Re: [TCML] how to work out average current ?

["Tim Meehan" <btmeehan@xxxxxxxxx>]

I got 0.142 amperes (rms) for your waveform, which sounds like more than
your current limit.  If you ignore the fact that the waveform alternates
with positive and negative pulses, and only average the current over the
triangular shape and include the time up to but not including the next
(negative current) pulse, I got an average current of 0.0275 (but I'm not
sure that you can use that for your current limiting calculations - I think
that the rms value is what you want).

The rms calculation was:
Sqrt[Integrate[(1.1-1.1/(500e-6)t)^2, {t,0,500e-6}]/0.010]

The average value calculation for one cycle was:
Integrate[1.1-1.1/(500e-6)t, {t,0,500e-6}]/0.010

On Nov 17, 2007 1:37 PM, Chris Swinson <list@xxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:

> Hi Tim,
>
> > Hi Chris - I'm not sure which of the waveforms was your current
> waveform.
> > I
> > think that it was the turquoise one.  I see up and down spikes, but from
>
> yes you guessed right, it was the triangle shaped one. spikes to about
> 1.1Amps and slowly drops over about 500uS or so.
>
>
>
> > what I could tell - the time between the up spike and the down spike is
> 10
> > miliseconds.  If the current waveform is truly just as much above 0 amps
> > as
> > it is below 0 amps - the average current would be 0 amps.  If you wanted
> > to
> > find the root mean square current, that can also be done semi-easily.
>
> Well true the pulse is pos and neg, I am just thinking towards a single
> cycle..
>
>
> >
> > I'm just not particularly familliar with the type of coil you are making
> -
> > or I would be able to probably just give you the answer ...
> >
>
> Its just a DC res-charge design. the current is AC amps form the NST
> secondary. As I can't draw 1.1Amps form the secodnary, it will be limited
> to
> about 100mA so it would take maybe 10times longer to charge...
>
>
>
> > Since you have a simulator, you may also be able to save the current
> > waveform to a text file of some sort.  You could send the file to me and
> I
> > will integrate it for you - or I could help you write a formula for a
> > spreadsheet program to do it.  I do this sort of stuff all the time and
> > I'd
> > be happy to do it for you ...
> >
>
> The current waveform is the turquoise one... really out of a 50hz wave you
> are only looking at really 1 fully AC cycle in total. I could overlay the
> AC
> waveform.. the tank volts is the red line running at 400hz..
>
>
>
> > For the average current, you integrate it and divide by the length of
> the
> > waveform (in time).
> >
> > For the root mean square current, you square each 'y' value, integrate
> the
> > waveform, divide by the length in time, then you take the square root of
> > that value.
> >
> > If your waveform has bipolar pulses (just as many positive current as
> > negative current) you'll need to do the RMS method.
>
> The RMS way the simulate calculates it as 150mA.. I know 80mA limited via
> a
> resistor will *just* charge up in between each mains cycle. So 100mA
> should
> be about the right figure.. each 50mA though is an addition of another
> NST.
> so just trying to work out what would fit.. The figure has to be between
> 80mA and 150mA so maybe 100mA is the way to go...
>
> Chris
>
>
>
>
>
>
>
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