Thursday, 29 March 2018

You Know How Many Types Of Connection Of Three Phase Transformers???

You Know How Many Types Of Connection Of Three Phase Transformers??? 




Here You Can Get Knowledge About The Different Types Of The Connections Of Three Phase Transformers And Also That Description!!! 





There are Different Methods for connecting 3-phase transformers to transform 3-phase voltages to Higher Or Lower Value.




The HV and LV windings of a 3-phase transformers can be connected either in star or delta.


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The choice of a Particular Connection depends upon the conditions under which the transformer is to be operated.


The Most Common and widely used transformer connections and their features are as follows:


(1) Star/Star 




->This is the most economical connection for small, high voltage transformers.


->As the phase voltage Vphase=<(V)line/(root )3>   it needs lesser turns per phase and insulation requi is mmimum


-> Possibility to provide neutral connection. The star point can be used in case of 3phase four wire system.

  • -> The third harmonic voltages are absent from the line voltage. However, the third harmonic phase voltages may be high for shell type of three phase units
  • -> This connection is more suitable for core type transformers.



(2)Delta/ Delta




-> This connection is more suitable for large, low voltage transformers.


-> It increases the number of turns per phase and reduces the necessary cross-sectional area of conductora, thus insulation problem is not present.


-> It gives satisfactory performance even if there is large unbalanced in load.

  • ->The third harmonic voltages are absent due to elosed delta.
  • ->The absence of star or neutral point is the disadvantage of this connection.


(3) Delta/Star or Star/Delta



->This connection is most commonly used for power supply transformers


->The neutral point allows both type of load 1-phase and 3-phase to be met.


->The delta connected winding carrie third harmonie current due to which potential of neutral point is stabilized.
  • ->The HV side is normally connected in delta so that the 3-phase loads and 1-o loads can be supplied by LV side using three phase, four wire system.


(4)zig zag connection (Interconnection between phases) 


->This connection reduces the third harmonic voltages

->It allows unbalanced loading.

-> This connection is mainly employed for LV winding.


-> For a given total voltage per phase, the Zig Zag side requires 15% more turns as compared to normal phase connection.

  • ->Zig Zag connection is used where delta connections are mechanically weak (due to largo number of turns and small cross- section of conductor in case of delta) in high voltage transformers. 
  • It is also used for rectifiers.



Question part about The different types of connections of three phase transformer :


(1)Which is the most economical connection for small, high voltage transformers. ???
Ans:star/star


(2) Which connection have Possibility to provide neutral connection. ??
Ans:star/star


(3) Which connection is more suitable for large, low voltage transformers.??
Ans:Delta/Delta


(4)which connection is satisfactory performance even if there is large unbalanced in load. ??
Ans:Delta/Delta


(5)what is disadvantage of Delta/Delta connection of transformer?? 
Ans:The absence of star or neutral point


(6)The third harmonic voltages are absent from the line voltage in which connection??? 
Ans:star/star and delta/delta


(7)Which connection is most commonly used for power supply transformers ???
Ans:star/delta or delta/star


(8)what is advantage of star/delta or delta/star connection?? 
Ans:The neutral point allows


(9)Which connection reduces the third harmonic voltages ??
Ans:Zig-Zag connection


(10) For a given total voltage per phase, the Zig Zag side requires how many turns as compared to normal phase connection. ??
Ans:15% more



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Saturday, 24 March 2018

You Know When We Can Do The Parallel Operation Of Transformer!??

You Know When We Can Do The Parallel Operation Of Transformer!?? 



What is The Requirements For Operation Of Parallel Operations Of Transformers!!  And What is Use Of Parallel Transformers!! 





The Transformers are said to be connected in parallel when the primaries of two or more transformers are connected to a common source or supply and the secondaries are connected to supply a Common Load.




All the transformers to be connected in parallel should be of the same construction either core type or shell.


