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Phase Shift In AC Sine Wave

spongebillybob

Jul 13, 2010
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Jul 13, 2010
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Hello Folk,

Just wondering what effect the phase shift (whether leading or laggin) in an AC sine wave actully has on a load. Is this more prevalent in audio/video applications? It just seems to me that the RMS values would still be the same and anything that the shift could effect would have to be sensitive enough to detect instantaneous voltages/currents. I am probably overthinking this, but any assistance would be appreciated.

Thank you.
 
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Harald Kapp

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Nov 17, 2011
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I suppose you mean phase shift between voltage and current, do you?
Typically this phase shift is introduced by the load itself or some circuitrx in front of the load (where this circuitry itself is a load as seen from the power source).
A phase shift will reduce the available power at the load, because at some time during the sine wave's periode the voltage and current will have opposite signs which means that the instantaneous power becomes negative. This happens when the load returns some of the power thatit has drawn from the power supply back to the supply. This is energy that was stored e.g in the magnetic field of a coil or the electrostatic field of a capacitor.

It is not correct to multiply the rms values of current and voltage. Look up this explanation or try these tools.
 
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