BHEL HARIDWAR VOCATIONAL TRAINING REPORT
“BHARAT HEAVY ELECTRICAL S LIMITED”
Submitted By :
MNIT ,JAIPUR (RAJ.)
“An engineer with only theoretical knowledge is not a complete engineer.
Practical knowledge is very important to develop and to apply engineering
skills”. It gives me a great pleasure to have an opportunity to acknowledge and
to express gratitude to those who were associated with me during my training at
Special thanks to Mr. Tariq Husan for providing me with an opportunity to
undergo training under his able guidance.
I express my sincere thanks and gratitude to BHEL authorities for allowing me
to undergo the training in this prestigious organization. I will always remain
indebted to them for their constant interest and excellent guidance in my
training work, moreover for providing me with an opportunity to work and gain
2.BHEL’S CONTRIBUTION IN DIFFERENT SECTORS
3. BHEL HARIDWAR – AN OVERVIEW
4. TURBO GENERATORS
i) STATOR FRAME
ii) STATOR CORE
iii) STATOR WINDING
iv) END COVERS
i) ROTOR SHAFT
ii) ROTOR WINDING
iii) ROTOR RETAINING RINGS
iv) ROTOR FANS
d) VENTILATION AND COOLING
e) EXCITATION SYSTEM
g) MOTOR WINDING
BHEL - AN OVERVIEW
In 1956 India took a major step towards the establishment of its heavy engineering
industry when Bharat Heavy Electricals Limited, the first heavy electrical manufacturing unit
of the country was set up at Bhopal. It progressed rapidly and three more factories went into
production in 1956 .The aim of establishment BHEL was to meet the growing power
requirement of the country.
BHEL has supplied 97% of the power generating equipment that was commissioned
in India during 1979-80. BHEL has supplied generating equipment to various utilities capable
of generating over 18000MW power. BHEL is one of the largest power plant equipment
manufacturing firms in India and it ranks among the top ten manufacturers globally. BHEL
has covered up many power stations over 40 countries worldwide.
BHEL has its head quarters at New Delhi. Its operations are spread over 11
manufacturing plants and number of engineering and service divisions located across the
country. The service division includes a network of regional offices throughout India.
BHEL’S UNIT IN INDIA
S.No. PLACE UNITS (PLANTS)
1. HARDWAR 2
2. BHOPAL 1
3. JHANSI 1
4. JAGDISHPUR 1
5. HYDERABAD 1
6. BANGALORE 3
7. RANIPET 1
8. RUDRAPUR 1
A BRIEF HISTORY
The first plant of what is today known as BHEL was established nearly 40 years ago at
BHOPAL and was genesis of Heavy Electrical Equipment industry in India. BHEL is today
the largest engineering enterprise of its kind in India, with a well recognized track record of
performance making profits continuously since 1971-72. It achieved a sales turnover of
Rs.1022 core in 1997-98. BHEL caters to core sectors of the Indian Economy via, Power,
Industry, Transportation, Defense, etc.
The wide network of BHEL’s 14 manufacturing divisions, 9 service centers & 4 power
Sector Regional centers & about 150 project sites enables the service at competitive prices.
Having attained ISO 9000 certification, BHEL is now embarking upon the Total Quality
Management. The company’s inherent potential coupled with its strong performance over the
years, has resulted in it being chosen as one of the ― Maharatna PSUs(on 1 February 2013 ),
which are to be supported by the Government in their endeavor to become future global players. It
is the 7th largest power equipment manufacturer in the world. In the year 2011, it was ranked
ninth most innovative company in the world by US business magazine Forbes. BHEL is the only
Indian Engineering company on the list, which contains online retail firm Amazon at the second
position with Apple and Google at fifth and seventh positions, respectively. It is also placed at 4th
place in Forbes Asia's Fabulous 50 List of 2010
BHEL’S CONTRIBUTION IN DIFFERENT
Power sector comprises thermal, nuclear, gas & hydro power plant business. Today,
BHEL supplied sets account for nearly 56,318 MW or 65% of the total installed capacity of
86,636 MW in as against nit till 1969-1970.
