Saturday, 18 January 2020

What is AC Servomotor? and What is Universal Motor or AC series motor?

AC Servomotor:-                                                                                                                     

AC Servomotor
AC Servomotor


The main parts in construction of AC Servomotor are stator and rotor.

  • The a.c servo motor is basically consists of stator and rotor. The stator carries two winding.   
  • One winding is called as main winding or reference winding is excited by constant voltage source.
  • And other winding is called as control winding is excited by variable control voltage. 
  • The winding are 90 away from each other and control voltage is 90 out of phase with respect to the voltage applied to main winding.
  • This necessary to obtain rotating magnetic field.

  •  Rotor is generally two types 

  1. Squirrel cage rotor 
  2. Drag cup type rotor.

Operating principle:-

1. The operating principle of AC servo motor is same as that of normal three phase induction motor.
2. The control voltage is applied to control winding and the voltage applied to the main winding are 90 out of phase.
3. Hence flux produced by current through the control winding is also out of phase with respect to flux produced by the main winding.
4. The resultant flux in the air gap is hence rotating nature is called as rotating magnetic field.
5. The rotor is stationary at start. But rotating magnetic field rotate over surface of the rotor, and EMF get induced in rotor.
6. This  EMF circulate the current through the rotor.
7. The rotor current produced its own flux called as rotor flux.
8. This flux inter acts with the rotating magnetic field, produced a torque on rotor and rotor start rotating.

Application of Ac Servo Motor:-

  • Machine tool.
  • Robotics.
  • Process controller.
  • Self-balancing recorder.

Universal motor or A.C. series motor:-

Universal Motor
Universal Motor

There is small capacity series motor which can be operated on D.C supply or single phase A.C supply  of same voltage with similar characteristics, called as “ universal motor “

The general construction of such motor is similar to that of A.C  series motor.
It is manufactured in two types:-
i.                    Non- compensated (Low H.P).
ii.                  Compensated type (High H.P).

Non- compensated type universal motor has 2 poles having entire magnetic path as laminated.

 Reversal of rotation of universal motor is obtained by changing connection of armature winding. 
As well as speed reversal is obtained by changing connection of field winding.


Universal motor work’s on principle of “when a current carrying conductor is placed in a magnetic field, the conductor experience a mechanical force” the direction of this force is given by Fleming’s left hand rule.
1. When motor is connected to an A.C. supply, the same alternating current which flows through armature and field winding.

2. The field winding produced alternating flux (ϕ) that reacts with current flowing through in armature which produced a torque.

3. Since both armature and flux reverse simultaneously, the torque always same direction.

4. It may note that no rotating magnetic field produced in this types of motor.

  • High speed vacuum cleaner.
  • Sewing machine.
  • Food processors.
  • Mixer and grinder.
  • Drilling machine.

Reversal of rotation:
  • The reversal of rotation of universal motor is carried out by changing one of winding (armature or field winding) connection.
  •  Reversal of rotation of universal motor is obtained by changing connection of armature winding as well as speed revers al is obtained by changing connection of field winding.


Friday, 17 January 2020

AC Distribution System- Radial System, Ring main System, Interconnected System

AC Distribution System

         AC distribution system is defined as the part of power system which distribute electric power for local use.

AC Distribution System
AC Distribution System 

In distribution system it consist of 3 main components.

1. Feeder 
2. Distributor
3. Service mains


  • A feeder is a conductor which connect the substation to the area where power is to be distributed i.e. distributor conductor. 
  • No tapping are take from the feeder therefore current in it remains same  through out. 
  • A feeder is design from the point of view of its current  carrying capacity.


  • A distributor is a conductor from which tapping are taken for supply to the customer. 
  • The current flowing through distributor is not constant 
  • While designing distributor conductor voltage drop is main consideration.

 Service Main

It is a generally a small cable which connect the distributor to the consumer end.

