Electrical Engineering - Transformers - Discussion

Discussion :: Transformers - General Questions (Q.No.1)

1. 

What kVA rating is required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV?

[A]. 4 kVA
[B]. 0.25 kVA
[C]. 16 kVA
[D]. 8 kVA

Answer: Option C

Explanation:

No answer description available for this question.

Jitendra Patel said: (Nov 30, 2010)  
KVA = ( VOLTS * AMP )/1000 = ( 2000 * 8 ) /1000 = 16

Sarbojit said: (Jan 7, 2011)  
Why it is divided by 1000?

R.Ashok said: (Jan 22, 2011)  
Mr.sarbojit 1000 is dividing because we are taking the data as volts not in kv so after getting result we should convert into kv because there given only in kv.

Md Irshad Alam said: (Jan 28, 2011)  
The rating of transformer is represented in kilo volt so that it is divided by 1000, one kilo means 1000.

Madhusudhan. M said: (Jan 29, 2011)  
It's simple. A transformer transfors electrical power at one level of voltage & current to another another level of voltage & current without any change. With this basics we can say,

Apparent power=KVA= V1 * I1 = V2 * I2,

So, here KVA Rating = v2 * i2 = 2 kv * 8 A

= 16 KVA

Rohit said: (Feb 9, 2011)  
kva=v1/v2=i2/i1
is this right

Abhilash said: (Mar 10, 2011)  
Thank you sir.

Sudhandiran K said: (Mar 15, 2011)  
Actually we know the formula as

E2/E1=N2/N1=I1/I2
From this we have to consider
E2/E1= I1/I2
The secondary voltage is given ,so E2*I2=E1*I1
E1*I1=2Kv *8A
=16 KVA


Am I right

Ranjith said: (Apr 23, 2011)  
Transformer output power rating in KVA.

KVA=VOLTAGE X CURRENT =2X8=16.

Sweta said: (Apr 27, 2011)  
When transformer output rating in MVA then how can get the answers?

Faisal said: (May 2, 2011)  
If we wana take answer in MVA we will convert voltage from KVA to MVA by Dividing it by 1000

Sireesha said: (May 3, 2011)  
The transformer KVA rating is found out from the formula
Full load secondary current(I2) = KVA/secondary voltage(V2)
From this formula, KVA =I2*V2 = 8*2 = 16

Sanju said: (May 14, 2011)  
We know that t/f raiting is KVA
So,
kva=kilo volt*A(amp..)
2*8=16KVA

Milan said: (May 15, 2011)  
2000*8\1000=16

Jogi said: (May 23, 2011)  
KVA = V * A /1000 The raiting of transformer is Kilo Volt Ampeer so that it is divided by 1000.

Jogi said: (May 23, 2011)  
KVA = V * A/1000
The rating of transformer is Kilo Volt Ampere . So that it is dvided by 1000. 2KV= 2*1000=2000 SO . 2000*8=16000/1000=16KVA . This is the ans for above problem

Lingam Nayak said: (Jun 11, 2011)  
It's simple v2*i2=2kv*8
=16kv

Vishwanath said: (Jun 15, 2011)  
Sudhandiran K said really well nice explaination........

Narendra said: (Jul 11, 2011)  
p=vi
p=kva
v=2kv=2*1000v
i=8a
p=8*2*1000=16000va
p=16kva

Deepu.Pooji said: (Jul 23, 2011)  
Yeah..

8A*2KV=16 KVA

Azhagu said: (Aug 7, 2011)  
Output = Max I x Secondary voltage

= 8A *2000 V

= 16 KVA.

Chakri said: (Aug 14, 2011)  
kVA=(Secondary Voltage)*(Secondary Current)
=(2000*8)=16kVA

A.Harish said: (Aug 30, 2011)  
Load current means secondary current, already we know secondary voltage.

So output load is i*v=kva
i=8A and v=2KVA
So i*v=16kva.

Paresh said: (Sep 16, 2011)  
Why we rating in kva?

Rahul Prajapati said: (Sep 19, 2011)  
Because all losses ( core losses and copper losses ) are calculated in kva. That is why transformer is rated in kva.

K.Vijay Anand said: (Sep 21, 2011)  
KVA = ( VOLTS * AMP )/1000 = ( 2000 * 8 ) /1000 = 16

Gautam said: (Sep 29, 2011)  
KVA=(V*A)/1000=>(16000/8)=>16
KVA=16

Piyush said: (Oct 6, 2011)  
Because of we find kva that means we have to multiply with current so that.

Ans= 2kv*8 (given) =16kva.

Venkatesh said: (Oct 11, 2011)  
Suppose 2kv is given as 2v then what is the answer.

