Tuesday, 30 January 2018

DC Motor Principle And Working!!

What is Principle Of DC Motor And How Its Work  ?!




DC Motor principle




An Electric Motor is a machine which converts electric energy into mechanical energy.



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Its action is based on the principle that a current-carrying conductor is placed in a magnetic fied, it experiences a mechanical force whose direction is given by "Fleming's Left-hand Rule " and whose magnitude is given by 
  • F = BIL Newton.

Where  B= magnetic field intensity          
              I= current flowing in the  conductor
              L=lenght of the conductor





  • Constructionally.,there is no basic difference between a d.c. generator and a DC Motor. 
  •  In fact, the same d.c. machine can be used interchangeably as a generator or as a motor. 
  • DC  Motors also like generators shunt wound or series wound or compound wound. 

.

In the figer a part of multipolar DC Motor shown. When its field magnets are excited and its armature conductors are supplied with current from the supply mains, they experience a force tending to rotate the armature.

  • Armature conductors under N-poles are assume to carry current downwards(crossed) and those under S-poles, to carry current upward(dots).
  • By applying fleming left hand rule the direction of the force on each conductors can be found. It is shown by small arrows placed above each conductor.  
It will be seen that each conductor can be found.  It will be seen that each conductor experiences a force F driving torque which sets the armature rotating.

It should be noted that the function of a commutator in the motor is the same as in the generator. By reversing current in each conductor as it passed from one pole to another, it help to develop a continuous and unidirectional torque.





Application of DC Motor

(1) shunt type DC Motor

*for driving constant speed line shafting
*Lathes
* centrifugal pumps
* Machine tools
*Blowers and fans
*Reciprocating pumps

(2) series type d.c motor

* For traction work i.e. Electric locomotives
*Rapid transut system
*Trolley, cars etc.
*Cranes and hoists
*Conveyors

(3) Comulative compound type DC Motor 

* For intermittent high torque loads
*For shears and punches
*Elevators
*Conveyors
*Heavy planers
*Rolling mills : Ice machine : Printing prosses : Air copressors





Questions Related To DC Motor:

1) define function of DC Motor???
Ans: An electric motor is a machine which converts electric energy into mechanical energy.

2) In d.c. motor conductor is experienced force by whose principle??
Ans: Fleming's Left-hand Rule

3)what is the function of commutator in d.c. motor??
Ans: the function of a commutator in the motor is the same as in the generator. By reversing current in each conductor as it passed from one pole to another, it help to develop a continuous and unidirectional torque.

4) In lathes machine which type of motor are uses???
Ans:shunt type d.c. motor

5)where the  series type d.c motor are used??
Ans:
* For traction work i.e. Electric locomotives
*Rapid transut system
*Trolley, cars etc.
*Cranes and hoists
*Conveyors

6)For intermittent high torque loads which motor are used?? 
Ans: Comulative compound type d.c. motor


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Sunday, 28 January 2018

Armature Reaction - An Effect Of Magnetic Field In The Electric Machines Armature!!

Armature Reaction - An Effect Of Magnetic Field In The Electric Machines Armature!! 




What is Armature Reaction In The Electrical Machine , What Is Effective The Armature Reaction To ElectricalMachine And How We Can Reduce It!!!  






By Armature Reaction is meant the effect of magnetic field set up by Armature current on the distribution of flux under main poles of a generator.




The Armature Magnetic field has two effects:
(1) It demagnetises or weakens the main flux and
(2) It cross-magnetises or distorts.




The first effect leads to reduce generated voltage and the second to the sparking at The Brushes.



These effect are well illustrated in figer.

  • Which show the flux distribution of a bipolar generator when there is no current in the Armature conductor. 
  • For convenience  only two poles have been considered through the following remarks apply to multipolar field as well .

  •  Morever the brushes are shown touching the armature conductor directly, although in practice, the touch commutator segment, 



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It is seen that

(a)  The flux is distributed symmetrically with respect to the polar axis which is the line joining the centers of NS poles.

(b)  The magnetic neutral axis or plane (M. N. A.)  coincides with the geometrical neutralaxis or plane(G.N.A.)



Magnetic neutral axis may be defain as the axis along which no e.m.f. is produced in the Armature conductors because they then move parallel to the lines of flux.