Classification of AC distribution system 

According to the nature of current 
1. AC (Alternating Current)
2. DC (Direct Current)

According to construction 
1. Overhead 
2. Underground 

According to scheme of connection 
1. Radial system 
2. Ring main system 
3. Interconnected system 

1. Radial System 

Radial System
Radial System

  • In this system separate  feeders are taken from  single a substation and feed the distributor at one end only.
  • This system is employed only when power is generated at low voltage and substation is located at the center of load.

1) The end of the distributor nearest to the feeder will be heavily loaded.

2) The customer at the distant end of the distributor would be subjected to serious voltage fluctuation when the load on system changes. 

3) The consumer are dependent on single feeder and distributor and also single substations. Therefore any fault is occur supply will be cut off. No continuity of supply is maintained. 

2. Ring Main System 
Interconnected System
Ring main System 

  • In this system primary of all distribution transformer is connected to each other to form a loop. 
  • The main advantage of ring main system is the system is very reliable because each distribution via two feeder so less voltage fluctuation.

3. Interconnected system

Interconnected System
Interconnected System 

  • When the feeder ring or loop is energized by two or more than two substations or generating plant is called the interconnected system.
  • It increases service reliability. 
  • Substation and generating plant can share increasing demand on power system that is why only one plant or substation will not be under burden for supplying the maximum demand power. 

Requirement of Ideal Distribution System 

1. Proper Voltage 

  • One important requirement of distribution system is that voltage variation at customer terminal should be as low as possible 
  • Therefore a good distribution system should ensure that the voltage variation at a customer terminal are within permissible limit that is + - 6% 

2. Availability of power on demand 

  • Power must be available to the customer in any amount that they may require from time to time that means the distribution system must be capable of supplying load of customer.

 3. Reliability 

  • Modern industry is almost the dependent on electrical power for its operation therefore distribution system must be reliable which should maintain continuity of power supply.

Thursday, 16 January 2020

High Voltage DC Transmission System- Advantages, Disadvantages, Applications

High Voltage DC Transmission System

Layout of HVDC Transmission System
Layout of HVDC Transmission System 

Advantages of HVDC Transmission

1) Cheaper in cost
2) Line losses are less.
3) No skin effect due to absence of inductance.
4) Less corona losses.
5) Greater reliability.
6) Greater transmission efficiency. HVDC system requires only one or two conductors and because of absence of skin effect the effect of resist of conductor is less. So due to lower losses it has greater efficiency.
7) Greater voltage regulation. Due to absence of inductive reactance  voltage drop voltage drop in the line is less. Hence voltage regulation is greater.
8) Absence of charging current.
9) There is no limitations of line loading.
10) Lower short circuit current.
11)Independent control is possible.
12) Rapid change of energy flow can be achieved.

Disadvantages of HVDC Transmission

1) Power can not be generated in DC form.
2) Voltage can not be step up or step down.
3) The design of switches or circuit breakers is difficult in DC circuit.
4) The converter station can produce harmonics which affect the stability of system.
5) The cost of high voltage DC system is more below 75km of length.

Applications of High Voltage Transmission System

Long distance high power transmission.

High voltage transmission system is preferred that is above 750km or 500 km or more than 500km.

Underground or under water transmission-
Due to the absence of charging current and lower dielectric losses HVDC cable can be used for underground or under water transmission.

Back to Back connection-   
For back to back connection of AC or DC the generally high voltage transmission system is used.

For conversion of frequency for inter grid connection.

Multi terminal HVDC system is used for inter connecting 3 or more than 3 phase supply. 


Wednesday, 15 January 2020

Different Types of HVDC Links- Monopolar HVDC System,Bipolar HVDC System, Homopolar HVDC System.

High Voltage DC Transmission System


1) As transmission voltage increases current decreases therefore cross section of conductor reduces.
2) As cross section of conductor decreases its weight also decreases.
3) If weight of conductor decreases the design of tower becomes lighter in weight.
4) Transmission cost per kilometer decreases.
5) As voltage increases current reduces, therefore transmission line losses also reduces.
6) Transmission efficiency increases because of reduction in line losses.
7) Voltage regulation increases because of reduction in voltage drop.
8) Increases transmission capacity of line.
9) Increases surge impedance loading.
10) Possibility of interconnection of power system.
11) Flexibility of future load system increases.
12) Huge amount of power transmitted for long distance. 