BHEL has proven turnkey capabilities for executing power projects from concept to
commissioning. It posses the technology and capability to produce thermal power plant
equipments up to 1000MW rating and gas turbine generator sets up to a unit rating of 240
MW. Cogeneration and combined cycle plants have been introduced to achieve higher plant
efficiencies. To make efficient use of the high ash content coal available in India, BHEL
supplies circulating fluidized bed boilers to thermal and combined cycle power plants. BHEL
manufacturers 235 MW nuclear turbine generator sets and has commenced production of 500
MW nuclear turbine generator sets. Custom-made hydro sets of Francis, Pelt on and Kaplan
types for different head-discharge combinations are also engineered and manufactured by
BHEL is based upon contemporary technology comparable to the best in the world & is also
BHEL also supplies a wide range of transmission products and systems up to 400 KV
Class. These include high voltage power and distribution transformers, instrument
transformers, dry type transformers, SF6 switchgear, capacitors, and insulators etc. For
economic transmission bulk power over long distances, High Voltage Direct Current
(HVDC) systems are supplied. Series and Shunt Compensation Systems have also been
developed and introduced to minimize transmission losses.
A strong engineering base enables the Company to undertake turnkey delivery of electric
substances up to 400 kV level series compensation systems (for increasing power transfer
capacity of transmission lines and improving system stability and voltage regulation), shunt
compensation systems (for power factor and voltage improvement) and HVDC systems (for
economic transfer of bulk power). BHEL has indigenously developed the state-of-the-art controlled
shunt reactor (for reactive power management on long transmission lines). Presently a 400 kV Facts
(Flexible AC Transmission System) project under execution.
A high percentage of trains operated by Indian Railways are equipped with BHEL’s
traction and traction control equipment including the metro at Calcutta. The company
supplies broad gauge electrical locomotives to Indian Railways and diesel shunting
locomotives to various industries.5000/6000 hp AC/DC locomotives developed and
manufactured by BHEL have been leased to Indian Railways. Battery powered road vehicles
are also manufactured by the company.
BHEL’s products, services and projects have been exported to over 50 countries
ranging from United States in the west to New Zealand in far East. The cumulative capacity
of power generating equipment supplied by BHEL outside India is over 3000MW. The
company’s overseas presence includes projects in various countries. A few notable ones are :
150 MW (ISOI) gas turbine to Germany, utility boilers and open cycle gas turbine plants to
Malaysia, Tripoli-west, power station in Libya executed on turnkey basis, thermal power
plant equipment to Malta and Cyprus, Hydro generators to new Zealand and hydro power
plant equipment to Thailand. BHEL has recently executed major gas-based power projects in
Saudi Arabia and Oman, a Boiler contract in Egypt and several Transformer contracts in
Malaysia and Greece
Technologies offered by BHEL for non-conventional and renewable sources of
energy include: wind electric generators, solar photovoltaic system, stand alone and grid-interactive
solar power plants, solar heating systems, solar lanterns and battery-powered road vehicles. The
company has taken up R&D efforts for development of multi-junction amorphous solar cells and
fuel cells based systems.
BHEL is a major contributor of equipment and systems to industries: cement, sugar, fertilizer,
refineries, petrochemicals, paper, oil and gas, metallurgical and process industries. The company is
a major producer of large-size thyristor devices. It also supplies digital distributed control system
for process industries and control & instrumentation systems for power plant and industrial
application. The range of system & equipment supplied includes: captive power plants, co-
generation plants DG power plants, industrial steam turbines, industrial boilers and auxiliaries.
Water heat recovery boilers, gas turbines, heat exchangers and pressure vessels, centrifugal
compressors, electrical machines, pumps, valves, seamless steel tubes, electrostatic
precipitators, fabric filters, reactors, fluidized bed combustion boilers, chemical recovery boilers
and process controls.