Or

M. N. A.  Is the axis which is perpendicular to the flux passing through the Armature.




Terms used in Armature reaction


(1) Geometrical Neutral Axis(GNA)

It is the axis midway between the opposite adjacent field poles and perlendicular to the centre lines of poles.

(2)Magnetic Neutral Axis (MNA)

MNA is the axis which perpendicular to the flux passing through the armature.
It is also define as the axis along which no emf is produce in the armature conductors.

(3)Leading Pole Tip(LPT)

It is the end of the pole which first comes in contact with armature in the direction of rotation by the armature conductors.

(4)Trailing Poles Tip(TPT)

It is the end of the pole which comes in contact later with the armature in the direction of rotation.



Some Questions Related To This Topic  :

1)The armature magnetic field has how manny effects and which???
Ans: Two
(1) It demagnetises or weakens the main flux and
(2) It cross-magnetises or distorts.

2) what is the full form of G. N. A???
Ans: geometrical neutralaxis or plane(G.N.A.)

3)define Magnetic neutral axis???
Ans: as the axis along which no e.m.f. is produced in the armature conductors because they then move parallel to the lines of flux.

4)what is Leading Pole Tip(LPT)???
Ans:It is the end of the pole which first comes in contact with armature in the direction of rotation by the armature conductors.

5) give the fullform of TPT and define TPT???
Ans:Trailing Poles Tip(TPT)
It is the end of the pole which comes in contact later with the armature in the direction of rotation.



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Wednesday, 24 January 2018

Commutator And Commutation - Mostly Needed Part In The DC Generator !!

Commutator And Commutation - Mostly Needed Part In The DC Generator  



Description About Commutator And Commutation Which is Mostly Useful Parts In DC Generator And How The Commutator Convert AC Current DC Current Using Commutation Process. 







We all know that The Current induced in Armature conductors of a d.c. generator are alternating. 





To make their flow unidirectional in the external circuit, we need a Commutator.


Over, these Current Flow in one direction when armature conductore are under N-pole and in the opposite direction when they are under S-poles. 




As conductors pass out of the influence of a N-poles and enter that of S-poles, the current in them is reversed.

This reversal of current takes place along Magnetic Neutral axis or brush axis.



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i.e. when the brush spans and hence short-circuit that perticular coil undergoing reversal of curremt through it.




This process by which current in the short-circuited coil is reversal while it crossres the M. N. A.  Is called Commutation.


The brief period during which coil remains short-circuted is know as Commutation period Tç.



  • If the current reversal i.e. the change from +I to zero and then to -I is completed by the end of short circuit or Commutation period. Then the Commutation is ideal. 

  • If current reversal is not complete by that time, then sparking is produced between the brushes the brush and the Commutator which results in progressive damage to both. 




Methods of improving Commutation
There are two practical ways of improving Commutation.


i.e. of making current reversal in the short-circuite coil as sparkless as possible. These methlds are know as

(1) resistance Commutation and

(2) e.m.f. Commutation( which is done with the help of either brush lead or interpoles, usually the later).





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Sunday, 21 January 2018

How Practical Generator Actually Appear!??

You Ever See?? That How A Practical Generator Was Actually Appear!!??




Different Parts Of Practical Generator 



Description





The simple loop generator has been considered in detail merely to bring ojt the basic principle underlying construction and working of an actual generator illustrated in figure. Which consists of the following essential parts:



  • 1)Magnetic frame or yoke
  • 2)pole-cores and pole-shoes
  • 3)pole coil or field coils
  • 4)armature core
  • 5)armature windings or conductors
  • 6)commutator
  • 7)brushes and bearings

Of these,  the yoke, the pole cores,  the armature core and air gaps between the poles and the armature core or the magnetic circuit whereas the rest form the epectrical circuit.

1) Yoke




It provides Mechanical Support for the poles and act as a proteting cover for the whole machine and its  carries the Magnetic Flux produced by the poles.

2)poles cores and pole shoes



They spread out the flux in the Air Gap and also being of large cross section reduce the reluctance of the Magnetic Path. They support the exciting coils

3)poles coil

When the current pass through the coil they Electro Magnetise the poles which produce the neccesery flux that is cut by revolving Armature Conductors. 

4)armature core

It house the Armature Conductor or ciol and cause them to rotate and hence cut the magnetic flux of the Field Magnets

5)armature winding




The Armature Winding are usually former wound. These are first wound in the form of flate rectangular coil and are then pulled into their proper shape in a coil puller.