High Voltage DC transmission system

  • The generating voltage is in the form of AC that is in 11KV this voltage is stepped up with the help of step up transformer. 
  • The increased voltage is given to converter station. The converter station consists of SCR (silicon controlled rectifier) and filter and other equipment.
  • The converter converts AC in DC power with the help of of SCR. 
  • Then DC power is transmitted through line known as HVDC (High Voltage DC) line after transmission of DC power it is again converted into AC power at receiving end with the help of inverter. Then the  voltage is decreases by step down transformer and ac power utilize in load station.

Classification of AC DC system

1. Monopolar HVDC system

2. Bipolar HVDC system

3. Homopolar HVDC system

1. Monopolar HVDC system

Monopolar HVDC System
Monopolar HVDC System

  • This system has only one pole is used and return path is provided through permanent earth or sea. Generally monopolar HVDC line is operated at negative polarity for transmission with respect to earth by using negative polarity for transmission we can reduce radio interference. 
  • This system is used for low power transmission up to 250 MV but it is economical because only one conductor is used for transmission so losses are reduces and cost is save.
  • The earth electrode are design for continuous flow of leakage current or fault current.

2. Bipolar HVDC system

Bipolar HVDC System
Bipolar HVDC System

  • This system is most widely used for overhead long distance HVDC transmission it is also called as back to back hd dc system. 
  • In this link two conductors are used it is operating with negative polarity and other is with positive polarity. 
  • There are two conductor which having equal  rating and connected in series the junction between converter may be grounded at one end or both the ends when it is grounded at both end each for operate independently.
  • The rated voltage of bipolar link is expressed as 500KV.

3. Homopolar HVDC system

  • Homopolar has to conductor used with having polarity normally positive polarity is used for transmission and negative polarity is always operated at grounded return conductor 
  • In case of faulty condition power can we transfer by using another set of conductor such a scheme is complicated therefore mostly bipolar HVDC link preferred.


Tuesday, 14 January 2020

What is Corona Effect? Its Advantages and Disadvantages,

Corona Effect

Corona Effect

Corona Effect

When an alternating potential difference is applied across two conductors whose spacing is large as compared to there diameter there is a no effect in change in atoms air surrounding the conductor.

When applied voltage is  exceeds a certain value then conductors are surrounded by faint violate glow and hissing noise and ozone gas called Corona.
The phenomenon of violate glow, hissing noise and ozone gas in an overhead transmission line called corona.

Theory of Corona Formation 

  • Some ionization is always present in air due to cosmic ray's, radioactivity and ultraviolet radiation under normal condition. 
  • The air around the conductor contains some free electrons and positive ions. 
  • When potential difference is applied potential gradient is set up in the air which will have maximum at the conductor surface under the influence of potential gradient, the existing free electrons acquire greater velocity. 
  • The greater the applied voltage greater, greater potential gradient and greater the velocity of electrons. 
  • When potential gradient reaches about 30Kv per cm the velocity acquire by free electrons is sufficient to strike the neutral molecule with enough force to dislodge more electron from it this process of ionization cumulative.
  • The result of this ionization is that either corona either corona is form or spark is takes place between the conductors.

Factors Affecting the Corona

In stormy weather the number of ions is more than normal and such a corona occurs at much less voltage as compare to fair weather.

Conductor Size
The rough and irregular surface will give rise to more corona thus a stranded conductors has irregular surface and hence give rise to more corona.

Spacing between conductors 
If the spacing between conductors made very large as compare to their diameter  there may not be any corona effect. 

Line voltage
If the line voltage is low the corona corona effect is less because of less electrostatic stress. 

Advantages of Corona 

1) Due to corona formation the air surrounding of conductor becomes conducting and hence virtual diameter of conductor increases.

2) Corona reduces effect of transient produces sugar.

3) It reduces effect of high voltage travelling wave due to lightening. 

Disadvantages of Corona

1) Because of corona effect energy loss will occur in transmission line which affect efficiency of line.

