installed power vs transformer rating

Size the transformer for the intended load (including any estimated new loads due to expansion, etc), peak motor and compressor load, environmental de-rating (such as high ambient temperature, you could be in Dubai for all I know). Get a transformer that is of a higher rating than what you estimate you need. Protection of the transformer is primarily performed by the circuit breaker or fuse protection on the main transformer feeder and the branch feeders powering the different loads in the building.

You really should be getting someone qualified to do this for you, is this for a cost estimating or tender proposal?

Thank you for prompt response.This is for verification purpose as the order had been placed for 100 kva.

dear,

Following may justify ?

Application : Residential , i.e. un balanced load.

Installed load : 190 KW

Power factor for L&F with ACs : 0.55 average.

Load factor : normally 0.45 , night times, with AC , 0.65

Demand on transformer : Normal - 155 kva , Peak - 224 kva

We suggest after derating with ambient., 250 KVA transformer minimum

with 200% Neutral for internal winding of transformer.

( unbalanced currents that can flow in neutral shall be 1.732 * Ir max.