6)commutator




The function of the commutator is to facilite collection of current from the armature conductor tors. And converts the Alternating Current in direct current.

7)brushes and bearings






The Brushes whose function is to collect the current from comuttator are usually made of Carbon Or Graphite and are in the shape of a rectangular block.


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Thursday, 18 January 2018

How To Convert Mechanical Energy To Electrical Energy!??

How To Convert Mechanical Energy To Electrical Energy!?? 



How We Can Convert The Mechanical Energy Into Electrical Energy By Using The Electrical Gemerator And Description About The Generator principle





An Electrical generator is a machine which coverts mechanical energy(for power)  into electrical energy (or power).

The Energy Conversion is based on the principle of the production of dynamically (or motionally)  induced emf.



As seen .


Whenever a conductor cuts Magnetic Flux,  dynamically induce e.m.f. is produce in it according to faraday's laws of Electromagnetic Induction.

This e.m.f. causes a current to flow if the conductor circuit is closed.

Hence two basic essential parts of an electrical generator are

  1.  a magnetic field and
  2. a conductor or conductors which can so move as to cut the flux.


Here How We Generate Electricity In The
Coal Based Thermal Power Station
Hydro Power Station
Nuclear Power Station

Simple loop DC Generator

Construction



In show in figer a single turn ractangular copper coil ABCD rotating about its own axis in a magnetic field provided by either Permanent Magnet is or electromagnet.


  • The two enda of the coil are joined to two slip rings.  'a'and 'b' Which are insulated from each other and from the Central Shaft.
  • Two collecting brushes (of carbon or copper)  press against the slip-rings. Their function is to collect the current induced in tge coil and to convey it to the External Load resistance R.


The rotating coil may be called 'Armature ' and the magnets as a 'Field Magnets'.




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Applications of Separately Excited DC Generators

This type of DC Generators are generally more expensive than self-excited DC Generators because of their requirement of separate excitation source. 

Because of that their applications are restricted. 

  • They are generally used where the use of self-excited generators are unsatisfactory.Because of their ability of giving wide range of voltage output, they are generally used for testing purpose in the laboratories.


Separately excited generators operate in a stable condition with any variation in field excitation. Because of this property they are used as supply source of DC Motors, whose speeds are to be controlled for various applications.

Example- Ward Leonard Systems of speed control.


Applications of Shunt Wound DC Generators


The application of shunt generators is very much restricted for its dropping voltage characteristic.


They are used to supply power to the apparatus situated very close to its position.

These type of DC Generators generally give constant terminal voltage for small distance operation with the help of field regulators from no load to full load.

  • They are used for general lighting.
  • They are used to charge battery because they can be made to give constant output voltage.

They are used for giving the excitation to the alternators.

They are also used for small power supply.


Applications of Series Wound DC Generators


These types of generators are restricted for the use of power supply because of their increasing terminal Voltage characteristic with the increase in load current from no load to full load.

We can clearly see this characteristic from the characteristic curve of series wound generator. 

  • They give constant current in the Dropping Portion of the characteristic curve. For this property they can be used as constant current source and employed for various applications.
  • They are used for supplying field excitation current in DC Locomotives for regenerative breaking.

This types of generators are used as boosters to compensate the voltage drop in the feeder in various types of distribution systems such as railway service.

In series arc lightening this type of generators are mainly used.


Applications of Compound Wound DC Generators


Among various types of DC generators, the compound wound DC generators are most widely used because of its compensating property. 


Depending upon number of series field turns, the Cumulatively Compounded generators may be over compounded, flat compounded and under compounded. 


We can get desired terminal voltage by compensating the drop due to armature reaction and ohmic drop in the in the line. Such generators have various applications.
  • Cumulative compound wound generators are generally used for lighting, power supply purpose and for heavy power services because of their constant voltage property. They are mainly made over compounded.
  • Cumulative compound wound generators are also used for driving a motor.


For small distance operation, such as power supply for hotels, offices, homes and lodges, the flat compounded generators are generally used.
The differential compound wound generators, because of their large demagnetization armature reaction, are used for arc welding where huge voltage drop and constant current is required.


At present time the applications of DC generators become very limited because of technical and economic reasons.