2) Ozone gas is produces due to corona and may causes corrosion of conductor due to chemical action. 

3) Interference with neighboring communication line because current drawn by the line due to corona is no sinusoidal. 

Important terms related to corona

Critical disruptive voltage
It is minimum phase to neutral voltage at which corona occur.

Visual critical voltage 
It is minimum phase to neutral voltage at which corona glow will appear surrounding the conductor.

Power loss due to corona 

Monday, 13 January 2020

Transmission Line Parameters, Skin Effect, Proximity Effect, Ferranti Effect, Transposition of Conductor.

Transmission Line Parameters 

  • The transmission line has different parameters and constant along with the length of line. 
  • Generally this parameters resistance, inductance, and capacitance. 
  • Such parameters affects on performance and efficiency of transmission line .
Transmission Line Parameters
Transmission Line Parameters

Concept of  R, L, and C in Transmission line 


It is opposition to flow of current in transmission line. The resistance is distributed along the length of line.


When ac current flow in the line change in flux occurs which links the conductor due to this flux leakage conductor passes as inductance. 


When two conductors are separated by an insulating material then it called capacitance. As any two conductors of transmission line are separated which acts as insulation therefore capacitance exists between any two lines. 

Effect of Resistance in 

1) Transmission Line Efficiency

  • In case of transmission line receiving end power is always less than sending end power due to current losses and voltage drop occurs in line hence we get less power at receiving ends. 
2) Voltage Regulation
  • Voltage regulation is defined as the ration of change in voltage at sending end to receiving end or from no load to full load.
  • Because of line parameters receiving end voltage is always less than sending end voltage.

Effect of Inductance 

Skin Effect 
  • The tenancy of alternating current to concentrate near the conductor is known as skin effect.
  • Due to the skin effect the effective area of cross section of conductor through which current flow is reduce therefore the resistance of conductor is slightly increases when ac current flows.
  • A solid conductor when used for transmission current is flow through all the parts i.e inner filament of conductor. Therefore flux linkage takes place at center. There is more effect of magnetic flux and hence have larger inductance than surface of conductor.
  • If we move from center towards the surface the effect of inductance goes decreases and due to this current flows near the surfaces of conductor only.
  • This crowding of  current near conductor surface is skin effect.
  • It depends on 
1) Nature of material
2) Diameter of conductor
3)Supply frequency
4)Shape of conductor 

Proximity Effect
Proximity Effect
Proximity Effect 

  • Suppose the conductor of transmission line are separated by certain distance. When the conductor carries current then the flux is link with another conductor i.e there will be flux linkage of both conductors.
  • When conductor A carries current its flux will link conductor B. If both are conductors carries current in opposite direction due to its flux linkage the current through both the conductors will try to flow only for shaded portion of  conductor.
  • If both conductors carries current in same direction due to its flux linkage current will only flow outer cross sectional area of  conductor. This effect is known as proximity effect.
  • It can be reduced by increasing distance between two conductors and reducing current flow through conductors.

Ferranti effect

Ferranti Effect
Ferranti Effect

  • When along with transmission line is operated under no load or light load condition then receiving end voltage is greater than sending end voltage. 
  • Due to capacitive reactance of the system current flowing through to line is in leading PF this charging current produces voltage drop in reactance which in phase opposition to receiving end voltage hence vr^vs this effect is known as ferranti effect.
Transposition of conductor

Transposition Of Conductor
Transposition Of Conductor
When three phase line conductors are not equidistant from each other the conductor spacing is
said to be unsymmetrical under such Condition flux linkage and inductance of each phase are
not same.The different inductance in each phase result in unequal voltage drop  in 3 phase. Even
though the current in the conductor in three phase are equal. Therefore the VR will not be same
for all phases in order that voltage drop are equal in all conductors. we generally interchange the
position of conductor at regular interval along the length of lines of that each conductor take
original position of another conductor over equal distance such an exchange of position is

Friday, 10 January 2020

Transmission Line Components- Conductor, Support, Insulator, Cross arm, Stay wire, V-guards, Bordered wire.

