generator is produced in current but supply the current from
motor is running in this differance between kva & kw

Generator is producer of Voltage and Current, we can 
connect load as such draining full load current or half 
load, even noload,but voltage remain moreover same.So it 
willl rated in terms of product of V*I, secondly it gives a 
electrical output for any Load(may Capacitor,Inductor & 
resistor),so it is consider as Procuct of Voltage & Current 
excluding powerfactor.
Whereas motor is machines coverts electrical Energy to 
Mechanical energy, so it is rated in KW

Transformer and genrator PF depends on the nature of 
connected load ( Motor ), But motor has its own fixed Power 
factor 

Therefore Transformer and genrator capacity shown in KVA ( 
Without PF ) and motor Capacity shows in Kw ( with power 
factor )