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Why DC value isn't 0 when the power supply is AC?

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daddeeee

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when i measure ac voltage using multimeter i get a 10v and simultaneously if i measure dc voltage it gives me 3-4 v(why not dc value is 0 when the power supply is ac)?
 

ac and dc

well as per my knowledge the ac is always super imposed on some dc component...thatz why..
or may be the value u saw was the rms value.......may b....not sure...
 

Re: ac and dc

Your ac waveform is distorted and not a pure sine wave. This is common on the grid supply. There are lots of harmonics in the signal.
 

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    daddeeee

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Re: ac and dc

It means your ac voltage isn't pure AC and has an average dc offset voltage of 3-4V. It could be due to the harmonics sourced from the supply lines or there could be some interference with your measurement or the circuit itself.
 

Re: ac and dc

The ac-dc rectifier you are using is not well designed. You will get a better response if you give the details of the rectifier (OR how you are getting the dc you are measuring). The ripple factor of that rectifier is quite high (i.e. a dc component is super-imposed by an ac component).
Have a look at this book: Power Converter Circuits by William Shepherd & Li Zhang
link:
 

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