Transmission Line Components


  • Transmission and distribution are essential links between generating stations and costumers for transmission of power. 
  • Because of tremendous growth of industries the requirement of power has increases hence it become important that transmission and distribution of power carried out with minimum losses and disturbance. 
  • This is achieved by designing transmission and distribution system effectually, technically, strong and reliable which require low maintenance. 

Main Components Of Overhead Line:

Conductor- Conductors carry current from sending end to receiving end.

Support- Support which may pole or tower keeps the conductor at suitable level above the ground.

Insulator- Insulator which insulate conductor from the ground. 

Cross arm- Cross arm provide support to insulator. 

Stay wire- It is connected to the pole at some angle to resist literal forces or stress.

V-guards- It is provided below  bare overhead line running along or crosses public streets to make the line safe if it should break. 

Bordered wire- It is wrapped on a pole at a height 2.5 m from ground at least for 1 m. This prevents the claiming the to unauthorized person.

Overhead Conductors-

  • The conductor is one of important item of transmission system.  The most of the capital cost is invested for it. 
  • Therefore proper choice of material and size of the conductor it is very important. 
  • The conducting material  is use for transmission and distribution  should have following 
  • High electric conductivity.
  • High tensile strength in order to with stand mechanical stress. 
  • Low specific gravity so weight of conductor reduce. 
  • Low cost so that it can be use for long distance. 
  • It should be easily available. 
  • Copper Conductor
  • Aluminium Conductor 
  • Stranded Conductor 
  • ACSR Conductor (Aluminium Conductor Steel Reinforced)
  • AAAC Conductor (All Alloy Aluminium Conductor)

Line Support-

Requirement Of Line Support-
  • High mechanical strength to with stand the weight of conductor, insulator and wind.
  • Light in weight but without loss in mechanical strength.
  • It should have longer life.
  • It should be economical.
  • Easy accessibility for maintenance, transportation etc.   
Types of line support-
  • Wooden pole 
  • Steel pole 
  • RCC pole 
  • Steel tower


  • The overhead lines are supported by using different poles or towers 
  • The supporting structure in a such a way that  current from the conductor do not flow to the earth i.e line conductor must be properly insulated from the support this is achieved by securing line conductor from the support with the help of insulator.
Properties of Insulators-

1) It should have high mechanical strength in order to with stand weight of conductor and wind.

2) It should have high electric resistivity to avoid flow of leakage current.

3) It should have high relative permeability. In order to high dielectric strength.

4) The insulator material should be non porous, free from impurity and cracks otherwise permeability will be decreases. 

  • Pin type insulator
  • Suspension type insulator
  • Stay insulator
  • Strain insulator
  • Shackle insulator 
Causes Of Insulation Failure-

1) Poor mechanical strength-
Due to reduction of strength of insulation it may causes to failure.

2) Porosity-
The material used for insulator are made up of porcelain, glass such a materials has porosity property due to this it can be absorb moisture from atmosphere.

3)Internal Impurity- 
Due to this breakdown strength may get reduced of insulator.

4) Ageing-
Continues operation of insulator for long time periods may causes to increase flow of leakage current.

Due to lightning extra high voltage is appear across transmission  line if such voltage is more than its dielectric strength of insulator it may be permanently failed.

6) Uneven expansion and contraction- 
Insulator are manufactured by using different materials the coefficient of expansion and contraction is different due to this there will be possibility of cracking of insulator.

7) Wrong selection-
If 11Kv insulator are used for 22Kv or more then it cause to damage the insulator therefore insulator should be select according to voltage capacity.

8) Rough handling-
Due to rough handling of insulators during transportation and erection of line etc.


Thursday, 9 January 2020

Basic Transmission of Electrical Energy

Basic Transmission


  • The process by which large amount of power produced are transported over a long distance for eventual use by costumer.
  • Large amount of power is generated at generating station. And the power stations are located away from the populated areas where fuel water is available. This has shifted power station quite away from costumers and it has to supply to customer.
  • The convince of electric power from a power station to costumer premises is called electric supply system.

