1. 2016
INDUSTRIAL PROJECT REPORT
Electromagnets
Used in Bhilai Steel
Plant.
SUBMITTED BY: - GUIDED BY: -
Nikhil Yadav Mr. Remy Thomas
Electrical and Electronics Engineering Assistant Manager
NIT, Delhi Electrical Repair Shop
BSP, SAIL

2. ACKNOWLEDGEMENT
I take this opportunity to express my profound gratitude and
deep regards to Mr. Remy Thomas(Assistant manager, ERS)
and Mr. R.K. Nayyar(Assistant Manager, MTRS) for their
exemplary guidance, monitoring and constant encouragement
throughout the course of this project.
I am obliged to the officials and workers of ERS and MTRS,
for the insight provided by them and for letting me work on the
equipments. I am grateful for their cooperation during the
period of our assignment.
Lastly, I would like to thank BHILAI STEEL PLANT for
incessant help and also for providing me with all the resources
I needed for this project, without which the completion of this
project would not have been possible.

3. STEEL AUTHORITY OF INDIA LIMITED (SAIL)
BHILAI
This is to certify that “NIKHIL YADAV”; student of Electrical and
Electronics Engineering at National Institute of Technology,
Delhi has completed his Industrial Training Project on
“Electromagnets used in Bhilai Steel Plant”. During the project
he was highly responsive, dedicated and hard working. On the basis
of his interest and devotion towards the assigned tasks and
keenness to complete within stipulated period, I certify him to have
completed the project successfully under my guidance. It was a
great pleasure for me to guide him and share the knowledge.
I wish him great success in life.
Date: Mr. Remy Thomas
Assistant Manager
Electrical Repair Shop
BSP, SAIL

4. BHILAI STEEL PLANT –AN OVERVIEW
Bhilai Steel Plant - a symbolof Indo-Soviet techno-economic collaboration, is
one of the first three integrated steel plants set up by Government of India to
build up a sound base for the industrial growth of the country, The agreement
for setting up the plant with a capacity of 1 MT of Ingot steel was signed
between the Government of erstwhile U.S.S.R. and India on 2nd February, 1955,
and only after a short period of 4 years, India entered the main stream of the
steel producers with the commissioning of its first Blast Furnace on 4th
February, 1959 by the then President of India, Dr Rajendra Prasad.
Commissioning of all the units of 1 MT stage was completed in 1961. A dream
came true-the massive rocks from the virgin terrains of Rajhara were converted
into valuable iron & steel.
In the initial phase the plant had to face many teething problems, mostly
unknown to the workforceat the time, but by meticulous efforts and team spirit,
these problems were surmounted and the rated capacity production was
achieved only within a year of integrated operation of the plant.
Thereafter, the plant was expanded to 2.5 MT capacity per year, and then to 4
MT of crude steel per year, with Soviet assistance.
All the units of the plant have been laid out in sequential formation according to
technological inter-relationship so as to ensure uninterrupted flow of in-process
materials like Coke, Sinter, Molten Iron, Hot Ingots, as well as disposal of
metallurgical wastages and slag etc., minimizing the length of various inter-plant
communications, utilities and services.
BSP is the sole manufacturer of rails and producer of the widest and heaviest
plates in India. Bhilai specializes in the high strength UTS 90 rails, high tensile
and boiler quality plates, TMT bars, and electrode quality wire rods. It is a major
exporter of steel products with over 70% of total exports from the Steel
Authority of India Limited being from Bhilai. The distinction of being the first
integrated steel plant with all major production units and marketable products
covered under ISO 9002 Quality Certification belongs to BSP. This includes
manufacture of blast furnace coke and coal chemicals, production of hot metal
and pig iron, steel making through twin hearth and basic oxygen processes,
manufacture of steel slabs and blooms by continuous casting, and production of
hot rolled steel blooms, billets and rails, structural, plates, steel sections and
wire rods. The plant's Quality Assurance System has subsequently been awarded
ISO 9001:2000.