The Company is a major producer of large-size thruster devices. It also supplies digital distributed
control systems for process industries, and
control & instrumentation systems for power plant and industrial applications. BHEL is the only
company in India with the capability to make simulators for power plants, defense and other
At the foothills of the majestic Himalayas & on the banks of a holy Ganges in Ranipur near
HARIDWAR is located Heavy Electricals Equipment Plant of Bharat Heavy electrical Ltd.
BHEL, wholly owned by the government of India is an integrated engineering
complex consisting of several plants in India, where about 70,000 workers are busy in design
& manufacturing of a wide range of heavy electrical equipment. At present 70% of the
Country’s electrical energy is generated by the sets manufacturing by BHEL, Haridwar
BHEL HARDWAR is broadly divided in to two parts:
A) - CFFP: – Central Foundry Forge Plant B) - HEEP: – Heavy Electrical Equipment Plant
A) - CFFP is divided in to following shops:
Steel Melting Shop (SMS)
Cast Iron (CI) Foundry
B) - HEEP is divided into following blocks:
BLOCK-1 Turbo Generators, AC Machines
BLOCK-2 Fabrication (Steam, Hydro & gas Turbine)
BLOCK-3 Gas & Steam Turbine
BLOCK-4 CIM (Coil & Insulation Manufacturing) & ACG (Apparatus control Gear)
BLOCK-5 Heat exchangers, Forging and Fabrication
BLOCK-7 Wooden Packing works
BLOCK-8 Fabrication, seamless tubes and heat exchanger
The AC generator or alternator is based on the principle of electromagnetic
induction and consist generally of a stationery part called Stator and a rotating
part called Rotor. Stator houses the armature winding. The rotor houses the
field winding. DC voltage is applied to field winding through the slip rings.
When the rotor rotates, the lines of magnetic flux cut through the winding. This
induces an electromagnetic EMF in the stator winding. The magnitude of emf is
given by following formula
E = 4.44* ø *ƒ*N volt
ø = strength of magnetic field
ƒ = frequency in hertz
N = number of turn in stator winding
ƒ = frequency = P*n / 120
P = number of poles
n = number of revolution per second of rotor
SYNOPSIS OF THE FUNCTION OF TURBO GENERATOR :
The generator rotor is driven by prime mover and on driver side gas/
diesel/ steam hydro depending on the equipment to which it is meant for.
The non-drive side of rotor is equipped with a rotating side of armature
which produces AC voltage. This is rectified to DC by using a DC
commutator / rotating diode wheel depending upon the type of exciter.
The rear end of above exciter armature is mounted with a permanent
magnet generator rotor.
As the above rotating system put into operation, the PMC produces AC
The voltage is rectified by thyristor circuit to DC.
This supply is given to exciter field. This field is also controlled by taking
feedback from main generator terminal voltage, to control exciter field
variation by automatic voltage regulator. The rectified DC supply out of
exciter is supplied to turbo generator rotor winding either through
brushes or central which will be directly connected to turbo generator.
This depends on the type of exciter viz. DC commutator machines or
The main AC voltage of generator is finally available to turbo generator
LARGE SIZE TURBO GENERATOR (LSTG)
These types of generators are those which has taken steam turbine. Their prime
mover and current is supplied by exciter system.
Main types are:-
Basic terms are:-
T = turbo generator
A = air cooled
H = hydrogen cooled
R = radial cooling with gas
D = direct axial cooling with gas
F = direct axial cooling with water
I = indirect cooling
COMPONENTS OF T.G. :-
Rotor retaining rings.
The generator stator is a tight construction supporting and enclosing stator
winding, core and hydrogen cooling medium. Hydrogen is contained within
frame and circulated by fans mounted at either end of rotor. The generator is
driven by direct coupled steam turbine at the speed of 3000 rpm.The generator
is designed for continuous rated output. Temperature detector and other device
installed or connected within machine, permit the windings core and hydrogen
temperature, pressure, and purity in machine.
