# Re: Re: Racing Spark Prediction

```Original poster: <a1accounting@xxxxxxxxxxxxx>

Hi Gerry,
>
> From: "Tesla list" <tesla@xxxxxxxxxx>
> Date: 2006/05/23 Tue AM 11:16:15 EDT
> To: tesla@xxxxxxxxxx
> Subject: Re: Re: Racing Spark Prediction
>
> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Very informative explanation of the two modes.  Are the two
> frequencies just present (sinA + sinB)

Yes they are just present. They add and therefor beat.

```
But a beat waveform can also be considered to be a sin wave amplitude modulated by an other sin wave ie sinA+sinB = SinA * sinB
```
>or do they modulate
> (sinA*sinB) and produce side bands.

```
No they do not modulate which is the equivlaent of multiplication. The voltage you measure is the sum, the addition of sinA and sinB.
```
So I was trying to explain that you can look at it in one of two ways.
Two seperate frequency components that beat. This is the usual maths way.

```
or consider it as one frequency that is modulated by the transfer of energy between the primary and secondary.
```
But not both ways at the same time.

I my thinking on this is
> admittedly loose and centered around the presence of two frequencies
> not modulating but still beating with each other and a poorly
> quenched SG allowing enough time for the two frequencies to beat with
> each other in a way maximize a voltage gradient.
>
> Gerry R.
>
>
> >Original poster: <a1accounting@xxxxxxxxxxxxx>
> >
> >HiGerry
> >snip
> > > and forth between the secondary and primary and does not decay fast
> > > enough for the beat to occur.  If this thinking is correct, maybe
> > > this explains how quenching (or lack of) can be one cause (but not
> > > the only cause) of racing arcs.  Even with perfect first notch
> > > quenching, I think, racing arcs can be caused by excessive coupling.
> > >
> > > Gerry R.
> > >
> >  You should not think about the energy of one of the modes moving
> > from primary to secondary because that is not what occurs.
> >Try this quick explanation below. I hope it helps
> >
```
> >There are two ways to think or describing how the energy sloshes back and for.
```> >One way is to think about a sin wave that starts of large in the
> >primary and is gradual transferred to the secondary and then back to
> >the primary. The energy flowing from primary to secondary and back.
> >i.e. an amplitude modulated sinwave
> >
> >Mathematically its described as two modes (the split frequencies)
> >that simultaneously oscillate in the primary and secondary. The
> >secondary phase relative to the primary is +90deg for one of the
> >modes and -90deg for the other.  Initially both modes have equal
> >(approximately) amplitude and phase in the primary.  But in the
> >secondary they are out phase by 180deg and hence cancel. So zero
> >voltage initially in the secondary.
> >
> >As time progresses because the frequencies are different for the two
> >modes the primary oscillations shift out of phase (beats) and cancel
> >so. So no voltage in the primary.
> >At that time the oscillations are in phase in the secondary and sum.
> >So the voltage in the secondary is at a max.
> >
> >In short in the two mode description of the system the mode
> >frequencies do not move from primary to secondary.
> >
> >The two ways are equivalent.  As you probably know they are linked
> >via the trig identity  sinA* sinB = sin(A-B) +sin(A+B)
> >
> >
> >
>
>
>
>
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>
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