5. Not content with the Quality Assurance system for production processes, Bhilai
has one in for ISO 14001 certification for its Environment Management System
and its Dalli Mines. Besides environment-friendly technology like Coal Dust
Injection System in the Blast Furnaces, de-dusting units and electrostatic
precipitators in other units, BSP has continued a vigorous afforestation drive,
planting trees each year averaging an impressive 1000 trees per day in the steel
township and mines.
A leader in terms of profitability, productivity and energy conservation, BSP has
maintained growth despite recent difficult market conditions. Bhilai is the only
steel plant to have been awarded the Prime Minister's Trophy for the best
integrated steel plant in the country seven times.
Bhilai Steel Plant, today, is a panorama of sky-scraping chimneys and blazing
furnaces as a modern integrated steel plant, working round the clock, to produce
steel for the nation. Bhilai has its own captive mines spread over 10929.80
acres. We get our iron ore from Rajhara group of mines, 85 kms south-west of
Bhilai. Limestone requirements are met by Nandini mines, 20 kms north of Bhilai
and dolomite comes from Hirri in Bilaspur district, 135 kms east of the plant. To
meet the future requirement of iron ore, another mining site Rowghat, situated

6. about 100 km south of Rajhara, is being developed; as the ore reserves at
Rajhara are depleting.
Bhilai expanded its production capacity in two phases - first to 2.5 MT which was
completed on Sept. 1, 1967 and then on to 4 MT which was completed in the
year 1988. The plant now consists of ten coke oven batteries. Six of them are
4.4 metres tall. The 7 metre tall fully automated Batteries No 9 & 10 are among
the most modern in India. Of Bhilai's seven blast furnaces, three are of 1033 cu.
metre capacity each, three of 1719 cu. metre and one is 2000 cu. metre
capacity. Most of them have been modernised incorporating state-of-the-art
technology. Steel is made through twin hearth furnaces in Steel Melting Shop I
as well as through LD Convertor -continuous Casting route in SMS II. Steel
grades conforming to various national and international specifications are
produced in both the melting shops. Production of cleaner steel is ensured by
flame enrichment and oxygen blowing in SMS I while secondary refining in
Vacuum Arc Degassing ensures homogenous steel chemistry in SMS II. Also in
SMS II is a 130 T capacity RH (Ruhshati Heraus) Degassing Unit, installed
mainly to remove hydrogen from rail steel and Ladle Furnace to meet present
and future requirements of quality steel. Bhilai is capable of providing the
cleanest and finest grades of steel.
The rolling mill complex consists of the Blooming & Billet Mill, Rail & Structural
Mill, Merchant Mill, Wire Rod Mill and also a most modern Plate Mill. While input
to the BBM and subsequently to Merchant Mill and Wire Rod Mill comes from the
Twin Hearth Furnaces, the Rail & Structural Mill and Plate mill roll long and flat
products respectively from continuously cast blooms and slabs only. The total
length of rails rolled at Bhilai so far would circumvent the globe more than 4.5
times.
To back this up, we have the Ore Handling Plant, three Sintering Plants - of
which one is most modern, two captive Power Plants with a generating capacity
of 110 MW, two Oxygen Plants, Engineering Shops, Machine Shops and a host of
other supporting agencies giving Bhilai a lot of self-sufficiency in fulfilling the
rigorous demands of an integrated steel plant. Power Plant No.2 of 74 MW
capacity has been divested to a 50:50 SAIL/NTPC joint venture company.

7. The plant has undertaken massive modernization and expansion plan to produce
7.5 MT of hot metal by the year 2010.
HUMAN PROFILE
More than the machinery and processes, it is the men i.e. the engineers,
technicians, skilled and unskilled workers behind them that constitute the flesh
and blood of this steel plant.
Bhilai at present has around 34000 persons to run this pulsating giant. The
culture which has today become the hallmark of Bhilai is a result oriented
approach to work. It is their effective and co-operative working relationship
nurtured in a spirit of dedication and enthusiasm that has shaped Bhilai's image
today.
Adjoining the plant, a modern township - Bhilai Nagar, having the spaciousness
of a village and the cleanliness of a modern town is spread - over in 17 self
sufficient sectors with schools, markets, parks and other facilities.
Free Medical aid is given to all the employees and their dependents through a
network of health centres, dispensaries and hospitals. Medical facilities are
extended to retired employees & their spouses also.
The Education Department runs a number of higher secondary, middle, primary,
and pre-primary schools in Bhilai and also in the mines townships at Rajhara,
Nandini and Hirri.

