Monday, 30 April 2018

List The Method For Testing DC Machine!??

List The Method For Testing DC Machine!??




There Are Three Method For Testing of DC Machines And Check The Efficiency Of The Electrical DC Machines  And Get All Rates Of All Properties Of The DC Machines ! 

Three Method in Testing of DC machine


The Methods for Testing Of DC Machines can be broadly classified into three methods:




  • 1) Direct method
  • 2) Indirect method
  • 3)Regenerativo method



(1)Direct method





In this Method Of Testing, the DC machine is loaded directly by means of Mechanical Brake coupled to the shaft of the machine.


  • The efficiency of the machine is cnlculated directly by measuring the power input and output. 

  • The entire power output is wasted at the mechanical brake. 


Due to non-availability of large capacity loads for testing large machines in the laboratories, this method is used only for testing small DC machines.


Brake Test is the example of direct test.




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(2) Indirect method




In this method of testing, the losses [ Here Totle Losses In DC Machines Fully Explanation  ]  are determined without actual loading of the machine.

If the Total Losses in the machine are known, the efficiency can be calculated.

The Swinburne's test is the simplest indirect testing method for finding out the efficiency of dc machine.


(3)Regenerative method 





This method requires two identical dc machines.

One of the machines  is operated as a Motor And Drives the other machine as a generator Both the machines are mechanically coupled and electrically connected.

The electrical output of the generator is feedback into the supply. the power drawn from the supply is small only to overcome the losses of the two machines.


Hence the Large Machines can be tested at rated load without consuming much power from the supply The Hopkinson's test is a regenerative method of testing for dc machines.




Question part Related To This Article :


1)how manny and which  test for dc machine?? 
Ans:1) Direct method
2) Indirect method
3)Regenerativo method



2)what is direct test?? 
Ans: In this method of testing, the de machine is loaded directly by means of mechanical brake coupled to the shaft of the machine.

The efficiency of the machine is cnlculated directly by measuring the power input and output.

The entire power output is wasted at the mechanical brake. Due to non-availability of large capacity loads for testing large machines in the laboratories, this method is used only for testing small de machines.



3)break test is example of which test?? 
Ans:direct test


4)Swinburn's test is simplest which type of test?? 
Ans: Indirect


5)what is indirect test?? 
Ans:In this method of testing, the losses are determined without actual loading of the machine.

If the total losses in the machine are known, the efficiency can be calculated.


6)give one example of regenerative test of dc machine?? 
Ans: hopkinson's test



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Wednesday, 25 April 2018

What Is All Day Efficiency Of Transformer !??

What Is All Day Efficiency Of Transformer !??



All About The All Day Efficiency Electrical Transformer , Its A Useful Or Not And How To Calculate The All Day Efficiency Of Electrical Transformers!!!! 




(A) ordinary or commercial efficiency


The Commercial Efficiency Of a Transformer is defined as the ratio of power output to power input in (watts or kilowatts)




Commercial efficiency =  output in watts or kW / Input in watts or kW






(b) All-day efficiency


Transformers used to stepdown the Distribution Voltage to a standard service voltage or from transmission voltage to distribution voltage are called distribution transformers.

For Getting Knowledge Of Basic Principles Of Electrical Transformer Is Here :: Basic Principles Of Electrical Transformer 



They are connected for the whole intermittentle.


Day to the line but loaded whether they They are kept in operation all the 24 hours a day are carrying any load or not.

Thus the iron losses occur for the whole day but Copper Losses occur only when the transformer is delivering the load current.





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Hence if the transformer is not used to supply the Load Current for the whole day, all day efficiency will be less than ordinary or commercial efficiency.




The All Day Efficiency is defined as the ratio of energy output in kwh to the input in kWh during the whole day.


Efficiency (all day)  = Output in kWh /Input in kWh for 24 hours


In order to determine the all-day efficiency, the load cycle (or the period for which the transformer is loaded) in 24 hours should known.