Necessity of Parallel Operation of transformers

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The Parallel Operation Of Transformers is necessary due to the following



(i) to supply the load in excess of the rating of an e Existing Transformer, an additional transformer can be connected in parallel


(ii) when one transformer in taken out of service for maintenance or repair, The Other Transformer maintains the continuity of supply to the consumers


(iii) if any one transformer fails to operate, there is no Interruption of The Power Supply


(iv) to increase the relinbility of The Power System

Parallel Operation Of Three Phase Transformers


The Conditions for proper and satisfactory parallel operation of two or more 3-phase transformers are as follow:

Essential conditions:




  1. (i) Same polarity
  2.  (ii) same voltage ratio
  3. (iii) same phase sequence
  4. (iv) Zero relative phase displacement


In addition to the above Essential Conditions, the desirable conditions to be satisfied for better load sharing and operating power factor are

(i) Equal per unit impedances and
(ii) Equal ratios of resistance to reactance(R/X)


Question part to Related This Article  :


(1)when The transformers are said to be connected in parallel????
Ans: when the primaries of two or more trannformers are connected to a common source or supply and the secondaries are connected to supply a common load.


(2)Necessity of parallel operation of transformers???
Ans:(i) to supply the load in excess of the rating of an e existing transformer, an additional transformer can be connected in parallel

(ii) when one transformer in taken out of service for maintenance or repair, the other transformer maintains the continuity of supply to the consumers

(iii) if any one transformer fails to operate, there is no interruption of the power supply

(iv) to increase the relinbility of the power syetem


(3)give essential condition of connection of transformer in parallel??? 
Ans:(i) Same polarity
 (ii) same voltage ratio
(iii) same phase sequence
(iv) Zero relative phase displacement


(4), give the desirabal conditions to be satisfied for better load sharing and operating power factor in parallel connection of transformer????
Ans:
(i) Equal per unit impedances and

(ii) Equal ratios of resistance to reactance(R/X)



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Wednesday, 21 March 2018

What Is The Tap Changing In The Electrical Transformers ?

What Is The Tap Changing In The Electrical Transformers ? 



What Is The Use Of Tap Changing In Transformer And How Its A Useful For The Output Of The Transformation!! 




The Tap Changing may be done when the transformers are disconnected from the circuit or when Operating On Load.






Tap Changer is fitted with the transformer for adjusting the Secondary voltage.


The modern practice is to install the tap-changer with the Transformer Tank.

There are two types of Tap-changers:


  • (i) OFF-circuit Tap Changer
  • (ii) ON-load Tap Changer (OLTC)




OFF-Circuit Tap Changer 

(A) 

Abov Figer(A) show the arrangement of off-load Tap Changers.

Normally (+)or(-)2.5  and (+)or(-)5% tappinge are provided on The Transformer Winding for regulating the voltage.

Occasional Adjustments in second voltage can be made by off circuit Tap changer .

The tap can be changed only after opening the circuit breaker on supply aide i e. The transformer is disconnected from the circuit.



ON-load Tap changer (OLTC)

The daily or Short Time Voltage Adjustments is made by ON- load tap changer (OLTC).

The tappings of ON-load tap changer can be changed without interruption of load current or Power Supply.

Figer(B) shows in below the Basic Diagram of ON-load tap changer(OLTC).

(B) 

The Tap Changer is operated by motor drive unit by local or remote control and a handle also fitted for manual operation in case of an emergency.

The pair of resistors are provided to limit the short cireuit current-during the operation of Tap Changer

The Tapping are provided on the high voltage(h. v.) winding as shown in Figer (C) because of the following reasons:

(C) 


  • (i) The number of turns in High Voltage winding (h.v.) is large and therefore a fine voltage regulation can be obtained.
  • (ii) The Current on the h.v. side is small.
  • (iii) The Lv. winding is placed on the inside nearer to the core while hv winding is placed on the outside.


Therefore, from Practical Considerations it is proferred to provide on hv winding.





Question part Of This Article Which helps You For Better Understanding :

(1)when we can done tap changing in transformer???
Ans:The tap-changing may be done when the transformers are disconnected from the circuit or when operating on load.


(2)how manny type will be there for tap changing in transformer???
Ans:There are two types of Tap-changers:
 (i) OFF-circuit Tap Changer
(ii) ON-load Tap Changer (OLTC)


(3)which type of tap changing is made by ON- load tap changer (OLTC). ??
Ans:The daily or short time voltage adjustments .


(4)give the reason The tapping are provided on the high voltage(h. v.) winding?????
Ans:reason is give as below:
(i) The number of turns in High Voltage winding (h.v.) is large and therefore a fine voltage regulation can be obtained.
(ii) The current on the h.v. side is small.
(iii) The Lv. winding is placed on the inside nearer to the core while hv winding is placed on the outside.


(5)practical considerations tap changer is proferred to provide on which winding.??