8. ELECTRICAL REPAIR SHOP
Fig. Electrical Repair Shop
Looking towards any integrated steel plant scenario, the importance of an
Electrical Repair Shop can be very well visualized. It is one of the major service
shops which carry out repair of all electrical machines used inside the plant;
there are around 42000 electrical machines installed and running continuously
years together, in different processes of production, in Bhilai Steel Plant. General
maintenance like cleaning, greasing and physical inspection / check-up is done
by concerned shops where the machines are used. All major repairs like winding
repairs, mechanical repairs, modification in existing winding and periodic
overhauling etc. are being attended by Electrical Repair Shop either at site or at
ERS.
SCOPE OF WORK:
Electrical Repair Shop carries out repairs of motors,
generators, welding and control transformers, load lifting magnets, brake &
control coils of all types and capacities. It also manufactures a large number of
spare parts like contact materials, switches, components, bus bar and various
other electrical spare parts. Repair of load lifting magnets, welding transformers,
control transformers and rectifiers are carried out in magnet and transformer
repair shop (MTRS). MTRS also fabricates load lifting magnets of all varieties
using all in-house technology and resources including the design concept.
Traction motors and roll table motors from various Rolling Mills are overhauled in
Motors Overhauling and Repair Section (MORS) adjacent to MTRS.
PRODUCTION TARGETS:

9. E.R.S. on an average repairs 380 motors and generators,
manufactures/reclaims 535 nos. coils, repairs 17nos. load lifting magnets,
28nos. welding & control transformers per month. The monthly repair work in
case of motors and generators is given below in tabular form:
Some repair work is off loaded to outside agencies strictly on need basis, such
as core staggering, shaft change etc. for which repair facilities are not available
in ERS. Such repairs are limited in number (5 - 10 machines per year) and
applicable for big size and critical machines only.
MAN POWER:
ERS has a present manning of 234 non-executives and 13
executives of various grades. The shop is headed by DGM (E - ERS).
METHODOLOGY AND PROCESS FLOW:
Electrical machines are received from
various shops within plant, township areas, mines etc. along with its work order.
The work order contains the machine specification, its defect, previous job no.
and any specific requirement by the concerned department. Receipt & Issue
section (R&I) of ERS allots a job No. to each and every machine after proper
verification of the machine and its accompanying work order. The number is
painted on motor body and on all dismantleable parts. Thereafter the machine is
traced in ERS by that job number only. R&I section intimates to the concerned
sections through internal job register for repair of these machines or
components on day to day basis. To facilitate a systematic repair process the
shop is divided into different sections. These are:
1. R & I section
2. Computer section
3. Assembly and dismantling section
4. Winding section
5. Varnishing section
6. Testing section
7. Machine section
8. Spare parts manufacturing section

10. 9. Commutator repair section
10. Stores
11. Shop maintenance
12. Magnet & Transformer Repair Shop (MTRS)
13. Motor Overhauling and Repair Section (MORS)
ASSEMBLY & DISMANTLING SECTION:
Machines after dismantling are subjected
to preliminary check-up (Meggering and visual inspection). Accordingly these
components are sent to various sections on the basis of the repair work
involved. The healthy components are cleaned thoroughly and varnished in
varnishing section before being sent to testing section for preliminary test. These
components after testing are sent to respective assembly sections. The defective
components are sent to respective winding sections for repair / rewinding. The
assembly section takes those componentsof a machine for assembly which are
ready in all respects. Before assembly the components are thoroughly checked
to ensure whether all the repairs as mentioned in work order or as noticed by
assembly group are carried out or not. In case there is some omission, it is sent
to concerned section for further repair. All the windings are meggered to ensure
healthy IR value and continuity in winding. All the mechanical parts like end
covers, grease cups, bearings and their seatings are thoroughly cleaned before
final assembly. The assembly group also conducts certain post assembly checks
like freeness of rotor / armature, proper brush seating, tightness of rocker arms
and their corresponding assembly in case D.C.Machine, Meggering of
components, tightness of body bolts etc. before sending the jobs to testing
section for final testing.
WINDING SECTION:
Winding sections take up jobs either for rewinding or
partial repair. Before rewinding the soundness of core laminations is ensured by
"Flux Test". In case there is some abnormal heating of at some patches as
detected by "Flux Test" core repair is done to rectify it. Componentsare
recommended for rewinding unless soundness of core is ensured. The
components rewound / partially repaired are subjected to a set of tests as per
norms like high voltage test, current balance test, magnetic field test, checking
of all joints etc. for their soundness. These components, if passed through all
these standard tests are preheated, varnished and cured in furnace for a period
of 16 - 18 hours. Finally covering varnish is applied on these windings before
sending to respective assembly sections.
TESTING SECTION:

11. Fig. To show high voltage tester
Testing section conducts the following tests on all repaired machines on no
load at ERS besides conducting a set of tests on all machine components in
intermediate stages. These include:
AC SQUIRREL CAGE INDUCTION MOTOR:
Fig. To show squirrel cage rotors
Meggering, physical
inspection, HV test, no load running test (for 30 minutes), inter turn insulation
test (for 2 minutes)

12. AC SLIP RING MOTOR:
Meggering, physical inspection, HV test, ratio test
no load running test (for 30 minutes), inter turn insulation test (for 2 minutes),
supply to rotor.
D.C. MOTOR: Meggering, physical inspection, no load running test (for 30
minutes), over speed running test (120% of rated speed for 3 minutes), load
test (for 5 minutes). All these machines during “No Load Test " should draw
current as per prescribed norms and there should not be any abnormal heating,
vibration, sound etc. so as to be declared fit for despatch. D.C. machines in
addition to these should run sparkless and speed fall should be within reasonable
limits on load condition. Testing group after ascertaining all quality checks
despatches these machines to R & I.
MAGNET & TRANSFORMER REPAIR SECTION (MTRS):
MTRS repairs all load lifting
magnets, control transformers, welding transformers, rectifiers. It also fabricates
load lifting magnets of all varieties. The design of these magnets is developed by
planning & technical department (P.T.D.) with the development of drawing for
shell, centre pole, coil and non magnetic plates. The magnet shell is cast from
high permeability steel. Centre pole is an integral part of the shell and the pole
shoe is bolted to the shell. Shell and centre pole shoe have been cast in Foundry
shop and machined to dimension in machine shop - I as per the drawing
developed by P.T.D. These machine shells are tested by various ultrasound
testing techniques and found acceptable. After insulating and curing the shell,
coils are assembled into the shell with suitable inter coil insulation. Heat
resistant compound is poured into the shell to make all the internals monolithic.
These magnets after fixing nonmagnetic plate and providing terminal boxes are
delivered to shops after testing on no-load and load test at M.T.R.S. These
magnets are working satisfactorily at various shops.
MOTOR OVERHAULING & REPAIR SECTION (MORS):
MORS does
overhauling of traction motors and roll table motors received from various rolling
mills.
MAIN EQUIPMENTS INSTALLED AT ERS
1. Three E.O.T. Cranes 5 Ton, 15/3 Ton and 10 Ton (Reclamation)
2. Four Cantilever cranes (1 ton each)
3. Two induction regulators
4. One H.T. & L.T. D.O.L. starter
5. One load testing equipment (Dynamometer - up to 50 kW.)

13. 6. One load testing equipment (Load generating system - 150 kW, 1000 r.p.m.)
7. Nine numbers coil winding machines
8. Six numbers lathes of various sizes
9. Five numbers furnaces
10. One bandaging machine
11. One balancing machine
12. One shaping machine
13. One stator coil forming machine
14. One coil cutting and pulling machine
15. Five telphers, 1 Ton each
16. Four drilling machines
17. Three grinding machines
18. One punching machine
MAIN EQUIPMENTS INSTALLED AT MTRS
1. One 20 Ton E.O.T. crane
2. One coil making machine
3. One furnace
4. One grinding machine
MAIN EQUIPMENTS INSTALLED AT MORS
1. One 20 Ton E.O.T. crane
2. One Hydraulic press
3. One bandaging machine
4. One lathe
5. One furnace
PROCESS FLOW OF ERS

15. ELECTROMAGNETS
An electromagnet is a type of magnet in which the magnetic field is produced
by an electric current. The magnetic field disappears when the current is turned
off. Electromagnets usually consist of a large number of closely spaced turns of
wire that create the magnetic field. The wire turns are often wound around a
magnetic core made from a ferromagnetic or ferrimagnetic material such as
iron; the magnetic core concentrates the magnetic flux and makes a more
powerful magnet.
The main advantage of an electromagnet over a permanent magnet is that the
magnetic field can be quickly changed by controlling the amount of electric
current in the winding. However, unlike a permanent magnet that needs no
power, an electromagnet requires a continuous supply of current to maintain the
magnetic field.
Electromagnets are widely used as components of other electrical devices, such
as motors, generators, relays, loudspeakers, hard disks, MRI machines, scientific
instruments, and magnetic separation equipment. Electromagnets are also
employed in industry for picking up and moving heavy iron objects such as scrap
iron and steel.
A simple electromagnet consisting of a coil of insulated wire wrapped around an
iron core. A core of ferromagnetic material like iron serves to increase the
magnetic field created. The strength of magnetic field generated is proportional
to the amount of current through the winding.
History
Sturgeon's electromagnet, 1824