Question part Of Related This Article Which May Helping You For Better Understanding :


1) what is ordinary or commercial efficiency of transformer?? 
Ans:The commercial efficiency of a transformer is defined as the ratio of power output to power input in (watts or kilowatts)


2)what is distribution transformer??
Ans:Transformers used to stepdown the distribution voltage to a standard service voltage or from transmission voltage to distribution voltage are called distribution transformers.


3)define the all day efficiency of transformer?? 
Ans:The all-day efficiency is defined as the ratio of energy output in kwh to the input in kWh during the whole day.


4)give equation of all day efficiency of transformer?? 
Ans:Efficiency (all day)  = Output in kWh /Input in kWh for 24 hours


5)give commercial efficiency of transformer?? 
Ans:Commercial efficiency =  output in watts or kW / Input in watts or kW

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Friday, 20 April 2018

How Electricity Produce In Coal Based Thermal Power Plant??

How Electricity Produce In Coal Based Thermal Power Plant?? 




Working And Process Of Coal Based Thermal Power Plant And How Will Be Produced The Electricity Produced In This Power Station,. 





Energy Generating [ By Electrical Generator  ] station which converts heat energy of coal combustion into electrical energy is known as a steam or thermal power station.





basically Energy Generation By Coal Base Thermal Power Plant.

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A Steam Power Station basically works on the Rankine cycle. Steam is produced in the boiler utilizing the heat of coal combustion.
Here Read The Different Types Of Electrical Energy Conversion : Electrical Energy Conversion 

The steam is then expanded in the prime mover (i.e Steam Turbine) and is condensed in a condenser to be fed into the boiler again.


The steam turbine drives The Alternator which converts mechanical energy of the turbine into electrical energy. This type of power station is suitable where coal and water are available in abundance and a large amount of electric power is to be generated



The Generated Energy efficiency of a conventional Thermal Power Station, considered salable energy produced as a percent of the heating value of the fuel consumed, is typically 33% to 48%. As with all heat engines, their efficiency is limited, and governed by the laws of thermodynamics.


Schematic Arrangement of Thermal Power Station


Although steam power station simply involves the conversion of heat of coal combustion into Electrical Energy, yet it embraces many arrangements for proper working and efficiency.

The schematic arrangement of a Modern Steam Power Station is shown in Figer.




The whole arrangement can be divided into the following stages for the sake of simplicity:


  • 1) Coal and ash handling arrangement
  • 2)Steam generating plant
  • 3)steam turbine
  • 4)Alternator
  • 5)Feed water
  • 6) Cooling arrangement




1. Coal and ash handling plant 

The coal is transported to the power station by road or rail and is stored in the coal storage plant.

Storage of coal is primarily a matter of protection against coal strikes, failure of transportation system and general coal shortages.

From the Coal Storage Plant, coal is delivered to the coal handling plant where it is pulverised (i.e., crushed into small pieces) in order to increase its surface exposure, thus promoting rapid combustion without using large quantity of excess air.

The pulverised coal is fed to the boiler by belt conveyors. The coal is burnt in the boiler and the ash produced after the complete combustion of coal is removed to the ash handling plant and then delivered to the ash storage plant for disposal.


The removal of the ash from the boiler furnace is necessary for proper burning coal.


 2, Steam Generating Plant




The Steam Generating plant consists of a boiler for the production of steam and other auxiliary equipment for the utilisation of flue gases

Boiler:

The heat of combustion of coal in the boiler is utilised to convert water into steam at High Temperarure And Pressure.

The flue gases from the boiler make their journey through superheater, economiser, air pre-heater and are finally exhausted to atmosphere through the chimney.





Superheater

The steam produced in the boiler is wet and is passed through a superheater where it is dried and superheated (i.e., steam temperarure increased above that of boiling point of water) by the flue gases on their way to chimney. Superheating provides two principal benefits. Firstly, the overall efficiency is increased.