Now a days the electric power is mainly generated in the form of alternating current with the help of various power electronics devices.




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Monday, 15 January 2018

Major Applications In Various Field Of Laser Light!!

Major Applications In Various Field Of Laser Light!! 



All About LASER Light

  • LASER is an acronym for "light amplification by stimulated emission of radiation".
  • In Laser Light the intensity of light is amplified by a process called stimulated emission. 





Laser Light are optical phenomena which find major application in various field such as medicine, engineering,  fiber optics communication,  industries etc.  Laser are more powerfull radiation than ordinary light radiation.

Characteristics of laser

The following characteristics distinguishes a laser Light beam from an ordinary light.
1.Coherence
2. High intensity
3. High directionality
4. High monochromaticity

Laser Light is highly powerful and is capable of propagating over long distance and is not easily absorbed by water.




(1) Coherance


The wave trains which are identical in phase and direction are called coherent waves.
Since all the constituent photons of laser beam possess the same energy, momentum and propagate in same direction, the laser beam is said to be Highly Coherent.

(2)High intensity


Due to the coherant nature of laser, it has the ability to Focus  over a small area of 10^-6 (cm) ^2,i.e. extremely Highconcentration of its energy over a small area.

(3) High directionality


An ordinarry light source emits light in all possible direction. But, since laser travels as a parallel beam it can travel over a long distance without Spreading.

The angular spread of a laser beam is 1 mm/meter. This revels the Directionality of the laser beam.

The light from a normal monochromatic source spread over a range of Wavelenght of the order 400 nm.  But, the  spread is of the order of 1nm for laser. Hence, laser is highly monochromatic i.e. it can emit light of single wavelenght.


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Friday, 12 January 2018

Superposition Theorem Example | Aware About Most Useful theorem For Electrical Circuit That Supper Position Theorem!!!!

Superposition Theorem Example | Aware About Most Useful theorem For Electrical Circuit That Supper Position Theorem!!!! 




Superposition Theorem Example And How We Can Use The Supper Position Theorem In Electrical Circuit Is Given As Per Below Description 


The superposition theorem or superposition priciple is


" The Superposition Theorem states that the response in any element of a linear, bialateral network containing more than one independent sources can be obtained as the algebric sum of the responses obtained by each independent source acting separately at a time and with all other independent source set equal to zero."





While evaluting the responce from one independent source other source can not be removed bodily from the circuit.


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Insted, you suppress all other Independent Source by setting their values to zero. 

The suppressed source then behave like the following replacement.


  1. Ideal independent voltage source - short circuit
  2. Ideal independent current source - open circuit




Special care must be taken if the circuit also include the Controlled Sources.


In general a controlled source affect the individual contribution of each independent source,  Consequently Controlled Source are not suppressed during analysis by super position.
Example of Superposition Theorem calculation:

Superpostion Theorem Example



Question Related Supper Position Theorem:

1) superposition theorem applicable for ________ circuit????
Ans: linear Element Circuit

2) state the superposition theorem??
Ans:  the responce in any element of a linear, bialateral network containing more than one independent sources can be obtained as the algebric sum of the responses obtained by each independent source acting separately at a time and with all other independent source set equal to zero

3)In a superposition theorem Ideal independent voltage source will be???
Ans: - short circuit

4) In superposition theorem Ideal independent current source will be???? 
Ans: - open circuit

5) controlled source are suppressed or not during analysis by super position????
Ans : not suppressed




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Tuesday, 9 January 2018

Basic Knowledge Of Electrical Capacitor | About The Electrical Components Which Mostly Use In Electrical Application!!

Basic Knowledge Of  Electrical Capacitor |  About The Electrical Components Which Mostly Use In Electrical Application!! 





Get The Basic Knowledge Of Electrical Capacitor And Description For The Electrical Component - Electrical capacitor Which Are The Most Useful Device In Electrical Basic Circuits. 





Aa Capacitor is a passive two-terminal Electrical Component that stores Electrical Energy in an Electric Field.

The effect of aa capacitor is known as Capacitance

A While capacitance exists between any two Electrical Conductors of a circuit in sufficiently close proximity, 




A Capacitor is specifically designed to provide and enhance this effect for a variety of practical applications by consideration of size, shape, and positioning of closely spaced conductors, and the intervening Dielectric Material. 






We can understand the working of a capacitor by using the water tank analogy.