Navneet Kumar said: (Oct 29, 2011)  
kva
=volt*ampere/1000

=2000*8/1000

=16

Siva said: (Nov 21, 2011)  
KVA=V1*I1=V2*I2

KVA=(2000*8)/1000

it is divided by 1000 because it is representing in kva

KVA=16KVA

Archana said: (Dec 17, 2011)  
Actualyy rating of a transformer is in Kilo Volt ie KV
1KV = 1000 Volt
Therefore divided by 1000

Aditya Prasad Tripathy said: (Jan 4, 2012)  
We know that KVA=VOLATGE*CURRENT/1000
SO VOLTAGE =2 KV= 2000 VOLT
CURRENT=8 AMP

SO KVA = 2000 * 8 / 1000
=16000 /1000
16

SO KVA=16 SO SIMPLE.

Santhosh said: (Jan 6, 2012)  
Hello my dear friends we have to follow these steps to select transformer

we know that
p=VIcosQ for single phase and p=root3*v*i*cosQ for three phase
so power = 2000*8*0.95
= 15200= 15.2kw
Then

we know that power factor=KW/KVA

Consider 0.95 PF for transformer
0.80 PF for generator
so KVA=KW/PF=15200/0.95 = 16KVA

Santhosh said: (Jan 6, 2012)  
p=vicosQ for single phase p= root3*VICosQ for three phase
Consider 0.95 PF For transformer
0.80 PF for generator
p=2000*8*0.95
= 15200=15.2KW
so PF = KW/KVA we need KVA rating
KVA= KW/PF
= 15.2/0.95=16KVA.

Ravikant said: (Jan 13, 2012)  
Why the losses (c&i) are calculaed in kva of transformer why not in kw?

Sankar said: (Jan 23, 2012)  
kva=V*I
kva=2000*8
=16000
=16kva

Murali said: (Jan 31, 2012)  
The output rating of transformer in KVA=v*i
=2000*8
=16000
=16KVA

Murali said: (Jan 31, 2012)  
The output rating of transformer in KVA=v*i
=2000*8
=16000
=16KVA

Vimal said: (Feb 6, 2012)  
Mr madhusudhan.

By saying same voltage across the current & voltage in primary &secondary winding. Then, how could we step up &step down voltage of an transformer by using this concept?

Hareesh said: (Feb 14, 2012)  
p (k.w) = vi* p.f

Here secondary voltage = 2 kv

Total load = 8 amps
power factor =0.9

k.w =kva * p.f
= 2000 * 8 * 0.9/1000=14.4

kva = k.w /pf
=14.4/0.9=16 kva

Priya said: (Mar 8, 2012)  
Q=v*i*10^-3
Q=20000*8*10^-3
Q=16kva

P.H.Hussain said: (Mar 21, 2012)  
We know that,
Power P=voltage*current
P=2*8=16kw (or) 16kVA.

Virendra Mandloi said: (Apr 7, 2012)  
Why we note transformer's power in kva or mva? but why we do not in khva or mhva?

Bhushan Kumbhalkar said: (Apr 15, 2012)  
KVA=V1*i1=V2*i2.

Therefore here, V2=2KV, i2=8Amp.

Then, KVA=V2*i2.

KVA=2*8;

KVA=16.

Mohd Tajammul Akhter said: (Apr 17, 2012)  
The transformer rating in kva when 2kv is multiplied by 8a then it become 16kva.

L P Rai said: (May 6, 2012)  
We know
E2/E1=N2/N1=I1/I2
>E2/E1= I1/I2
>E1*I1=E2*I2
=2Kv *8A
=16 KVA

We should note (in this question) the rating of transformer meanse input kva rating the out put voltage and current i.e load current is already given.

Kedar Apkar said: (May 7, 2012)  
p=vicosQ for single phase p= root3*VICosQ for three phase
Consider 0.95 PF For transformer
0.80 PF for generator
p=2000*8*0.95
= 15200=15.2KW
So PF = KW/KVA we need KVA rating
KVA= KW/PF
= 15.2/0.95=16KVA.

Siri said: (May 23, 2012)  
Here how we can assume power-factor values?

Mohamed Mansoor said: (May 24, 2012)  
V2*I2=2*8=16.
Here load current=I2=8A

Jitendranath Panda said: (Jun 27, 2012)  
s/v - 2kv*8A = 16kva.

So 16kva or higher power transformer required.

Sindhuri said: (Jul 2, 2012)  
Power = Voltage*Current.

Power on load side = V2*I2.

Here P = 2kv*8A.

=16kvA.

Krishna said: (Jul 30, 2012)  
Transformer output power rating in KVA.

KVA=VOLTAGE X CURRENT =2X8=16.

Athi said: (Nov 2, 2012)  
We know that
p=VIcosQ for single phase and p=root3*v*i*cosQ for three phase

So power = 2000*8*0.95
= 15200= 15.2kw

Then

We know that power factor=KW/KVA .