STATOR FRAME –
Stator body is a totally enclosed gas tight fabricated structure made up of high quality mild
steel and austenitic steel. It is suitably ribbed with annular rings in inner walls to ensure
high rigidity and strength and it also help to reduce vibration and to withstand the gas
thermal pressure .The arrangement, location and shape of inner walls is determined by the
cooling circuit for the flow of the gas and required mechanical strength and stiffness. The
natural frequency of the stator body is well away from any of exiting frequencies. Inner and
sidewalls are suitably blanked to house for longitudinal hydrogen gas coolers inside the
stator body. It supports the laminated core and winding the stator comprises an inner
frame and outer frame. The inner cage is usually fixed in the yoke by an arrangement of
spring to damper the double frequency vibrations inherent in two pole generator.
The fabricated inner cage is inserted in the outer frame after the stator core has been
constructed and the winding completed. Footings are provided the stator foundation
shields enclose the ends of heavy end frame and form mounting of generator bear and
radial shaft. R is subdividing the frame and axial members to form ducts from which the
cooling given to end from radial duct in the core and is recirculated. The horizontally
mounted water cooled gas coolens being so arranged the it may be cleaned on the water
side without opening the machine to atmosphere. All welded joints exposed to hydrogen
are specially made to prevent leakage. The complete frame is subjected to hydraulic test at
a pressure of 7 atm.
STATOR CORE –
It consists of thin laminations. Each lamination made of number of individual segments.
Segments are stamped out with accurately finished die from the sheets of cold rolled high
quality silicon steel.Before insulation on with varnish each segment is carefully debarred.
Core is stacked with lamination segments. Segments are assembled in an interleaved
manner from layer to layer for uniform permeability. Stampings are held in a position by
20 core bars having dovetail section. Insulating paper pressboards are also put between the
layer of stamping to provide additional insulation and to localize short circuit. Stampings
are hydraulically compressed during the stacking procedure at different stages. Between
two packets one layer of ventilating segments is provided. Steel spacers arespot welded on
stamping. These spacers from ventilating ducts where the cold hydrogen from gas coolers
enter the core radialy inwards there by taking away the heat generated due toeddy current
losses. The pressed core is held in pressed condition by means of two massive non-
magnetic steel castings of press ring. The press ring is bolted to the ends of core bars. The
pressure of the pressure ring is transmitted to stator core stamping through press fringes of
non-magnetic steel and duralumin placed adjacent to press ring. To avoid-heating of press
ring due to end leakage flow two rings made of copper sheet are used on flux shield. The
ring screens the flux by short-circuiting. To monitor the formation of hot spots resistance
transducer are placed along the bottom of slots. To ensure that core losses are within limits
and there are no hot spots present in the core. The core losstest is done after completion
of core assembly.
The main features of core are –
1. To provide mechanical support
2. To carry efficiently electric, magnetic flux.
3. To ensure the perfect link between core and rotor.
STATOR WINDING –
The stator has a three phase, double layer, short pitched and bar type of windings having
two parallel paths. Each slots accommodated two bars. The slot lower bars and slot upper
are displaced from each other by one winding pitch and connected together by bus bars
inside the stator frame in conformity with the connection diagram. Each bar consists of
solid as well as hollow conductor with cooling water passing through the latter. Alternate
arrangement hollow and solid conductors ensure an optimum solution for increasing
current and to reduce losses. The conductors of small rectangular cross section are
provided with glass lapped strand insulation. A separator insulates the individual layers
from each other. The transposition provides for mutual neutralization of voltage induced in
the individual strands due to the slots cross field and end winding field. The current flowing
through the conductor is uniformly distributed over the entire bar cross section reduced.
To ensure that strands are firmly bonded together and give dimensionally stability in slot
portion, a layer of glass tape is wrapped over the complete stack. Bar insulation is done
with epoxy mica thermosetting insulation. This insulation is void free and posses better
mechanical properties. This type of insulation is more reliable for high voltage. This
insulation shows only a small increase in dielectric dissipation factor with increasing test
voltage. The bar insulation is cured in an electrically heated process and thus epoxy resin
fill all voids and eliminate air inclusions.