This network is divided into two parts-
  1. Transmission 
  2. Distribution
Single line diagram of Transmission and Distribution of electric supply

Transmission and Distribution of Electric Power
Transmission and Distribution of Electric Power

Generating Station:

  • Electric energy is generated by 3-ph alternator. 
  • The generation voltage is 11Kv or 6.6 Kv. 
  • This voltage is to low to transmission over ling distance therefore it is step-up 132Kv/220Kv/400Kv by using step-up transformer.

Primary Transmission:

  • The voltage which step-up transformer is transmitted to bulk power stations with is called receiving stations.
  • Generally the power transmission of primary is carried out by 132Kv/220Kv/400Kv by 3-ph  3 wire system with overhead system to the outer side of city. This form  primary Transmission.

Secondary Transmission:

  • The primary transmission terminated at a receiving station which usually lies at outside of the city.
  • At the receiving station the voltage is reduce to 33Kv or 66Kv by step-down transformer. 
  • This voltage is transmitted at 33Kv or 66kv by 3-Ph, 3 wire ovrhead system to various substation located at in the city.this form secondary transmission.

Primary Distribution:

  • A secondary transmission line terminate at the substation where voltage is reduced from 33Kv/11Kv.
  • Large industrial consumers are supply at primary distribution level of 33Kv while smaller industrial consumers are supply at 11Kv and further handling with there own substation.

Secondary Distribution:

  • The electric power from primary distribution line i.e 11Kv is deliver to distribution substation.
  • These substation are located near the consumer localities and step-down the voltage to 400v, 3Ph, 4 wire for secondary distribution.
  • The voltage between any 2 phase is 400v and any phase and neutral is 230v.
  • The single phase residential lighting load is connected between any phase and neutral where as 3 ph, 400v motor load is connected to 3 ph supply.

Classification of transmission Line 

1)According to voltage level
  • Primary Transmission 
  • Secondary Transmission
2)According to length of Transmission line 
  • Short Transmission 
  • Medium Transmission
  • Long Transmission
3)According to type of supply
  • AC Transmission
  • DC Transmission
4)According to method of construction 
  • Overhead Transmission
  • Underground Transmission

1) According to voltage level

The transmission line are classified according to two types
  • Primary transmission- is 132Kv/220Kv/400Kv . The power in bulk amount is from generation station is transmitted to step-up transformer.
  • Secondary transmission- is 66Kv/ 33Kv. The power from step-up transformer is transmitted to step-down transformer. Voltage is reduced to 33kv or 66Kv  by step down transformer.

2) According to length of transmission line

  • Short Transmission Line- When length of overhead transmission system is upto 50km and line voltage is lower than 20kv is called short transmission line.
  • Medium Transmission Line- When length of overhead transmission system is about 50km to 150km and line voltage is about 20Kv to 100Kv it is called medium transmission line.
  • Long Transmission Line- When the length of transmission system is more than 150km and voltage is more than 100kv it is called long transmission line.

3) According to method of construction

  • Overhead Transmission Line- In this method power is transmitted by overhead conductors. this overhead conductors are suspended freely in atoms by using supporting tower, insulator etc
  • Underground Transmission Line- In This method power is transmitted by underground cable consist of conductor at the center and surrounding tower, insulator etc.

Wednesday, 8 January 2020

Electric Conducting Material: High resistivity Or Low conductivity and Properties - Tungsten, Carbon, Nichrome, Manganin

Electric Conducting Material

High Resistivity Or Low Conductivity 
  • Materials having low conductivity or high resistivity  are very useful for some electrical engineering products and applications. 
  • To manufacture the filaments for incandescent lamp, heating elements for electric heaters and furnaces, space heaters and electric irons etc this materials are used.

Required Properties in High Resistivity or Low Conductivity Conducting Material
The properties are required in high resistivity or low conductivity conducting material are following-
  1. It should high resistivity.
  2. It should high melting point.
  3. High mechanical strength requires.
  4. It's ductility should high, so that can be drawn in the form of wire easily.
  5. It should high corrosion resistance mean free from oxidation.
  6. It' cost should be low.
  7. Long life or durable.
  8. High flexibility.