Ans: high voltage



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Thursday, 15 March 2018

What Is The Application Of Potential Transformers ???

What Is The Application Of Potential Transformers ???




How We Can Use The Potential Transformer To Find The Value Of The Voltages!!? 



Potential Transformers are used for the uannformation of voltage from higher values to a lower values that are suitable for Measurement And Protection.




Potential Transformers are used for measurement and protection. The VA rating of PT is very small compared with Power Transformers.



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  1. The Secondary Voltage rating of PT is usually 110 V.
  2. Potential Transformers consist of two separate windings on a magnetic core. One winding consist of few turns of thick wire and is called the Secondary Winding
  3. The other winding consists of a relatively large number of turns of thin wire and is called Primary Winding.



Figer shows the Connection Diagram for a potential transformer .


The voltage to be measured in applied to the primary winding of PT and the secondary is connected to the meter .


The primary of PT is connected directly to Power Circuit between phase and ground and the Secondary Terminals are connected to the meter or relay.

Ratings of PTs



  • (i)  Rated secondary voltage : 110V or 220V
  • (ii) Rated output 10, 25, 50, 100, 200 and 500VA

For Lower Voltages up to 3.3kv dry type PTs are used and for high voltages oil immersed PTs are used.





Question part about Potential Transformer :

(1) what is Potential transformer?????
Ans: potential transformer  are used for the uannformation of voltage from higher values to a lower values.


(2)Potential transformers are used for ?????
Ans:meaaurement and protection.


(3)potential transformer winding consist of few turns of thick wire and is called which winding?? 
Ans:The secondary winding


(4)which is the primary winding of the potential transformers??? 
Ans:which have  relatively large number of turns of thin wire and is called primary winding.


(5)For lower voltages up to 3.3kv which type potential transformer are used??? 
Ans: dry type PTs are used


(6)for high voltages (more than 3.3kv) which potential transformer is used???? 

Ans:oil immersed PTs are used


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Monday, 12 March 2018

What is The Application Of Current Transformer ??

Current Transformer - Which A Device That Use To Measure A Value Of Current In The Electric Line!!! 



How We Can Use Current Transformer In to Measure The Current Value And What Is The Function Of The Current Transformer!! 




A CT is a device for the transformation of current from a Higher  Values to a lower values that are suitable for measurement of the relay operation.




Besides Reducing The Current level, the CT also isolates the measuring circuit or relay circuit from the primary high power circuit.


The VA rating of CTs is very small as compared with Power and Distribution Transformers.


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The primary winding of the CT consists of one or few turns of thick wire and is connected in series with the line or load and carries the actual Power System Currents.




The Secondary Winding consists of large number of turns of thin wire and is connected to the measuring circuit or the relay

According to the construction, the CTs can be Classified into two ways


  • (i) Bar primary CTs or single turn CT wound type
  • (ii) Wound type CT




In bar primary type CT, he primary is a Straight Conductor passing through the centre of a hollow core and the secondary has a ring hollow core type iron core on which the wound uniformly over the entire periphery.





shows a bar or single turn  CT. This type of construction of CT has a Negligible Leakage flux and hence low reactance.




The wound type CTs have Magnetic Core. Figer shows wound type CT.

The two windings are wound on a magnetic iron core.

The primary winding consists of a few turns of thick wire, they can not be distributed uniformly over the iron core.

Therefore wound type CTs have high Leakage Flux and hence posseses high reactance.




Question part Related To The Current Transformer!! 

(1)What is the current transformer???? 
Ans:A CT is a device for the transformation of current from a higher  values to a lower values that are suitable for measurement of the relay operation.


(2)The VA rating of CTs is ?????
Ans:very small


(3)primary winding of current transformer have how many ternes???
Ans:The primary winding of the CT consists of one or few turns of thick wire


(4)give type of current transformer according to construction!!?? 
Ans:According to the construction, the CTs can be classified into two ways

(i) Bar primary CTs or single turn CT wound type
(ii) Wound type CT


(5)describe bar type CT?? 
Ans:In bar primary type CT, he primary is a straight conductor passing through the centre of a hollow core and the secondary has a ring hollow core type iron core on which the wound uniformly over the entire periphery.


(6)short not on wound type CT?? 
Ans:The wound type CTs have magnetic core. Figer shows wound type CT. The two windings are wound on a magnetic iron core. The primary winding consists of a few turns of thick wire, they can not be distributed uniformly over the iron core. Therefore wound type CTs have high leakage flux and hence posseses high reactance .