INSULATION OF BARS –
Vacuum pressed impregnated mica elastic high voltage insulation:
The voltage insulation is provided according to the proven resin poor mice base of thermo
setting epoxy system. Several half overlapped continuous layer of resin poor mica tape are
applied over the bars. The number of layers or thickness of insulation depends on the
machine voltage. To minimize the effect of radial forces windings hold and insulated rings
are used to support the overhang.
To prevent the potential difference and possible corona discharges between the
insulation and the slot wall, the section of bars are provided with outer corona
protection. The protection consists of polyester fluce tape impregnated in epoxy resin
with carbon and graphite as fillers. At the transition from the slot to the end winding
portion of the stator winding portion of stator bars a semiconductor tape made up old
polyester fluce is impregnated.
Resistance temperature detector :
The stator slots are provided with platinum resistance thermometer to record and
watch the temperature of stator core and tooth region and between the coil sides of
machine in operation. All AC machines rated for more than 5 MVA or with
armature core longer the machine is to be provided with at least 6 resistance
thermometers of their couples which shall built inside the stator suitably distributed
among the circumference at the likely hottest point. The thermometer should be
fixed in the slot but outside the coil insulation. When the winding has more than
one coil side per slot, the thermometer is to be placed between the insulated coil
sides. The length of the resistance thermometer depends upon the length of
armature. The leads from the detectors are brought out and connected to the
terminal board for connection to temperature meter or relays operation of RTD is
based on the prime that the “electric resistance of metallic conductor varies linearly
END COVERS –
The end covers are made up of fabricated steel or aluminum castings. They are employed
with guide vans on inner side for ensuring uniform distribution of air or gas.
Rotor revolves in most modern generator at speed of 3000 revolutions per minute. It is
also as electromagnet and to give it necessary magnetic strength, the winding must carry
a very high current. The passage of current through windings generates heat. But the
temperature must not be allowed to become too high, otherwise difficulties will be
experienced with insulation. To keep the temperature cross section of the conductors
could not be increased but this would introduce another problems. In order to make
room for large conductor, body and this would cause mechanical weakness. With good
design and great care this problem can be solved.
ROTOR SHAFT –
Details of shaft are given here –
Length = 9 meter (approx.)
Diameter = 1 meter (approx.)
Material – alloy steel
Number of poles = 2
The rotor shaft is cold rolled forging 26N1 or MOV116 grade and it is imported
from Japan and Italy.
Rotor shaft is a single piece forming manufactured castings. It is forged from a vacuum cast
steel slots for insulation of the field winding are made into the rotor body. The longitudinal
slots are distributed over the circumference. To ensure that a high quality product is
obtained, strength of material analysis and ultrasonic are performed during the
manufacturing rotor. The high mechanical stress resulting from the centrifugal force and
short circuit, torque called for a high specified mechanical and magnetic properties as well
as homogenous forging. After completion, the rotor is balanced in the various planes and
different speed and then subjected to an over speed test at 120% of rotor speed. The rotor
consist of electrically active portion and two shaft end approximately 60 b% of rotor body
circumference have longitudinal slots which holds the field winding. Slots pitch is selected
so that the two solid poles are displaced by 180 degree the rotor wedges act as damper
winding within the range of winding slots. The rotor teeth at the rotor body are provided in
radial and axial poles enabling cooling air to be discharged.
ROTOR WINDING –
The winding consist of several coils inserted into the slots and the series connected
such that two coils group to form one pole. Each coil consist of several series
connected turns each of which consist of two half turns connected by brazing in end
section. The individual turn of coil are insulated against each other by interlayer
insulation. L-shaped strip of laminated epoxy glass fiber with nomex filter are used
for slot insulation.
The slot wedges are made up of high electrical conductivity material and thus act as
damper winding. At their ends, the slots wedges are short circuited through the rotor body.