Secondly, too much condensation in the last stages of turbine (which would cause blade corrosion is avoided.

The superbeared steam from the superheater is fed to steam turbine through the main valve.


Economiser

An economiser is essentially a Feed Water Heater and derives heat from the flue gases for this purpose.

The feed water is fed to the economiser before supplying to the boiler The economiser extracts a part of heat offlue gases to increase the feed water temperarure.




 Air preheater

An air preheater increases the temperature of the air supplied for coal burning by deriving heat from flue gases.

Air is drawn from the atmosphere by a forced draught fan and is passed through air preheater before supplying to the boiler fumace.

The air preheater extracts hear from flue gases and increases the temperarure of air used for coal combustion.

The principal benefits of preheating the air are: increased thermal efficiency and increased steam capacity per square metre of boiler surface



3. Steam turbine: 

The dry and superheated steam from the superhearer is fed to the steam turbine through main valve.

The heat energy of steam when passing over the blades of turbine is converted into mechanical energy.

After giving heat energy to the turbine, the steam is exhausted to the condenser which condenses the exhausted steam by means of cold water circulation.




4. Alternator

The steam turbine is coupled to an alternator.

The alternator converts mechanical energy of turbine into electrical energy.


The electrical output from the alternator is delivered to the bus bars through transformer, circuit breakers and isolators


5. Feed water:

 The condensate from the condenser is used as feed water to the boiler. Some water may be lost in the cycle which is suitably made up from external source.

The feed water on its way to the boiler is heated by water heaters and economiser. This helps in raising the overall efficiency of the plant.



6) Cooling arrangement

 In order to improve the efficiency of the plant, the steam exhausted from the turbine is condensed by means of a condenser.

Water is drawn from a natural source of supply such as a river, canal or lake and is circulated through the condenser.


  • The circulating water takes up the heat of the exhausted steam and itself becomes hot. This hot water coming out from the condenser is discharged at a suitable location down the river. 

  • In case the availability of water from the source of supply is not assured throughout the year, cooling towers are used. 


During the scarcity of water in the river, hot water from the condenser is passed on to the cooling towers where it is cooled.

The cold water from the cooling tower is reused in the condenser.

Question Part Related To This Article Which Helps You For More Understanding :


1)What is a Thermal Power Plant??
Ans:A generating station which converts heat energy of coal combustion into electrical energy is known as a steam or thermal power station


2)Thermal Power Plant is suitable for ____????
Ans:This type of power station is suitable where coal and water are available in abundance and a large amount of electric power is to be generated.


3)What is function of super heater in thermal power plant??
Ans: The steam produced in the boiler is wet and is passed through a superheater where it is dried and superheated (i.e., steam remperarure increased above that of boiling point of water) by the flue gases on their way to chimney.

Superheating provides two principal benefits. Firstly, the overall efficiency is increased. Secondly, too much condensation in the last stages of turbine (which would cause blade corrosion is avoided. The superbeared steam from the superhearer is fed to steam turbine through the main valve.


4) What is work of economiser in thermal power plant??
Ans: An economiser is essentially a feed water heater and derives heat from the flue gases for this purpose.

The feed water is fed to the economiser before supplying to the boiler The economiser extracts a part of heat offlue gases to increase the feed water temperarure.


5)Which type And Why cooling arrangement are required in thermal power plant??
Ans:  In order to improve the efficiency of the plant, the steam exhausted from the turbine is condensed by means of a condenser.

Water is drawn from a natural source of supply such as a river, canal or lake and is circulated through the condenser.

The circulating water takes up the heat of the exhausted steam and itself becomes hot.

This hot water coming out from the condenser is discharged at a suitable location down the river.

In case the availability of water from the source of supply is not assured throughout the year, cooling towers are used.

During the scarcity of water in the river, hot water from the condenser is passed on to the cooling towers where it is cooled. The cold water from the cooling tower is reused in the condenser .