  • Imagine a water tank with fixed base area and height. The volume of the tank is the capacity of the tank to store water.
  • The height of the water in the water tank decides the potential energy of the water. For the same volume of water stored, a tank with lower base area and more height contains water with more potential energy than a tank with large base area and less height.
  • The rate of filling of the tank depends on the rate at which the water is poured into the tank.
  • If there is a leakage in the tank, some water keeps getting out of the tank, which is a wastage or loss.
Now, let's look at the capacitor:
  • The capacity to store charges is like the capacity of the tank to store water.
  • The voltage rating of the capacitor is analogous to the height of the water tank. A higher voltage rating ensures that the potential energy of the capacitor is more when fully charged [ Realation Between Electrical Charge And Electrical Current  ].
  • The rate of charging in a capacitor depends on the rate of flow of charges, which is current. It is analogous to the rate of flow of water into the tank.
  • All capacitors are lossy, which means that a charged capacitor subsequently loses its charge by slowly dissipating energy through it's loss component, which is a resistive component of a capacitor.






Capacitors are Energy storing elements, which store energy in the form of an electric field. 

When subjected to a voltage, a capacitor draws Current until the potential reaches the voltage rating of the capacitor. 

If a higher potential is applied, it may result in damage of the capacitor. 

The energy stored is directly proportional to the square of the voltage across the capacitor. 

Aa capacitor was  Historically [ History Of Electrical Engineering  ]  first known as an Electric Condenser.

The earliest capacitors were glass jars, metalised in and out.

they were made by Pieter van Musschenbroek of Leyden, Holland , who was exploiting a phenomenon observed the previous year by Ewald G. von Kleist, using simple medicine bottles.



Musschenbroek had been generating sparks and shocks with a static electricity machine, and used the jars as a medium term way of storing and transferring the effect.

This was 1746 and the jars became known as Leyden jars, presumably because no-one could spell Musschenbroek.

initially capacitance was measured in Jars, and the British navy was still doing that until after the second world war.

One RN Jar was about 1111pF. The size of the Jar (as a unit) had varied a bit, up to about 1910.

Glass jars are very good capacitors with a high breakdown voltage and low self-discharge

Type :- Passive

Invented :- Ewald Georg von Kleist


The physical form and construction of practical a capacitors vary widely and many capacitor types are in common use. 

Aa Most capacitors contain at least two Electrical Conductors often in the form of metallic plates or surfaces separated by a dielectric medium. 

Aa conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. The nonconducting dielectric acts to increase the capacitor's Charge capacity. 

i

Aa Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, and oxide layers. 

Capacitors are widely used as parts of Electrical Circuits in many common Electrical Devices. 

Unlike aa Resistor, an ideal capacitor does not dissipate energy.

Exampl Of Capacitors 

When two conductors experience aa potential difference, 

for example, when a capacitor is attached across a battery, 

an Electric Field develops across the dielectric, causing a net positive charge to collect on one plate and net negative charge to collect on the other plate.
  • A No current actually flows through the dielectric, however, there is a flow of charge through the source circuit. 

If the condition is maintained sufficiently long, the current through the source circuit ceases.

However, if aa time-varying voltage is applied across the leads of the capacitor, 

the source experiences an ongoing current due to the charging and discharging cycles of the capacitor.


Electrical Capacitor 

Capacitance is defined as a  the ratio of the electric charge on each conductor to the Potential Difference between them.

The unit of aa capacitance in the International System of Units (SI) is the farad (F), defined as one coulomb per volt (1 C/V).

A Capacitance values of typical capacitors for use in general electronics range from about 1 picofarad (pF) (10−12 F) to about 1 millifarad (mF) (10−3 F).


The capacitance of aa capacitor is proportional to the surface area of the plates (conductors) and inversely related to the gap between them

In practice, the dielectric between the plates passes aa small amount of leakage current.

It has an a electric field strength limit, known as the breakdown voltage.

The conductors and a leads introduce an undesired inductance and resistance.

Example Of Electrical Capacitors



Aa Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass.

Aa In analog filter networks, they smooth the output of power supplies. 

Aa In resonant circuits they tune radios to particular frequencies. 

Aa In electric power transmission systems, they stabilize voltage and power flow.

The property of energy storage in capacitors was exploited as dynamic memory in early digital computers aa.





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