When rotor is rotating at high speed, the centrifugal forces tries to lift the winding out of
slots, they are contained by wedges.
The field winding consist several series connected coils into the longitudinal slots of body.
The coil are wound that two poles are obtained. The solid conductors have a rectangular
cross-section and are provided axial slots for radial or cooling air. All conductors have
identical copper and cooling section.
CONDUCTOR MATERIAL –
The conductors are made up of copper with silver content of approx. 0.1% . As
compared to electrolytic copper silver alloyed copper features high strength
properties at high temperature so that coil deformations due to thermal stresses are
eliminated. The conductors are made of hard drawn silver bearing copper. The
rectangular cross section copper conductors have ventilating ducts on the two sides
thus providing a channel for hydrogen flow. Two individual conductors placed-one
over the other are bent to obtain half turns. Further these half turns are brazed in
series to form coil on the rotor model
The insulation between the individual turns is made up of layer of glass fiber laminate the
coils are insulated from the rotor body with L-shaped strip of glass fiber laminate with
nomex interlines to obtain the required leakage path between the coil and rotor body thick
top strips of glass fiber laminate are inserted below wedge. The top strip are provided with
axial slots of same cross-section and spacing and used on the rotor winding.
END WINDING BRACING –
The spaces between the individual’s coils in the end working are with insulated members
that prevent coil movement the insulation by H or L high glass lamination.
ROTOR RETAINING RINGS –
The centrifugal forces of the end windings are contained by piece rotor retaining rings.
Retaining rings are made u of non-magnetic high strength steeling order to reduce the stray
losses. Each retaining rings with its shrink fitted. Insert ring is shrunk on the rotor is an
overhang position. The retaining ring is secured in the axial position by snap rings. The
rotor retaining rings withstand the centrifugal forces due to end winding. One end of each
ring is shrunk fitted on the rotor body while the other hand overhangs the end winding
without contact on the rotor shaft. This ensures unobstructed shaft deflection at end
windings. The shrunk on hub on the end of the retaining ring serves to reinforce the
retaining ring and serves the end winding in the axial direction. At the same time, a snap
ring is provided against axial displacement of retaining ring. The shrunk slot of current. To
reduce the stray losses and have high strength, the rings are made up of non-magnetic cold
ROTOR FANS –
The cooling air in generator is cold by two axial flow fans located at the rotor shaft one at
each end augment the cooling of the winding. The pressure established by the works in
conjunction with the expelled from the discharge path along the rotor. The blades of fan
have threaded roots for screwed into the rotor shaft. Blades are drop forged from
aluminum alloy. Threaded root fastenings permit angle to be changed. Each blade is
screwed at its root with a threaded pin.
The turbo generators are provided with pressure lubricated self-aligning type bearing
to ensure higher mechanical stability and reduced vibration in operation. The
bearings are provided with suitable temperature element due to monitor bearing
metal temperature in operation.
The temperature of each bearing monitored with two RTD’s (resistance thermo detector)
embedded in the bearing sleeve such that the measuring point is located directly below
Babbitt. These RTDs are monitored temperature scanner in the control panel and if the
temperature exceeds the prescribe limit. Bearing have provision for vibration pickup to
monitor shaft vibration.
To prevent damage to the journal due to shaft current, bearings and coil piping on either
side of the non-drive and bearings are insulated from the foundation frame. For fascinating
and monitoring the healthiness of bearing insulation, shaft insulation is provided.