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Sunday, 15 April 2018

What Is Full Form Of LED?? And About LED

What Is Full Form Of LED?? And About LED



Here This Article Present Full Form Of LED And All About LED Light And Application Of LED Light!!! 




In a Forward-Biased Diode, free electrons cross the junction and fall into holes.

When they recombine, these free Electrons Radiate Energy as they fall from a higher energy level to a lower one.

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In a Rectifier Diode, the energy is dissipated as heat, but in an LED, the energy is radiated as light




By using elements like gallium, arsenic and phosphorous, a manufacturer can produce LEDs that radiate red, green, yellow, orange, and Infrared Radiation (invisible).


LEDs that produce visible radiation are used in instrument displays, calculators, digital watches, etc.




The infrared (IR) LED finds applications in Burglar-Alarm systems and other areas requiring invisible radiation. Generally, the infrared emitting LEDs are connected with phosphor so that, by the excitation of phosphor, visible light can be produced.



The advantages of using LEDs in electronic displays are.

1). LEDs are very small and can be considered as point sources of light.

They can, therefore, be stacked in a high density matnx to serve as a numeric and Alphanumeric Display


2) The light output from an LED is a function of Current flowing through it. An LED can. therefore, be controlled smoothly by varying the current.

This is particularly useful for operating LED displays under different ambient lighting conditions.


3). LEDs are Highly Efficient emitters of EM radiation. LEDs light output of different colours, i e. red, yellow, amber, and green are commonly available.


4) LEDs are very fast devices, having a turn-on/off time of less than 1 ms.



5) The low Supply Voltage and current requirements of leds make them compatible with TTL ics.


6. LEDs are manufactured with the same type of technology as that used for Transistors and ICs and, therefore, they are economical and have a high degree of reliability




7) LEDs are rugged and can, therefore, withstand shocks and vibrations.They can be operated over a wide range of temperature say, 0-70degree C.



The disadvantage of LEDs compared to LCDs is their High Power requirement.

Also, LEDs are not suited for large area displays, primarily because of their high cost.

Question Related to This Article  :

What is the possible range of current limiting resistor essential for lightening the LED in certain applications after pressing the push-button?
Ans:  220- 330 Ω


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Thursday, 12 April 2018

What Is Statement Of Ohm's Law And Where Its Use??

What Is Statement Of Ohm's Law And Where Its Use?? 




There Is The All About The ohm's Law Like What Is Ohm's Law , How We Can Apply In The Electrical Circuit!! 





Statement of Ohm's law:

The Ohm's Law states that the ratio of potential difference(V) between any two point and The Current flowing between them is constant if tempreture is constant.

This ratio is turmed as resistance R.
V/I = constant = R Ohms.




Ohm's Law deals with the relationship between voltage and current in an ideal conductor.



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This relationship states that: The Potential Difference (voltage) across an ideal conductor is proportional to the current through it.

The constant of proportionality is called the "Resistance", R.


Example, that we have a circuit with the potential of 1 volt, a current of 1 amp, and resistance of 1 ohm. ... The amount of water in the tank is defined as 1 volt and the “narrowness” (resistance to flow) of the hose is defined as 1 ohm.




The Ohm's law is not applicable to any non-linear device as diode, transistor, zener diodes etc.

Its applicable only to the linear device.




Coulomb's law 

Coulomb's law states that: The magnitude of the electrostatic force of attraction between two point Charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them. The force is along the straight line joining them.



Question part related to ohm's law :


(1)stat the ohm's law??? 
Ans:The Ohm's law states that the ratio of potential difference(V) between any two point and the current flowing between them is constant if tempreture is constant. This ratio is turmed as resistance R.


(2)give equation of ohm's law?? 
Ans:V/I = constant = R Ohms.


(3)give one example of ohm's law?? 
Ans: we have a circuit with the potential of 1 volt, a current of 1 amp, and resistance of 1 ohm. ... The amount of water in the tank is defined as 1 volt and the “narrowness” (resistance to flow) of the hose is defined as 1 ohm.