Some of Materials having High Resistivity or Low Conductivity are listed below

  1. Tungsten
  2. Carbon
  3. Nichrome or Brightray B
  4. Nichrome V or Brightray C
  5. Manganin


Tungsten Conductor
Tungsten Conductor

  • Tungsten is produced  from rare ores or from tungstic acids.
  • Some facts about tungsten are listed below-
  • It is very hard.
  • It's resistivity is twice to aluminum.
  • Tensile strength of tungsten is very high.
  • It can be drawn in the form of very thin wire.
  • In the presence of oxygen it oxidize very quickly. 
  • Can be used up to 2000 degree C in the atmosphere of inert gases (Nitrogen, Argon etc.) without oxidation.
  1. Specific weight : 20 gm/cm3
  2. Resistivity : 5.28 µΩ -cm
  3. Temperature coefficient of resistance : 0.005 / oC
  4. Melting point : 3410oC
  5. Boiling point : 5900oC
  6. Thermal coefficient of expansion: 4.44 × 10-9 / oC

Uses of Tungsten
  1. For incandescent lamp used as filament.
  2. Also used electrode in X- ray tubes.
  3. The great hardness, high melting and boiling points make it suitable for use as electrical contact material in certain applications. 
  4. It is having high resistance for destructive forces produces during operation of electrical contacts.

  • Carbon is widely used in electrical engineering. 
  • Electrical carbon materials are manufactured from graphite and other forms of carbon.


  1. Resistivity : 1000 - 7000 µΩ - cm
  2. Temperature coefficient of resistance : - 0.0002 to - 0.0008 /oC
  3. Melting point : 3500oC
  4. Specific gravity : 2.1gm /cm3

Uses of Carbon

Carbon is having following applications in electrical Engineering

  1. Making pressure sensitive resistors which are useful in automatic voltage regulators.
  2. Manufacturing the carbon brushes, that are used in DC machines. These carbon brushes improve the commutation as well as reduce the wear and tear.
  3. It also used for making filament of incandescent lamp.
  4. To make the electrical contacts.
  5. For making resistors.
  6. Also used for making battery cell elements.
  7. Used for electric furnaces as Carbon electrodes.
  8. Arc lighting and welding electrodes.
  9. Component for vacuum valves and tubes.
  10.  For makings parts for telecommunication equipment.

Nichrome or Brightray B
Composition of Nichrome or Brightray B
Ni=60% + Cr=15% + Fe= 25%

Properties of Nichrome or Brightray B

  1. Resistivity : 1.10 µΩ -cm
  2. Temperature coefficient of resistance : 0.0002 /oC
  3. Melting point : 1350oC
  4. Specific gravity : 8.24 gm /cm3
  5. High resistance to oxidation

Uses of Nichrome or Brightray B

  1. Used in making tubular heaters and electric irons.

Nichrome V or Brightray C

Composition of Nichrome V or Brightray C
Ni=80% + Cr=20%

Properties of Nichrome V or Brightray C

  1. Resistivity : 40 µΩ - cm
  2. Temperature coefficient of resistance : 0.0001 /oC
  3. Melting point : 1400oC
  4. Specific gravity : 8.4gm /cm3
  5. High resistance to oxidation

Uses of Nichrome V or Brightray C

  1. Used in making heating elements for electric heaters and furnaces.


Composition of Manganin
Cu=84% + Mn=12% + Ni=4%

Properties of Manganin

  1. Resistivity : 40 µΩ -cm
  2. Temperature coefficient of resistance : 0.0001 /oC
  3.  Melting point : 1400oC
  4. Specific gravity : 8.4gm /cm3
  5. High resistance to oxidation

Uses of Manganin

Manganin is having following applications in electrical Engineering.

  1. Used in making electric heating elements and in electric furnaces.
  2. As the manganin is having very low temperature coefficient of resistance, therefore it is used to make the standard resistances and in measuring instruments.


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