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ee484
Joined: 04 Jan 2005
Posts: 161
Helped: 2
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 24 May 2006 14:01 difference between VA and W? |
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What are the difference??
VA = 500
W = 350
?
thanks
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elbadry
Joined: 06 May 2005
Posts: 363
Helped: 62
Location: Egypt
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24 May 2006 14:11 Re: difference between VA and W? |
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I am not sure but I think VA is the Early voltage. It is an indication of the output impedance
ro = VA/Ids
W is the width
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Kral
Joined: 28 Mar 2005
Posts: 1182
Helped: 187
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24 May 2006 14:19 Re: difference between VA and W? |
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ee484,
For simple sinusoidal waveforms, Power is the RMS voltage times the RMS current component that is in-phase with the voltage. P =VICos(Theta), where theta is the phase angle between voltage and current. As an extreme example, consider a purely capacitive load. In this instance, the current leads the voltage by 90 degrees. For 1/2 of the cycle, the capactor is drawing current from the source. For the other 1/2 of the cycle, the capacitor is supplying current to the source. The net power is zero (Cos[90 Degrees]) = 0.
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VA is simply the product of the RMS voltage and RMS current.
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For the example you give, the phase angle between the voltage and current is the arcCosine of 350/500.
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Non sinusoidal waveforms can be analyzed by doing a Fourier analysis of the voltage and current waveforms, analyzing each frequency component separately and adding the results.
Regards,
Kral
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xiaoqun
Joined: 24 May 2006
Posts: 8
Helped: 1
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25 May 2006 13:23 difference between VA and W? |
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| VA is usually used for transformer.
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Davood Amerion
Joined: 01 Mar 2005
Posts: 589
Helped: 90
Location: Persia
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25 May 2006 14:39 difference between VA and W? |
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VA (volt amper) is total power usage.
W (watt) is active power or resistive power.
W = V.A.Cos Φ
Φ is the phase difference between V and A
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25 May 2006 14:39 Ads |
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Miguel Gaspar
Joined: 06 Mar 2006
Posts: 391
Helped: 36
Location: Culiacán, Sinaloa, Mexico
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25 May 2006 20:06 Re: difference between VA and W? |
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VA (volt amper) is the active power, that is multiplication of Voltage (measured with volmeter) and current (also measured with volmeter), but there are the reactive power.
W (watt) is power is the add ,not algebraic but vectorial, of active and reactive power
Reactive power can't be measure by normal multimeter and this energy travels by the line and cannot be used by the Load.
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