(4)state the coulomb law?? 
Ans:The magnitude of the electrostatic force of attraction between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them. The force is along the straight line joining them.


(5)give ohm's law limitation?? 
Ans:The Ohm's law is not applicable to any non-linear device as diode, transistor, zener diodes etc .


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Friday, 6 April 2018

Which Is The Indirect Methods For Testing Of Transformer???

You Know Which Indirect Test Use For The Testing Of Transformer?? 



There Is The Indirect Method For Testing Of The Electrical Transformer!!  And How We Can Proceed The Indirect Methods On The Electrical Transformers!!! 




The Performance of a Transformer at any load and Power Factor can be determined without actually loading the transformer by conducting the following tests:




  1. (i) Open Circuit (O C.) test and
  2. (ii) Short Circuit (S. C.) test

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These tests are convenient and economical because the power required to test a transformer is very small.


(i) Open circuit or No load test 



The Aim Of Conducting this test is to determine the following.
[ Here This Losses Accure In Electrical Machines ]
  • (a) Iron losses
  • (b) No-load current and
  • (c) No-load equivalent circuit parameters (Ro and Xo)


The Experimental Circuit diagram for conducing open circuit (o.c.) test on a transformer is shown in figer(A)

In this test, The Primary Winding (preferebly low voltage winding) is supplied primary and frequency rating of the with normal voltage as per the transformer and the secondary (High Voltage Winding) is left open


  • To measure no-load current and no load power input, an Ammeter And Wattmeter of low range are connected in the primary circuit. The Supply Voltage can be measured with the help of voltmeter



  • As the iron losses depend upon supply Voltage And Frequency, this test is performed at normal supply voltage and frequency


Since the Normal Voltage is applied to the primary winding, the flux set up in the core of transformer will have a normal value so that normal iron losses will occur


The no-load primary current being very small (2 to 5% of full current), the copper losses in the primary winding will be negligible and there will be no Copper Losses in the secondary winding, sin open circuited us the reading of the wattmeter indicates practically the iron losses under No-load condition .


It is preferred to keep h.v. winding open and normal voltage applied during this test because it is difficult to obtain high voltages in the laboratories.


Also in certain cases, no load current of h.v. winding maybe extremely small, which might not be measured accurately.


(ii) Short Circuit Test

The purpose of this test is to determine the following:


  1. (a) Full-load copper losses
  2. (b) Equivalent impedance (Z1, or Z2) referred to metering side.
  3. (c) Voltage regulation



The Experimental Circuit diagram for conducting short circuit test on a Single Phase Transformer is shown in figer(B).


In this test, usually low voltage winding is kept short-circuited and a reduced voltage of Normal Frequency (hardly 5 to 8% of rated voltage) is applied to the high voltage winding.

The applied reduced voltage is gradually increased till full-load currents are flowing both in primary and secondary windings


As The Applied Voltage is very low, the iron losses will be very small and can be neglected.


Hence the total losses occurring under this test are mainly the copper losses of both the windings, which are indicated the wattmeter.

Question part of this Article  :



(1)when The performance of a transformer at any load and power factor can be determined without actually loading the transformer by which test???
Ans:(i) Open Circuit (O C.) test and
 (ii) Short Circuit (S. C.) test


(2)O.C. and S. C. testes which type of test and why??? 
Ans:These tests are convenient and economical because the power required to test a transformer is very small.


(3)by open circuit test which type property we can find?? 
Ans:The aim of conducting this test is to determine the following.
(a) Iron losses
 (b) No-load current and
(c) No-load equivalent circuit parameters (Ro and Xo)



(4)In open circuit test which winding will be open?? 
Ans:H.V.