16. One of Henry's electromagnets that could lift hundreds of pounds, 1830s
Danish scientist Hans Christian Ørsted discovered in 1820 that electric currents
create magnetic fields. British scientist William Sturgeon invented the
electromagnet in 1824.His first electromagnet was a horseshoe-shaped piece of
iron that was wrapped with about 18 turns of bare copper wire (insulated wire
didn't exist yet). The iron was varnished to insulate it from the windings. When a
current was passed through the coil, the iron became magnetized and attracted
other pieces of iron; when the current was stopped, it lost magnetization.
Sturgeon displayed its power by showing that although it only weighed seven
ounces (roughly 200 grams), it could lift nine pounds (roughly 4 kilos) when the
current of a single-cell battery was applied. However, Sturgeon's magnets were
weak because the uninsulated wire he used could only be wrapped in a single
spaced out layer around the core, limiting the number of turns.
Beginning in 1830, US scientist Joseph Henry systematically improved and
popularized the electromagnet.By using wire insulated by silk thread inspired by
Schweigger's use of insulated wire to make a galvanometer, he was able to wind
multiple layers of wire on cores, creating powerful magnets with thousands of
turns of wire, including one that could support 2,063 lb (936 kg). The first major
use for electromagnets was in telegraph sounders.
The magnetic domain theory of how ferromagnetic cores work was first proposed
in 1906 by French physicist Pierre-Ernest Weiss, and the detailed modern
quantum mechanical theory of ferromagnetism was worked out in the 1920s by
Werner Heisenberg, Lev Landau, Felix Bloch and others.

17. Uses of electromagnets
Industrial electromagnet lifting scrap iron, 1914
A portative electromagnet is one designed to just hold material in place; an
example is a lifting magnet. A tractive electromagnet applies a force and
moves something.
Electromagnets are very widely used in electric and electromechanical devices,
including:
 Motors and generators
 Transformers
 Relays, including reed relays originally used in telephone exchanges
 Electric bells and buzzers
 Loudspeakers and earphones
 Actuators
 Magnetic recording and data storage equipment: tape recorders, VCRs,
hard disks
 MRI machines
 Scientific equipment such as mass spectrometers
 Particle accelerators
 Magnetic locks
 Magnetic separation equipment, used for separating magnetic from
nonmagnetic material, for example separating ferrous metal from other
material in scrap.
 Industrial lifting magnets
 magnetic levitation
 Induction heating for cooking, manufacturing, and hyperthermia therapy

18. Laboratory electromagnet Magnet in a mass spectrometer
Physics
The magnetic field lines of a current-carrying loop of wire pass through the centre of the
loop, concentrating the field there
Current (I) through a wire produces a magnetic field (B). The field is oriented according to
the right-hand rule.
An electric current flowing in a wire creates a magnetic field around the wire,
due to Ampere's law. To concentrate the magnetic field, in an electromagnet the
wire is wound into a coil with many turns of wire lying side by side. The
magnetic field of all the turns of wire passes through the centre of the coil,
creating a strong magnetic field there. A coil forming the shape of a straight
tube (a helix) is called a solenoid.

19. The direction of the magnetic field through a coil of wire can be found from a
form of the right-hand rule. If the fingers of the right hand are curled around the
coil in the direction of current flow (conventional current, flow of positive charge)
through the windings, the thumb points in the direction of the field inside the
coil. The side of the magnet that the field lines emerge from is defined to be the
North Pole.
Much stronger magnetic fields can be produced if a "magnetic core" of a soft
ferromagnetic (or ferrimagnetic) material, such as iron, is placed inside the coil.
A core can increase the magnetic field to thousands of times the strength of the
field of the coil alone, due to the high magnetic permeability μ of the material.
This is called a ferromagnetic-core or iron-core electromagnet. However, not all
electromagnets use cores, and the very strongest electromagnets, such as
superconducting and the very high current electromagnets, cannot use them due
to saturation.
Side effects
There are several side effects which occur in electromagnets which must be provided for in
their design. These generally become more significant in larger electromagnets.
Ohmic heating
Large aluminium bus bars carrying current into the electromagnets at the
LNCMI (Laboratoire National des Champs Magnétiques Intenses) high
field laboratory.
The only power consumed in a DC electromagnet is due to the resistance of the
windings, and is dissipated as heat. Some large electromagnets require cooling
water circulating through pipes in the windings to carry off the waste heat.
Since the magnetic field is proportional to the product NI, the number of turns in
the windings N and the current I can be chosen to minimize heat losses, as long
as their product is constant. Since the power dissipation, P = I2
R, increases with
the square of the current but only increases approximately linearly with the
number of windings, the power lost in the windings can be minimized by