VENTILATION AND COOLING SYSTEM
The machine is designed with ventilation system having rated pressure. The axial fans
mounted on either side of rotor ensure circulation of hydrogen gas. The rotor is designed
for radial ventilation by stem. The end stator is packets and core clamping and is
intensively cooled by through special ventilation system. Design of special ventilation is to
ensure almost uniform temperature of rotor windings stator core. Embedded resistance
temperature detector do continuous monitoring of hydrogen temperature at part of
COOLING SYSTEM –
STATOR COOLING SYSTEM –
The stator winding is cooled by distillate water which is fed from one end of the machine
by Teflon tube and flows through the upper bar and returns back through the lower bar of
a slot. Turbo generator requires water cooling arrangement over and above the usual
hydrogen cooling arrangement. The stator is cooled in this system by circulating
demineralized water trough hollow conductors. The cooling was used for cooling of stator
winding and for the use of very high quality of cooling water. For this purpose DM water of
proper specifying resistance is selected. Generator is to be loaded within a very short
period. If the specific resistance of cooling DM water goes beyond preset value. The
system is designed to maintain a constant rate cooing water flow through the stator winding
at a nominal inlet with temperature of 40 degree centigrade. As it is look working, the
cooling water is again cooled by water which is also demineralized to avoid contamination
with any impure water in case of cooler tube leakage the secondary DM cooling water is in
turn cooled by Clarified water taken from clarified water header.
ROTOR COOLING SYSTEM –
The rotor is cooled by means of gap pickup cooling, where in the hydrogen gas in the
air gap is sucked through the scoops on the rotor and is directed to flow along the
ventilating canals milled on the sides of the rotor coil, to the bottom of slot where it
takes a turn and comes out on the similar canal milled on the other side of the rotor coil
to the hot zone of the rotor, Due to the rotation of the rotor, a positive section as well as
discharge is created due to which a certain quantity of a gas flow and cools the rotor.
The method of cooling gives uniform distribution of temperature. Also this method has
an inherent of eliminating the deformation of copper due to varying temperature.
HYDROGEN COOLING SYSTEM –
Hydrogen is used as a cooling medium in large capacity generally in views of high
heat carrying capacity and low density. But in views sits forming an explosive mixture
with oxygen. Proper arrangement for puring, maintaining the purity in the generator
have to be made. Also in order to prevent used hydrogen from generators, casing,
sealing system is used to provide oil sealing. The system is capable of performing
following system –
1. Filing in and purging of hydrogen safety without bringing in contact with air.
2. Maintaining the gas pressure inside the machine at the desired value at all the
3. Provide indication to the operator about the condition of the gas inside the machine
i.e. the pressure, temperature and purity.
4. Continuous circulation of gas inside the machine through a drier in order to remove
any water vapor that may be present in it
5. Indication of liquid level in the generator and alarm in case of high level.
6. GENERATOR SEALING SYSTEM –
Seals are employed to prevent the leakage pf hydrogen from the stator at the point of
rotor exit. A continuous film between a rotor collar and the seal liner is maintained by
measurement of the oil at pressure above the casing hydrogen gas pressure
The basic use of given exciter system is to produce necessary DC for turbo generator
system. Principal behind this that PMG is mounted on the common shaft which
generate electricity and that id fed too yoke of main exciter
This exciter generates electricity and this is of AC in nature. This AC is that converted into
DC and is that fed to turbo generator via C/C volt for rectifying purpose. We have for RC
bock and diode circuit. The most beautiful feature is of this type of exciter is that is
automatically divides the magnitude of current to be circulated in rotor circuit. This
happens with the help of AVR regulator which means automatic voltage regulator. A
feedback path is given to this system which compares theoretical value to predetermine and
then it sends the current to rotor as per requirement.
The brushless exciter mainly consists of:-
1. rectifier wheels
2. three phase main exciter
3. three phase pilot exciter
4. Metering and supervisory equipment.
The brushes exciter is an AC exciter with rotating armature and stationery field. The
armature is connected to rotating rectifier brides for rectifying AC voltage induced to
armature to DC voltage. The pilot exciter is a PMG (permanent magnet generator). The
PMG is also an AC machine with stationery armature and rotating field. When the
generator rotates at the rated speed, the PMG generates 220 V at 50 hertz to provide power
supply to automatic voltage regulator.
A common shaft carries the rectifier wheels the rotor of main exciter and the permanent
magnet rotor of pilot exciter. The shaft is rigidly coupled to generator rotor and exciter
rotors are than supported on these bearings.
