Answer Posted / pillay

We buy/fix a motor to do a specific job.Job done is measured in watts.So a machine say a pump will use up to 3 KW to run as designed than we fix a motor of 3KW or slightly bigger to run it.Now the motor is 3KW or bigger say 30 KW and the voltage is AC or DC operated is up to you.

generators are rated in KVA because we dont know at what pf will it be operated. Say you have fitted a pf correction board to maintain at 0.95pf, you dont have a guarantee it wont breakdown or take some time to adjust. What is important the generator voltage is constant and the generator dont trip or burn.So if the pf can change anytime the current also can change anytime this may make your generator to trip on overcurrent,overvoltage(leading pf)or even destroy your genset.By rating your generator by KVA with a constant designed voltage you can know the maximum current the genset can give irrespective of pf.It is a safer and sure way of protecting your generator.you can even load yor genset at 0.2 pf so long you dont exceed the rated amps or KVA.

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