(5)using short circuit test which property we can find?? 
Ans: (a) Full-load copper losses
(b) Equivalent impedance (Z1, or Z2) referred to metering side.
(c) Voltage regulation


(6)In short circuit test which winding will be shorted??? 
Ans:L.V.


(7)When in the short circuit test the applied voltage is very low that timr the iron losses will be ???
Ans:very small


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Tuesday, 3 April 2018

Anyone Know What is Back To Back Test Or Sumpner Test! !?

Anyone Know What is Back To Back Test Or Sumpner Test! !? 




What is Used Of Back To Back Test And We Can Apply The Back To Back Test In Transformer!! 




This Test On Transformer is performed for finding efficiency, regulation and heating (Temperature Rise) under loaded conditions.



The O.C. and S.C. tests on Transformers are conducted to determine its performance i.e. efficiency and regulation without actually loading the transformer but cannot give heating information under Load Condition.


In Sumpner's Test, actual loading conditions are simulated and hence it is more Accurate Method of determining the efficiency and regulation than O.C. and S.C. tests

(A) 

Two Transformers Of Identical Rating are needed to perform this test Figer(A) shows the experimental circuit diagram for performing Sumpner's test on two identical rating single phase transformers .




The Primary Windings of two transformers are connected in parallel and are energized at rated voltage and frequency with the Secondary Windings open.


  • As secondaries of both transformers are open, The Wattmeter W1 reads the iron losses of both transformers. The secondaries of both transformers are connected in phase-opposition.

  • Their polarities can be checked by means of voltmeter connected across the switch If The Voltmeter reads zero, it means that the secondaries are in phase opposition and the switch (S) can be closed.


In case the voltmeter reads the secondary voltages, the secondaries are in same phase.

order to bring them in phase opposition, interchange Secondary Terminal of one of the transformer



A Reduced Voltage (hardly 5 to 10%) is applied across the secondary windings so that full load rated currents flow in both the secondaries and by transformer action, the primary windings also carry rated full- load currents.


  • As the Applied Voltage is very low, the iron w be very small and can be neglected.


A single phase variac can be used in the secondary circuit to obtain a reduced voltage.


As the full-load current is flowing in Secondary Circuit, the wattmeter reads full load copper losses of both the transformers.



Questions Related Back To Back Test :


(1)sumpner test is use for????
Ans: This test on transformer is performed for finding efficiency, regulation and heating (temperature rise) under loaded conditions.


(2)what is advantage of sumpner test?? 
Ans: In sumpner's test, actual loading conditions are simulated and hence it is more accurate method of determining the efficiency and regulation than O.C. and S.C. tests.


(3)which and how manny transformers are use in sempner test?? 
Ans:Two transformers of identical rating are needed to perform this test .



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Sunday, 1 April 2018

What Is Thumb Rule For Magnetic Field??

What Is Thumb Rule For Magnetic Field?? 




You Know What is Thumb Rule For Magnetic Field And How We Can Use This Rule In The Practical Application!? ?




As shown in Figer(A)



if the Straight Conductor is held in the right hand such that the thumb indicates The Direction of Current then the other fingers curled around the conductor point the direction of Magnetic Field.



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The Corkscrew Rule

Consider a right handed screw or wood screw shown in Figer(B).



When This Screw is to be inserted in a wooden plank, it is to be rotated in the Clockwise Direction.

If the direction of advancement of the screw indicates the direction of current, then the circular Rotational Motion of the screw indicates the direction of the magnetic field.



Question part of this article :

(1)what is right hand thumb rule???
Ans:if the straight conductor is held in the right hand such that the thumb indicates the direction of current then the other fingers curled around the conductor point the direction of magnetic field.



(2)what is the corkscrew rule???
Ans:When this screw is to be inserted in a wooden plank, it is to be rotated in the clockwise direction.

If the direction of advancement of the screw indicates the direction of current, then the circular rotational motion of the screw indicates the direction of the magnetic field.


(3)in the right hand thumb rule the finger is give direction of????
Ans:direction of field



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