Consider 0.95 PF for transformer.
0.80 PF for generator.
So KVA=KW/PF=15200/0.95 = 16KVA.

Vinoth said: (Dec 13, 2012)  
What is mean of isolation transformer?

Md Sultan Rashid said: (Jan 21, 2013)  
Isolation transformer is a transformer, which is used for transfer electrical power from a source of alternating current power to some equipment or device.

Vishal said: (Feb 21, 2013)  
What is mean of isolation transformer?

Ravi Sankar said: (Mar 13, 2013)  
What is the main advantage of parallel operation of two single phase transformers?

Raihan said: (May 1, 2013)  
The 3rd winding of a transformer called ?

Jexy said: (Jul 8, 2013)  
If a 1000kva 200hz transformer is operating at 50hz, its kVA rating is? please solve.

Ranjith Kumar said: (Aug 1, 2013)  
By using parallel operation load share equally in every T/R.

Ramesh Yadav said: (Aug 3, 2013)  
What will happen if t/f is made from magnet in place of iron?

Anshuman said: (Aug 19, 2013)  
Power = Voltage*Current.

Power on load side = V2*I2.

Here P = 2kv*8A.

=16kvA.

Mahantesh.Gm said: (Aug 25, 2013)  
Transformer output power rating in KVA.

KVA = V X I = 2X8 = 16.

Chiranjeevi said: (Sep 5, 2013)  
Transformer rating is in KVA(Apparent Power).

Apparent power = V*I = 2KV*8A = 16 KVA.

Pooja Gupta said: (Sep 19, 2013)  
WE KNOW THAT,

POWER ON LOAD SIDE,

SO,

P = V2*I2.

P = 8A*2KV = 16 KVA.

Mohan said: (Oct 2, 2013)  
When transformer output rating in MVA then how can get the answers?

Rahul Kumar said: (Nov 17, 2013)  
The given power is reactive power so how can we say it is a load,

Because reactive power did not require for a load but it work only with inductor and capacitor.

Charu said: (Dec 4, 2013)  
In transformer copper loss is depends on current ( I^2 R ) and core loss is depends on voltage, so only the rating of transformer is expressed in KVA.

So KVA = secondary current x secondary voltage.
KVA = 8 x 2.
KVA = 16 KVA.

Raja said: (Dec 29, 2013)  
Kva in primary = kva in secondary.

Maximum load = 8A = secondary current.

Secondary voltage = 2KV.

.'.KVA = Secondary current * Secondary voltage.
= 8*2*1000.
= 16Kva.

Subham Bahirlman said: (Jan 1, 2014)  
Why using this formula?

Arvind Chaudhari said: (Jan 2, 2014)  
KVA = (V*A)/1000 => (16000/8) => 16.

KVA = 16.

Pummy said: (Jan 18, 2014)  
The rating of transformer is given in KVA because the what type of load will connect with the x"mer is not defined.

Akash said: (Apr 10, 2014)  
KVA = Kilovolt * Ampere.
KVA = 2KV * 8A.
KVA = 16KVA.

Sudipt Jena said: (May 21, 2014)  
Transformer is always rated in kva or mva instead of kilowatt or megawatt because of the absence of power factor unlike the motors. And this kva or mva can be derived by multiplying the system voltage with the current. Here the system voltage is 2000 volts and current is 8 amp.

Vijay said: (May 24, 2014)  
Well question itself gives us the secondary voltage as well as load current i.e.,secondary current and we know that kva=current*voltage (either primary or secondary).

2kva*8A = 16kva.

Chandragupt Morya said: (Jun 4, 2014)  
Hello friend,

You know that,
Output = i*v.

So,

= 8*2.

= 16KVA.

Manukumari.M said: (Aug 22, 2014)  
KVA/KV = I.
KVA/2 = 8.
KVA = 16.

Sankurathri Brahmaraju said: (Aug 23, 2014)  
Hai friends, transformer ratings is always measured in KVA.

kva:v*i - (1000*2*8) - 16000 - 16kva.

Madhav said: (Sep 19, 2014)  
It is simple.

p = v*i.
= 8*2.
= 16.

Raghaba Pradhan said: (Sep 23, 2014)  
Put the formula and get the answer KVA = VI.

Rabbani said: (Sep 27, 2014)  
Simple KVA = voltage*current.

So as per the question we know voltage = 2kva and current = 8A.
So 2*8 = 16kva.

Rabindra Das said: (Nov 22, 2014)  
Transformer always rating in KVA that means voltage *current.

So 8*2 = 16 KVA.

Pravin said: (Nov 30, 2014)  
But friend transformer reading in kva.
That means p = vi cos phi power factor.

Ubaid said: (Dec 19, 2014)  
Because of two type losses in transformer (Core losses and iron losses. Core losses occur from voltage and iron losses occurred from currant) is T/F rating in KVA.

