Answer / pradyumna chandra panda

By help of power trangle pf= value of cos thita (cos fi)=
b/h=active power/apparent power. Active power (kw)is the
real or true power which the transformer give for a
aparticular load (useed power)and Apparent power(kva)is the
supply power for that particular load. That a 100 kva
transformer can supply/give 100 kw resistive load and
incase inductive circuit a 100 kva rtransformer give 80 kw
inductive loadat at.8 pf,and 75 kw inductive load at.75 pf
etc but the pf of the load is not known before that which
types load (resistive,inductive or capacitive)to be
connected across the suplly, this is only why the
transformers and Alternaters are rated in kva and it is
meaningless discuss about iron loss & copper loss because
the UPS and inventers are also rated in kva.

Answer / praphulla bansal

KVA is mentioned to take care of PF issues of the load. At the same time, rating of transformer is given a limiting PF. This means a 100 KVA transformer and limit of 0.8 PF will limit load to 80 KW irrespective of load PF as unity.

Answer / md. abdullah al mamun

I think Copper loss of a transformer is related to current
and core losses are related to voltage so that VA should be
the rating of a transformer. But in a large transformer it
is rated it KVA. Also KVA rating Indicate the Maximum
Current Rating of a transformer with a rated voltage.

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