lijojose
Branch Unspecified
13 Jan 2011

in most of machines rating is in KW. but in transformers it z in KVA ...
why?

deepaksr

Branch Unspecified
10 years ago
thats becoz u have to take care of power factor....

arunbasillal

Branch Unspecified
10 years ago
Hey. This question was asked to me in my 3rd sem Lab viva..

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

Branch Unspecified
10 years ago
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

Branch Unspecified
8 years ago
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

Branch Unspecified
8 years ago
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

Branch Unspecified
8 years ago
@ ARP
nice information.
You rock buddy!