Jaydeep said: (Jan 26, 2015)  
How to we know the transformer is single phase or three phase?

Bijith said: (Feb 17, 2015)  
There are lot of factors to find a transformer single or three phase,

1. Ratings.
2. No of windings.
3. Size (may be).

Sumit said: (Feb 24, 2015)  
Kva = V *I = 2KV* 8A = 16 KVA.

Engr.Zameer Baloch said: (Mar 18, 2015)  
V*A = 8*2 = 16 kva.

Jaydeep said: (Mar 30, 2015)  
How we can calculate if kva is given and we have to find out maximum current rating 2kva transformer find max current rating?

Kiran said: (May 6, 2015)  
Guys, some come across true power and apparent power and some tell us about copper lose and core loss but I am convinced with @Santosh answer after that @Sudipt told there will be no pf then its tricky again want to know pf should be considered or not in calculation.

Kiran said: (May 6, 2015)  
Pf = True power/Apparent power.

Pf = Kw/Kva.

Kva = Kw/Pf.

P = v*i*cos Q = True power.

Pf for transformer is 0.95.

So P = 2000*8*0.95.

P = 15200 = kw.

Kva = 15200/0.95 = 16000 VA.

Kva = 16 KVA.

Akshay said: (Sep 4, 2015)  
Can we change the rating of transformer by using some method?

Akshay said: (Sep 4, 2015)  
What is more loss in transformer?

Omardayah said: (Sep 6, 2015)  
We know that transformer has voltage and ampere.

So we have to multiply volt and amp 2V and 8A is 16's term of KVA is a unit of transformer.

Saranraj R said: (Oct 13, 2015)  
Generally we know that ratings of transformer is denoted as kVA then from the given:

KV = 2.

Amps (A) = 8.

Then, (kVA) = 2*8 = 16 kVA.

Sakthimadhan said: (Dec 21, 2015)  
V*A = VA.
2000*8 = 1600 VA.

KVA = 1600/1000.
KVA = 16.

Hakim said: (Jan 11, 2016)  
Apparent Power (VA) = Root-square 3*V*I. That is for 3 phase transformers only.

Apparent Power (VA) = V*I. That is for single phase transformers only.

In the equation they did not mentions the type of the transformer either single or three phase.

Garima said: (Jan 19, 2016)  
In short circuit test iron loss is negligible why?

Swarup said: (Feb 6, 2016)  
kv*A = kvA.
8*2 = 16.

Belal Momin said: (Feb 29, 2016)  
Because in short circuit test current flow through low resistance path & maximum amount of current flow this sc path that's why iron loss is negligible as compare with copper loss.

Rakesh Kumar said: (Apr 8, 2016)  
kVA rating = EI. Here 8 amp and secondary voltage are given then multiply both then we
get 16.

Sanjay Verma said: (Apr 10, 2016)  
How to find PF?

Sasenthiran said: (Jul 2, 2016)  
Kv * A = kvA,

8 * 2 = 16.

Sasi said: (Jul 13, 2016)  
Friends, this is my interview question.

Please explain transformer with ohms law.

Sree said: (Aug 6, 2016)  
kva rating = v × i = 2000 × 8 = 16000.

Jayadeva said: (Aug 15, 2016)  
The output power of transformer is depending pf, so it is not to be rated for kw.

ex, if v = 10V.
A = 2A.
pf = 0.8.

P = v * i * pf .
p = 10 * 2 * 0.8 ,
p = 16w.

And

p = v * i.
p = 10 * 2,
p = 20.

Gyanprakash said: (Sep 12, 2016)  
Thank you for all the solution and explanation.

Sachin said: (Oct 25, 2016)  
@All.

Thanks for the explanation.

Venkatesh Badgujar said: (Nov 14, 2016)  
It is 16 volt * current.

Ujjawal Patle said: (Nov 17, 2016)  
v * A = 2000 * 8\1000 = 16kva.

Meet Vekaria said: (Nov 24, 2016)  
For a 300 MW steam turbine, Generator output is designed 353 MVA and transformer is designed for 370 MVA. Why are generator and transformer rating different?

Kavyashree G said: (Mar 4, 2017)  
All electrical devices that supply power are usually rated in kVA. This includes transformers, UPS's.

Praveen J said: (Jul 6, 2017)  
V2*i2 = kVa.
So,
2* 8= 16 kVa.
Ans:- 16 kVa.

Ramniwas said: (Aug 24, 2017)  
Thanks to all your explanation.

Ranjit Rai said: (Sep 30, 2017)  
Thanks all for explaining it.

Abhishek said: (Feb 14, 2018)  
Why transformer's rating is in Kva and not in Kw?

Roopesh said: (Mar 22, 2018)  
Have any formula for change to kW to ka?

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