KW & KVA ratings

Discussion in 'General Electronics Chat' started by aamirali, Mar 2, 2012.

  1. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    Can someone explians diff b/w KW & KVA & when dey r used for different devices
     
  2. mrmount

    Active Member

    Dec 5, 2007
    59
    7
    KW is the real power consumed by the device or circuit whereas KVA is the sum of real power and apparent power (reactive power) of a device or circuit.
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    KVA is KW divided by power factor.
     
  4. mlog

    Member

    Feb 11, 2012
    276
    36
    Apparent power is not the same as reactive power. Apparent power is the magnitude of the vector sum of real and reactive power.
     
  5. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    All students need to learn about:

    Watts (real power)

    VARs (volt-amps reactive, the reactive component of power)

    Volt-Amps (the vector magnitude of both real and reactive power.

    Another way to look at it: watts is the VA times the cosine of the angle to the real axis, and VARs is the magnitude of the VA vector times the cosine of the angle with the reactive (imaginary) axis.
     
  6. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    Why generators & inverters are rated in KVA while motors are in KW.
    What are the factors in any device by which it is rated in KVA instead of KW.
     
  7. crutschow

    Expert

    Mar 14, 2008
    12,988
    3,226
    Generators and inverters have to supply any reactive power to the load as well as real power, so they are rated in KVA. Motors use energy so it is important that the user know how much power it will draw from his mains supply. Ideally it would be good to know the motor's KVA rating so you would also know its power factor, but the manufacturers typically don't give that value.
     
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