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Wednesday, 7 March 2018

What Is A Advantage Of Scott Connection Of 3- Phase Transformer!!

What Is A Advantage Of Scott Connection Of 3- Phase Transformer!! 




How We Can Apply Scott Connection In The Three Phase Transformers!!?? 



The conversion of 3-phase AC supply to two-phase AC or vice-versa can be achieved by this connection and  is needed for the following applications:




  • 1) to supply power to two-phase electric furnaces
  •  2)to inter 3 ase and 2-phase systems
  • 3)to supply power to a 3-phase apparatus from a two-phase source and vice-versa



Scott Connection requires a 3-phase power input and provide two equal single phase outputs.


These outputs are 900
degree out of phase and must not be connected in parallel or in series as it creates a Vector Current imbalance on the primary side.






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Figer (a)  shows the schematic diagram of scott connection of transformers.


(A) 

Two Single Phase Transformers of identical rating with suitable provided on both, are required for the scott connection.


The tappin transformers used for this conversion must have the following pings on their primary windings


Transformer T1: 50% tapping and is called main transformer

Transformer T2: 86.6% tapping and is called teaser transformer


The Main Transformer T1 is centre-tapped at D and is connected across the lines B and C of the 3-phase side.



It has primary BC and secondary and secondary a1a2.


The Teaser Transformer is connected between the line terminals A and the centre tapping D. It has primary AD and secondary b1b2.

(b) 

The Phasor Diagram of voltages across the primaries and secondaries shown in figer (b).




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Saturday, 3 March 2018

Essential Consist In Three Phase Transformers!??

Essential Consist In Three Phase Transformers!??



Different Parts Of Electrical Transformer 




(1) Magnetic Circuit


                  

Which consists of cores and yokes and provides path of flux





 (2) Electric circuit



An Electric Circuit consist of LV and HV windings. The windings ara electrically separated but magnetically linked through a path of low reluctance.


(3) Dielectric circuit



Which consists of Insulation in different forms and used at different places in transformer. The Insulation is provided between LV and HV windings and core to LV winding.

(4) Tank and accessories



This includes cooling system, oil conservator, breather, bushings, Buchholz relay and other protective devices.


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Question part of this Article  :

(1)Which part consists of cores and yokes and provides path of flux in three phase transformer???

Ans:magnetic circuit


 (2) Electric circuit which type of part consists????
Ans:An electric circuit consist a of LV and HV windings. The windings ara electrically separated but magnetically linked through a path of low reluctance.

(3)What is the work of dielectric circuit part in three phase transformer??? 
Ans:. The insulation is provided between LV and HV windings and core to LV winding.



(4)which parts consisting in  Tank and accessories In the three phase transformer???
Ans:This includes cooling system, oil conservator, breather, bushings, Buchholz relay and other protective devices.

(5) what is a work of magnetic circuit in three phase transformer???
Ans:provides path of flux

Thursday, 1 March 2018

You Know What Is Advantage Of 3 Phase Transformer!!!

Advantage Of 3-Phase Transformer - You Know What Is The Advantages Of Three Phase Transformers??? 



widely Used Applications is Electrical Transformer, Here The Description All About Advantage  Of Electrical Transformer??



A 3-phase AC system is used to generate and transmit Large Amount Of Power.

Single phase transformer construction 
Three phase transformers contruction

Three Phase transformers are used to step up and step down AC voltages in various stages of a Power System The construction of a single 3 phase transformer is preferred over a bank of three 1phase - transformer due to the following advantages


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  • (1) It occupies less floor space for equal ratings
  • (2) It is lighter in weight.
  • (3) Smaller size for the same rating. 1phase


Single phase transformer winding 
Three phase transformers construction 



  • (4) A 3- phase transformer is cheaper than a bank of three transformers.
  • (5) It requires few bushings.
  • (6) Less transformer oil is used.
  • (7) It requires 1/3 as much iron for the magnetic circuit as compared to a bank of three 1-phase transformers.
  • (8) More efficient.


(A) 


  • A 3-Phase Transformer actually consists of 6 windings, three primary and three secondary.

(B) 
These Windings are usually connected either in delta or star. A 3 phase core type transformer consists of a three- legged iron core. Each leg has a respective LV and HV winding as shown in figer (a) and (b).



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