pradyumna chandra panda


{ City } berhampur
< Country > india
* Profession * asst.foreman in electrical.
User No # 95772
Total Questions Posted # 18
Total Answers Posted # 41

Total Answers Posted for My Questions # 43
Total Views for My Questions # 123418

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Answers / { pradyumna chandra panda }

Question { KCP, 216389 }

why transformer ratings in kva?


Answer

Why the Transformers are rated in KVA?
Ans . Motor is a consuming device it consume the power
(wt) so it is rated in KW. But the
Transformer is a static device which transfers
the power (Apparent power) from the
Generating point to the user. Apparent power is
the product of voltage and current
I.e. Increase voltage with decrease current and
decrease voltage with increase current. Power factor of the
load does not share with main losses (Iron and copper) it
affects the Active Power which share of apparent power.

Active power is the real power which the transformer
gives. Transformer should not be rated on the base of
Active power (KW) which is variable because the power factor
of the load is not knows before which to be connected across
the transformer.


Active power is equal to apparent power at resistivity load
where power factor is unit at cos Q is equal to zero degree.
Active power is decrease power where cos Q (not fi) is
increase
Therefore in simple we can say due to unknown power factor
of load, transformer and alternator are rated in KVA.
Hint – we know cos FI is the value of cos Q i.e. Apparent
power/ active power.


Transformer input is Apparent power in KVA----- In
Transformer Apparent Power is reduced by Iron loss (k) &
Copper loss --- On Transformer output Active power in KW



PRADYUMNA CHANDRA PANDA

BRG STEEL

Is This Answer Correct ?    1 Yes 0 No

Question { KCP, 216389 }

why transformer ratings in kva?


Answer

Power given to the transformer is Apparent power (K)
it is the supply power of the power house and the power
given by the transformer to the Load is the true power or
Active power which is actual used by the load and rest is
the reactive power i.e. square of apparent power including
iron loss & copper loss in KVA = square of true power in KW
+ square of reactive power in KVAR. A sound transformer
efficiency is 98% (input power- Iron loss (k) & copper loss
= output power).
For full resistive load (at unity pf ) a 100 KVA transformer
gives 100 KW (approx.) true power, and for inductive power
at .8 pf the same will able to give 80 KW (approx.) true
power, but the types of load (its pf) is not know before
which to be connected across the transformer, this is only
why the transformers are rated in KVA and it is meaningless
to discuss about the iron loss and copper loss because the
Inventor and UPS are also rated in KVA.


In other hand or in simply we can say due to unknowing power
factor the transformer, generator etc are rated in KVA. In
heavy size transformer copper loss is more and it vary with
load and Clemet i.e. transformer oil condition but it is not
main reason to rating the transformer in KVA.


Pradyumna Chandra Panda
Berhampur Mob 9861357949

Is This Answer Correct ?    1 Yes 0 No


Question { Jindal, 98723 }

What is Difference Between Induction Motor & Servo Motor


Answer

Speed ie. the No of rotation from switch ON to after switch OFF is unknown in induction motor but there is specific ( run at reference) in servo motor .

Is This Answer Correct ?    0 Yes 0 No

Question { TATA, 15563 }

In 3 phase induction motor 1hp current rating is 1.5 amps
constant ? is correct or not ?


Answer

It is not justificable that current rating of 3ph motor is culculate to 1.5 amp per hp. Reactive power is more in higher size hp motor ie. slight less current per hp. And reactive power is less in lower size hp motor ie. more current per hp. Normaly 3ph 1hp motor take 1.8 amp per phase (phase current) Simiarily current rating of 3ph 5hp is 7.5 amp, 10hp is slight less then 15 amp and 100 hp motor is approximately 140 amp.

Is This Answer Correct ?    5 Yes 2 No

Question { 9388 }

Difference between KW & kVA


Answer

in other hand we can say that kw is the real power which is used by a load(*) and kva is the supply power required to meet that load(*).

