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lijojose
lijojose • Jul 6, 2008

Question about transformer rating

in most of machines rating is in KW. but in transformers it z in KVA ...
why?
deepaksr
deepaksr • Jul 6, 2008
thats becoz u have to take care of power factor....
arunbasillal
arunbasillal • Jul 6, 2008
Hey. This question was asked to me in my 3rd sem Lab viva..
Here goes the answer.

KW shows the power consumed by a machine. Transformer is not a power consuming device, its a power transfer device. So the actual power consumed depends on the load applied to the secondary. As Deepak SR said the power consumed depends on the power factor of the secondary load.

To calculate the KW rating, just multiply the KVA rating by the powerfactor if the seconday. So a 1000 KVA transformer when connected to a 0.7 pf secondary loaed used 1000*0.7= 700 KW power.. Got it..?
manivannan.mv
manivannan.mv • Jul 9, 2008
deepaksr
thats becoz u have to take care of power factor....
if you don't mind please the complete explanation about mva rating in transformers😒
Arp
Arp • Jan 13, 2011
transformer is rated in kva because what we want to know from the rating of a power transfer device is only about the losses practically speaking
core loss proportional to voltage and cu loss to current
and with r(in pu) and kva we can directly estimate cu loss and with v we can think of core loss directly
other reasons are major thing in electrical transformer is insulation and it is prop to voltage and wdg are design on the basis of current rating so these two ratings are need to be specified.. by specifying kva and v
we havenot choose kva and i as insulation is major
and not i and v as to calculate full load cu loss it need calculation and majorly as it does not represent the capacity of a transformer(with how much power it is able to deal with)
nsiva007
nsiva007 • Jan 13, 2011
Remember KVA is a measure of apparent power..! Not all loads are Purely resistive for which the unit is KW , loads can be inductive loads as in motors,in which case there is a power factor.. and hence you have to go for a KVA rating in transformer..!
freak16
freak16 • Jan 13, 2011
@ ARP
nice information.
You rock buddy!

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