A Presentation On Construction Of
Turbo Generator
contents

Introduction
 Working principle of turbo generator
 Types of turbo generator
 General components of turbo generator
 Manufacturing process of conductors
 Testing of turbo generator
Introduction
A turbo generator is a mechanical device that is used to produce electrical power. It
does so by turning a large turbine that is connected to a generator, which converts
mechanical energy into electrical energy.
They are mostly used as large capacity generator driven by steam/gas turbine. They are
of three types namely:1.
Steam turbine generator
2.
Gas turbine generator
3.
Hydro turbine generator
Working principle of
turbo generator
The generator works on the principle of
ELECTROMAGNETIC INDUCTION. A turbo generator is
a turbine directly connected to the shaft of an electric
generator, when a turbine is attached to the electrical generator
the kinetic energy of the steam pushes against the fan-type
blades of the turbine, causing the turbine, and therefore the
attached rotor of the electrical generator, to spin and produce
electricity.
Working principle of Turbo Generator
Types of turbo
generator
According to cooling system turbo generator are divided asi.
THRI
ii.
TARI
iii.
THDI
iv.
THDD
v.
THDF
vi.
THFF
T = turbo generator
H/A = the cooling media used i.e. hydrogen gas or air.
R/D/F/I = the type of cooling of rotor i.e. radial, indirect, forced, direct
I/D/F = the type of cooling of stator i.e. indirect, direct, forced.
The General Components
of a turbo generator:





Stator
Stator
frame
Stator
core
Stator
winding
Bushing
Excitation
system






Rotor
Rotor shaft
Rotor
winding
Retaining
ring
Rotor
wedges
Rotor fan
Stator frame
Stator body is totally
enclosed gas tight
fabricated structure made
up of high quality mild
steel and austenitic steel.
 It is the heaviest section
in the generator.
 It also help to reduce
vibration and to withstand
the gas thermal pressure.

Stator core




Stator core is consists of thin lamination. Each
lamination made of number of individual
segment. Each lamination layer is made of
individual section.
The main feature of core areTo provide mechanical support.
To carry efficiently electric, magnetic flux.
In order to reduce hysteresis losses steel alloy
is used for building up of core.
In order to reduce eddy current thin
laminations are used.
Assembly of Core
Stator winding


Stator winding has a three phase, double layer winding with
the pitch of the winding so adjust as to reduce the 5th and 7th
harmonics .
Each slots accommodated two bars.

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.
Two types of bars are used-
a)
Upper bar
b)
Lower bar
Bushing
The beginning and ends
of the three phase
windings are brought out
from the stator frame
through bushings, which
provides for high voltage
insulation. The bushings
are bolted to the stator
frame at the exciter end.
Rotor Shaft



The rotor shaft is a single piece solid forging
manufactured from a vacuum cast steel.
Slots are made over it.
Approximately 60% of the rotor body circumference
is provided with longitudinal slots , which holds the
field winding.
Rotor winding




The slots houses the field winding
consists of several coils inserted into the
longitudinal slots of rotor body.
The coils are wound so that the two pole
are obtained .
The conductor are made up of copper
with a silver content of approximately
0.1%.
The rectangular cross section copper
conductor have ventilating ducts on the
two sides thus providing a channel for
hydrogen flow.
Rotor wedges:
The rotor of turbo generator is rotating at a very high speed
therefore to protect the winding against the effects from
centrifugal forces they are secured firmly by rotor slot
wedges.
The slots wedges are made of copper alloy .
Retaining rings:
To protect the end winding of rotor from flying out from
rotor due to centrifugal forces rotor retaining rings are used.
Retaining rings are made from high tensile non- magnetic
alloy steel forgings in order to reduce stray losses .
Rotor fan

The cooling air in
generator is circulated
by axial fans located on
the rotor shaft.

In 250 MW rotor two
axial flow fans are
located on both turbine
as well as exciter end
side whereas in 500 MW
axial fans are located on
turbine end side only.
Assembly of Turbo
Generator
After the manufacturing of
both the stator and rotor,
these are assembled together
on assembly bed.
Excitation System
The process of generating a magnetic field by means of an electric current is called
excitation. Turbo generator is a doubly excited machine. The purpose of excitation
system is to continuously provide the appropriate amount of D.C field current to
the generator field winding. Mostly brushless excitation is used.
The brushless exciter has mainly two parts such as1. permanent magnetic pilot exciter
2. three phase main exciter
Cooling system
1.
2.
3.
Cooling system is used to dissipate the heat
generated by various losses and to prolong
the life of insulating material.
Cooling system is divided three parts such
asAir cooling
Hydrogen cooling
Water cooling
Manufacturing process
of conductors
1.
2.
3.
4.
5.
6.
7.
Insulation check
Conductor cutting
Transposition
Cross over
insulation
Stack Pressing
Forming
End Conductor
cutting
8. Pickling process
9. Brazing of coil
lugs
10.Contact sleeve
mounting
11.Reforming
12.Impregnation
13.Insulation
14.Finishing
Testing of turbo
generator
 ELECTRICAL TEST:

Open circuit test

Short circuit test

High voltage test

Inter strand test

MECHANICAL TEST:

Vibration test

Temperature test

Helium test
Thank you