herein with reference to the
accompanying drawings.

A fixture for high voltage testing of (CC) Current Carrying bolt of
210 MW turbogenerator rotor. The D.C, current from the exciter
is fed to the 210 MW turbogenerator rotor through current
carrying bolt at the rotor. The insulation on the CC bolts are
required to withstand 8 KV r.m.s for one minute. The fixture of
the present invention can test a plurality of CC bolts instead of
carrying them one at a time as was done on prior art.