1. This procedure is for high voltage test on stator winding of turbo generator.
This procedure covers the high voltage test on stator winding.
This test is conducted to check whether the insulation is properly plced or
not. The insulation placed over the winding should be such that they make
half overlap with next wrapping of the tape. This test is exclusively conducted
to test the health lines of insulation of winding
2. Test procedure for high voltage on rotor winding of TG.
This produces the high voltage test on rotor winding
This test is conducted to check whether the insulation is properly placed or
3 This procedure for measurement of DC resistance of stator and rotor
winding of TG.
This procedure covers the measurement of DC resistance of stator winding.
This test is connected to measure the resistance content present in the conducting
material of stator and rotor.
3 Test procedure for measurement of impedance of rotor winding with 50
This procedure covers the measurement of impedance of rotor winding 50
TEST EQUIPMENTS –
1. 50 hertz power frequency AC source
2. AC voltmeter (0-30, 75, 150)
3. AC ammeter (0-5 ampere)
5. Current transformer (50/5 A)
6. Connecting leads
Z = V/I ohm
Z = Impedance in ohm
V = Voltage in volts
I = Current in ampere
With 50 hertz, this test id done in following condition –
1. Rotor outside the stator at standstill.
2. Rotor inside the stator at standstill.
3. Rotor inside the stator at speed 1/3, 2/3, 3/3 of rated speed.
IMPEDENCE WITH 50 HERTZ -
As the impedance of the rotor winding depends on physical geometry of the rotor, it is not
possible to fix at particular value for acceptance, but a peculiar characteristics that
impedance increases with increase of voltage can be assured value of increase is less in
cylindrical rotor that in salient pole rotors
5 .Test procedure for measurement of leakage reactance of TG stator
This procedure covers the leakage reactance measurement of stator winding after
completion of winding.
1. To determine total leakage reactance Xl.
2. To determine core leakage reactance Xc.
3. To compute potier reactance Xd.
6. Test procedure for capacitance measurement of stator winding.
The procedure covers the measurement of capacitance per phase with respect to ground of
the stator winding.
To generate reference value for comparison in future at site.
The stator winding have two values of capacitances.
1. Cg – capacitance with respect to ground called ground capacitance.
2. Cm – capacitance with respect to other winding called mutual capacitance.
HELIUM LEAK TEST –
To check any leakage of gas from stator and rotor as if there is any leakage of
gas used for cooling such as hydrogen then it may cause an explosion.
1. Count the coil groups in the anti clock wise direction locking from the connection
2. Leads of the coils groups lying on the outer periphery of the overhang position shall
be the finish and those lying on the inner periphery shall be the start to coil groups.
3. Leads shall be taken form the coil side lying at inner periphery of slot No.1.
4. The coil group No.1 shall Lie at top with its axes coinciding with the vertical axis of
5. Take out terminal leads 02 U2, V2, W2 for left hand side terminal box and 02 U1,
V1, W1 for right hand side terminal box. When looking form the connection end.
WINDING DIAGRAM OF MOTOR
Winding data :
NO. OF PHASE 3
NO. OF POLES 6
PHASE CONNECTION Y
Connection of motor winding :
NO. OF PARELLEL PATH 2
NO. OF COIL GROUP 18
Training at B.H.E.L. has proved to be quite faithful. It proved an opportunity
for encounter with such huge machine like turbo-generators.
The architecture of B.H.E.L., the way various units are linked and the way
working of whole plant is controlled make the students realize that Engineering is not just
structural description but greater part is planning and management. It provides an
opportunity to learn tech. Used at proper place and time can save a lot of labour.
But there are few factors that require special mention. Training is not carried
in true spirit. It is recommended that there should be projectors especially for trainees
where presence of authorities is ensured.
However, training has proved to be satisfactory. It has allowed us an opportunity to
get an exposure of the practical implementation of theoretical fundamentals.