since the losses in transformers are mostly due to copperlosses and corelosses which in turn depends on current and voltage ( ie., copper loses is nothing but i^2R losses depends on current and core losses v*i depends on the voltage) hence the transformer ratings are taken in KVA but not in KW.
1.cgs- centimeter, gram and second sysytem mks- metre, kilogram and seconds systems which means that all quantities are represented in d respective dimensional units acc 2 d sysytem applied
2. i did nt understand ur 2nd q, be a bit more specific
3. thr is no difference betwn earthing and grounding, jus difference terms used in d u.s and england repectively
Transformer rating is always in KVA rather than in KW. it is due to the fact tha the core loss inside the conductor (which are mainly hysteresis loss and eddy current loss) depends upon the voltage and the iron loss depends upon the current core loss=v^2/R and the iron loss = i^2R. Tansformer is a static device so there is no rotational losses, so the vi input is aproxly equal to vi output hence one can write: vicosk1=vicosk2 hence cosk1= cosk2. The transformer is the device which have highest efficiency among electric machinery; because it does not have mechanical and ratational losses.
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