[R-390] Ballastubes (was inrush current limiters)

[Cecil Acuff]

Greetings all,

        I agree with you Drew.....a half wave rectified sine wave has the
same peak value as a the original sine wave....but not the same peak to peak
value.  The peak value of a sine wave is half it's peak to peak value.  You
ended up with the peak value by stripping off the top half of the wave form
with the half wave rectifier.  So you have satisfied the first part of the
formula...you divided by 2. Now you multiply by .707 and you have RMS.

The formula in my books say to arrive at the RMS value of a sine wave you
divide it's Peak to Peak value by 2 to arrive at Peak value then multiply
that Peak value by .707 and you have RMS.

I agree the .5 value is probably for a square wave.

Go to google and search on Root Mean Squared....go to the last link listed
if I remember correctly and it covers it pretty well.

Cecil...
----- Original Message -----
From: Drew Papanek <drewmaster813@hotmail.com>
To: <R-390@mailman.qth.net>
Cc: <chacuff@cableone.net>
Sent: Tuesday, December 24, 2002 3:37 PM
Subject: Re: [R-390] Ballastubes (was inrush current limiters)


> On Mon, 23 Dec 2002 21:58:34 -0600, Cecil Acuff wrote:
>
> <snip>
>
> >An AC waveform is a Peak to Peak waveform.  Moving equal amounts above
and
> >below Zero.  (in this case)
> >
> >You arrived at peak value by half wave rectifying the Peak to Peak sine
> >wave.
>
> Half wave will posess the same (neglecting diode drop) peak value as the
> symmetrical sinewave whence it came, but a half sinewave is not the same
> waveform as a full sinewave.
>
> >You now multiply that value by .707 to get the RMS value.  To go from
> >RMS back to Peak you multiply by 1.414 and then double that to get Peak
to
> >Peak values.
>
> This applies to a full sine wave, but not a half sine wave.  Yes, the RMS
> value of a sine wave is .707 times its peak value.  However, the RMS value
> of a half sinewave is .5 times its peak value.
>
> Drew
>
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