20. reducing I and increasing the number of turns N proportionally, or using thicker
wire to reduce the resistance. For example, halving I and doubling N halves the
power loss, as does doubling the area of the wire. In either case, increasing the
amount of wire reduces the ohmic losses. For this reason, electromagnets often
have a significant thickness of windings.
However, the limit to increasing N or lowering the resistance is that the windings
take up more room between the magnet's core pieces. If the area available for
the windings is filled up, more turns require going to a smaller diameter of wire,
which has higher resistance, which cancels the advantage of using more turns.
So in large magnets there is a minimum amount of heat loss that can't be
reduced. This increases with the square of the magnetic flux B2
.
Inductive voltage spikes
An electromagnet has significant inductance, and resists changes in the current
through its windings. Any sudden changes in the winding current cause large
voltage spikes across the windings. This is because when the current through
the magnet is increased, such as when it is turned on, energy from the circuit
must be stored in the magnetic field. When it is turned off the energy in the field
is returned to the circuit.
If an ordinary switch is used to control the winding current, this can cause
sparks at the terminals of the switch. This doesn't occur when the magnet is
switched on, because the voltage is limited to the power supply voltage. But
when it is switched off, the energy in the magnetic field is suddenly returned to
the circuit, causing a large voltage spike and an arc across the switch contacts,
which can damage them. With small electromagnets a capacitor is often used
across the contacts, which reduces arcing by temporarily storing the current.
More often a diode is used to prevent voltage spikes by providing a path for the
current to recirculate through the winding until the energy is dissipated as heat.
The diode is connected across the winding, oriented so it is reverse-biased
during steady state operation and doesn't conduct. When the supply voltage is
removed, the voltage spike forward-biases the diode and the reactive current
continue to flow through the winding, through the diode and back into the
winding. A diode used in this way is called a fly back diode.
Large electromagnets are usually powered by variable current electronic power
supplies, controlled by a microprocessor, which prevent voltage spikes by
accomplishing current changes slowly, in gentle ramps. It may take several
minutes to energize or deenergize a large magnet.
Lorentz forces
In powerful electromagnets, the magnetic field exerts a force on each turn of the
windings, due to the Lorentz force acting on the moving charges within the wire.
The Lorentz force is perpendicular to both the axis of the wire and the magnetic
field. It can be visualized as a pressure between the magnetic field lines,
pushing them apart. It has two effects on an electromagnet's windings:
 The field lines within the axis of the coil exert a radial force on each turn
of the windings, tending to push them outward in all directions. This
causes a tensile stress in the wire.

21.  The leakage field lines between each turn of the coil exert a repulsive
force between adjacent turns, tending to push them apart.
The Lorentz forces increase with B2
. In large electromagnets the windings must
be firmly clamped in place, to prevent motion on power-up and power-down
from causing metal fatigue in the windings. In the Bitter design, above, used in
very high field research magnets, the windings are constructed as flat disks to
resist the radial forces, and clamped in an axial direction to resist the axial ones.
Core losses
In alternating current (AC) electromagnets, used in transformers, inductors, and
AC motors and generators, the magnetic field is constantly changing. This
causes energy losses in their magnetic cores that are dissipated as heat in the
core. The losses stem from two processes:
 Eddy currents: From Faraday's law of induction, the changing magnetic
field induces circulating electric currents inside nearby conductors, called
eddy currents. The energy in these currents is dissipated as heat in the
electrical resistance of the conductor, so they are a cause of energy loss.
Since the magnet's iron core is conductive, and most of the magnetic field
is concentrated there, eddy currents in the core are the major problem.
Eddy currents are closed loops of current that flow in planes perpendicular
to the magnetic field. The energy dissipated is proportional to the area
enclosed by the loop. To prevent them, the cores of AC electromagnets
are made of stacks of thin steel sheets, or laminations, oriented parallel to
the magnetic field, with an insulating coating on the surface. The
insulation layers prevent eddy current from flowing between the sheets.
Any remaining eddy currents must flow within the cross section of each
individual lamination, which reduces losses greatly. Another alternative is
to use a ferrite core, which is a non-conductor.
 Hysteresis losses: Reversing the direction of magnetization of the
magnetic domains in the core material each cycle causes energy loss,
because of the coercivity of the material. These losses are called
hysteresis. The energy lost per cycle is proportional to the area of the
hysteresis loop in the BH graph. To minimize this loss, magnetic cores
used in transformers and other AC electromagnets are made of "soft" low
coercivity materials, such as silicon steel or soft ferrite
ROUND ELECTROMAGNETS
Round electro magnets are known for their applicability in various fields. The
electro magnets are designed in such a manner to develop deep penetrating
electromagnetic field to lift scrap and other diversified forms of ferrous
materials. Circular lifting electro magnets are used in transporting steel blocks,
pigs and scrap in scrap yards, ports and foundries. They also crush clinker in
skull cracker ball operations.

