TYPES AND CALCULATION OF CURRENT RATING OF DISTRIBUTION TRANSFORMER

RATING OF DISTRIBUTION TRANSFORMER WITH CURRENT RATING-
In distribution system there are basically 3 types of transformers(t/f)

1-low rating transformer
2- medium rating transformer
3-high rating transformer

low rating t/f contain -10 kva, 25 kva, 63 kva, 100 kva,

medium level t/f-250 kva 400 kva 630 kva

high rating t/f- 1 mva , 5 mva ,10 mva

all above distribution t/f are used on voltage-11 kv /440 v

and its current rating on lt side(440 v side) can be found  by 1.31* t/f rating= current rating

ex- current rating of 250 t/f- 1.31*250=325 amp

hence rating of t/f on l t side is 325 amp.

similarly rating on 11 kv side can be calculated by =current on l t side/25

ex-- for 250 kva transformer=325/25=13 amp.