Is This Answer Correct ?    2 Yes 0 No

Question { 25984 }

IF 5000amp current on LT 440V. then how much it will draw
amp on HT 11KV side


Answer

5000/25=200amp (Receprocal ratio of voltage i.e 11000/440=25)

Is This Answer Correct ?    1 Yes 0 No

Question { 6739 }

Why DC Currents are not used in transformer?


Answer

In transformer there is verry small resistance in primary winding it stand with ac supply because itself an inductive load ( leg the current). but there is no possible of legging current in dc supplly if we give it in transformer the primary winding will be burn out due to small resistance of primary winding and no emf will induced in secondary winding due to failure of mutual induction.where flux linkage is not possible.

Is This Answer Correct ?    2 Yes 1 No

Question { 6380 }

What size cable is used for HT cable to the transformer of
630kVA, and the supply voltage is 11kV


Answer

k prakaschandra is correct. * 35 sqmm 3core aluminium conductor is sufficient because 630KVA transformer full load current is 31.5 amp and 35 sqmm al conductor can take 70 amp current.

Is This Answer Correct ?    4 Yes 2 No

Question { 25651 }

how many voltage or current enough to kill a person?


Answer

A person feel shock by 24 volt / 35 mili amp but it depend on iron contain in blood, and total resistance offer by body. the person kill by shock it depend on plasma contain in the blood , time period and heart mental conditon of the victime. A person may kild by 230 volt ac in 10 minut and escape from 11 kv for few second , there is less dc voltage required to kill a person in less period than ac voltage.

Is This Answer Correct ?    1 Yes 4 No

Question { Sail, 19505 }

what is the basic difference between synchronous
motor,synchronous generator and induction motor


Answer

Induction motor is easily self started and it's speed is variable which is less than synchronous speed and motor leg the current behind the voltage ie poor power factor. In simple Synchronous motors are not self started (they are self started by Drive) it's speed is equal to synchronous speed and the motor maintain approximately unity power factor ie not legging.

Is This Answer Correct ?    5 Yes 0 No

Question { Siemens, 8973 }

why we use 3 phase in our country?..why no 4,5 or 2??


Answer

In 3 phase supply phases are120 degree electrical aparts each and for a technician it is easy to use such connect the machine with sequence or obtain uniform rotating magnetic field in motor, so India follow this.

Is This Answer Correct ?    17 Yes 5 No

Question { Bhel, 8639 }

what happen when dc supply is given to the transformer


Answer

Primary winding of transformer has very low resistance it act a indictive load on ac supply so it is easily stand . but legging current is not possible in dc supply, the primary will burn when it connected with dc supply due to small resistance. And mitual induction is not possible in dc supply so no emf will induced in secondary winding. N.B Armature resistance of dc motor is very low but it can stand due to back emf.

Is This Answer Correct ?    3 Yes 0 No

Question { 3225 }

what is power transformer?


Answer

Delta-Delta HT transformers are called power transformer.

Is This Answer Correct ?    6 Yes 1 No

Question { 4950 }

1. what is exciting winding, rotor winding, startor
winding. and how it works? in ac generator


Answer

Field winding of ac generator is act as exciting winding and it wound in rotor to collect more power from stator (armature)or in stetor where rotor act armature. Intially there is some residual magnet in field winding and gradualy increase with increasing rpm by collect emf from armature stepdowned by 24 volt dc or more. some time it is seperatly excited by a battary or by a dc generator.

Is This Answer Correct ?    6 Yes 0 No

Question { 7624 }

why the transformer neutral earthing is to be done by copper
flat only,if we use GI flat what is the disadvantage.


Answer

Earth electrod should have low resistance and copper flate meet it. IF we use GI flate then potentional between earth &neutral will be increase on unbalance load, but it is allowed only 20 volt . we can decreare the earh resistance by increance the electrode in parallel.

Is This Answer Correct ?    8 Yes 0 No

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