22. Electromagnets in Bhilai steel Plant are operated on 220V DC supply. The cover
of round magnets is made up of stainless steel (non magnetic) plate. So it
cannot be cut by normal welding. To open the cover either we have to use a
lathe machine or Gouging arc. Gouging arc is generated by using a carbon rod at
a current of 2000A and at high pressure (80-100psi). The maximum strength of
the magnetic field is at the centre pole (made up of cast iron and attached to the
outer frame).
Stainless Steel plate used as a covering for the electromagnet.
How to Distinguish between Underwater and surface
magnets?
Underwater Magnets:
Single wire comes out from the terminal box (highly
sealed to keep it away from water). Another distinguishing feature i the
provision of a hut adjacent to the terminal box to protect the wire from wear and
tear.
Surface Magnets:
Two wires come out from the terminal box.
Bulldog is used to keep the wire from terminal box in fixed position.

23. The magnets designed for underwater use but absorb moisture and will have
more life if used as a surface magnet is marked as Striker.
Terminal Box:
The coils inside the magnet are connected in series. The starting point of the
first coil and the ending point of the last coil are put through to the terminal to
give them supply voltage. Testing of electromagnet is done through the terminal
box. Megger is used to measure the voltage drop while resistance is measured
by using a multimeter. The terminal box can be seen in the image below. It will
be divided in to two compartments using a Texolite sheet. The hut for protecting
the supplying wire can also be seen adjacent to the terminal box.
Fig. To show Terminal Box along with Hut.
Coils
An electromagnet can be constructed by using 4, 6 or 8 coils. 4 coil
electromagnets are common but one with 8 coils is rare. The thickness of the
coil varies according to the number of coils to be placed in the magnetic cell. The
coils are made up of insulated copper strips.

24. Fig. To show cross-sectional view of a coil.
Insulation
(1) Paramite sheet:
The thickness of paramite sheet varies from 1.6 to
3.2mm. It can absorb moisture.
Fig. To show rolled up paramite sheet
(2) Mica Sheet:
It comes in the form of square shaped sheets. 4 mica
sheets are used to cover the coil periphery once.

25. Paramite and mica sheets along with varnish are used to provide insulation
between the coils.
Fig. To show a part of mica sheet
(3) Glass Sheets:
Fig: To show a glass sheet
Glass sheets are heat and fire proof and do not
absorb moisture. These are used to provide the in insulation between the
centre pole and the coils. 2 layers of glass sheet are fitted between pole and
coils. Space between the glass sheets is filled with paramite and mica. If
space is left then it is again filled with glass sheets by applying force so that
the coils get fixed.
Compounds
(1) SR (Silicone rubber) Compound:
Structure is just like normal
rubber. It is formed by mixing liquid and hardener along with
continuous stirring. The mixture becomes solid after leaving it

26. undisturbed for 3 to 4 hours. It is used to provide the insulation
between the coil and the magnetic cell.
(2) HRC (High Rupturing Capacity) Compound:
The liquid and
hardener are mixed in the ratio of 4:1 (5l hardener for 20l HRC). It is
very hard and possesses high strength.
SR Compound is more commonly used because when the magnet
comes for repairing, SR Compound is easy to dismantle whereas if HRC
compound is used, the magnet is first heated in the furnace and then
only the compound can be removed.
Anabond 901B:
Part A: Resin
Part B: Catalyst
Part A and Part B are thoroughly mixed in the ratio of 100:1.25 and
stirred well.
Safe Handling Method: Provide ventilation to control vapour exposure within
inhalation guidelines when handling at elevated temperature.
Anabond Two Part System
Storage: Catalyst is highly moisture sensitive. Store in a cool, dry place away
from moisture.
Texolite Sheet:
It is also called chemical wood. From outside surface looks
smooth like tiles and its texture is wooden from the sides. It is used to separate
the two columns in the terminal box.

