Hi guys,
When I was reading through several papers regarding to THD to learn more about it I noticed something strange. To be honest it seems there is AT lEAST 2 definitions for THD which are not the same!
One defination is at the begining of page #297 of this:
https://books.google.com/books?id=y...resnum=10&ved=0CF4Q6AEwCQ#v=onepage&q&f=false
The other defination is here:
https://docs.google.com/viewer?a=v&...GA_ho-&sig=AHIEtbQyYpfnDa85EGyc4f3eKdQUpGYOfg
If we suppose that the Voltage of both the fundamental frequncy and the secondharmonic for instance happens to be 4v, then for the formula of the first link the THD would be:
THD= √16/√32 =0.707 =70.7%
But regarding to the formula of the second link it would be:
THD= √16/4 =1=100%
I myself think that the formula of the second link is correct as it gives 100% of THD for when both fundamental and the second harmonic of a waveform which contains just both of them with the same amplitude would be 100% not 70.7%.
So any idea plz?
The other question is that why we must use "RMS" values of a Voltage when want to calculte the THD of a signal? You know that V1p/V2p of a signal is equal to its V1rms/V2rms. so?
Thanks
When I was reading through several papers regarding to THD to learn more about it I noticed something strange. To be honest it seems there is AT lEAST 2 definitions for THD which are not the same!
One defination is at the begining of page #297 of this:
https://books.google.com/books?id=y...resnum=10&ved=0CF4Q6AEwCQ#v=onepage&q&f=false
The other defination is here:
https://docs.google.com/viewer?a=v&...GA_ho-&sig=AHIEtbQyYpfnDa85EGyc4f3eKdQUpGYOfg
If we suppose that the Voltage of both the fundamental frequncy and the secondharmonic for instance happens to be 4v, then for the formula of the first link the THD would be:
THD= √16/√32 =0.707 =70.7%
But regarding to the formula of the second link it would be:
THD= √16/4 =1=100%
I myself think that the formula of the second link is correct as it gives 100% of THD for when both fundamental and the second harmonic of a waveform which contains just both of them with the same amplitude would be 100% not 70.7%.
So any idea plz?
The other question is that why we must use "RMS" values of a Voltage when want to calculte the THD of a signal? You know that V1p/V2p of a signal is equal to its V1rms/V2rms. so?
Thanks