# KW & KVA ratings

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

1. ### aamirali Thread Starter Member

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

2. ### mrmount Active Member

Dec 5, 2007
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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
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1,194
KVA is KW divided by power factor.

4. ### mlog Member

Feb 11, 2012
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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
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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
2
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
22,814
6,756
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.