27. Texolite Sheet
Metrosil:
It is a device connected in parallel to the supply wires in the terminal
box. It is used to tackle the sudden surges in power supply when all other
equipments are turned off at once. It is generally a Metal Oxide Varistor (MOV).
The resistance of a varistor varies according to the voltage across its terminals.
When the voltage across its terminals is high, its resistance decreases to provide
an alternative path for the excess current to flow thus saving the coils of the
electromagnet from burning out.
Metrosil (Surge Suppressor)
RECTANGULAR MAGNETS

28. To show a Rectangular Electromagnet
Most of the description for round and rectangular electromagnets is same. The
key differences are:
(1) The shape is different from that of round magnets. The coils used are
rectangular in shape instead of round.
(2) Basically divided in to three types depending upon the manufacturer
and the shape.
(3) Out of the three types only the box type electromagnet uses Metrosil
to protect its thin copper strips from burning out.
(4) The total resistance of coils in case of round electromagnets is around
2.8-3.2 mega ohms. In case of rectangular magnets the total
resistance of coils is high (between 7-8 mega ohms).
(5) Rectangular electromagnets are used to lift the finished products in
billet mill, merchant mill etc.

29. Rectangular Magnet to be repaired
Complete Repairing Process for Load Lifting Electromagnet
The complete procedure basically consists of External supervision, dismantling
and assembly. Procedures are same for most of the lifting magnets the only
difference is that the terminal box is waterproof in case of underwater magnets.
Procedure for magnet repairing:
Supervision
1. Identify the job number of the magnet which is to be repaired.
2. Using cranes put the magnet in the repair section carefully & open it using
proper tools.
3. External inspection is done by looking at outer terminal, magnetic &
nonmagnetic body of the magnet.
4. Record the fault present in the magnet & highlight it by using a chalk.
5. Test the insulation resistance using multimeter. If resistance is not
appropriate then the magnet will be opened for further repairing process
Dismantle
1. First the base of the electromagnet is detached by using gas welding.
2. Silicon compound is removed from the terminal box without damaging the
metrosil.

30. 3. Check the metrosil and the wires in the terminal box for any damage.
The remaining electromagnet is inverted using overhead crane.
4. To remove the stainless steel plate, Gouging arc is used.
5. Insulation sheets are removed and coils are taken out one by one from the
cell.
6. Resistance and voltage drop across each coil is measured using multimeter
and megger respectively.
Assembly
1. After dismantling, the inner part of the cell is cleaned using a wire brush and
checked for any damage to the body.
2. Bottom of the cell is insulated by double layers of mica sheet & double
layers of 1.6mm paramite sheet or 3.2 mm single Permanente sheet
3. One more layer of mica sheet is provided & thermosetting varnish is done
over the layer.
4. Centre pole is insulated & rolled with mica and glass sheet up to appropriate
height & then it is varnished.
5. After the insulation, varnishing is done to remove the moisture & allowed to
settle by putting weight on it.
Weights that are used after varnishing.
6. Heating is done in heating furnace for 24 hours at 120o
C.
7. Once it is done then it is allowed to cool & weights are removed.
8. Good quality coils are used. It is cleaned & insulation is removed for brazing.
9. Coils are in series, number of coils represents the ampere turn & magnetic
field capability of the magnet.

31. 10. Red varnish is used on both sides of coil winding for insulation purpose.
11.Brazing is done to take out lead from copper coil. T.C.I cleaning agent is
used & then rolled with glass tape.
12.To tighten the coils, mica sheets and glass sheets are filled into the gaps
between the coil & centre pole. SR or HRC compound is used to fill the gap
between the cell & the coils.
13.Jumper is taken out from the coil for series coil connection.
For putting another coil in series same layers of insulation are provided with
same procedure.

32. Conclusion
This project is made on the basis of study & observation of different types of
magnets and their properties. All the parameters are based on SAIL IPSS
standards. The project is only for study purpose in colleges.