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Re: [TCML] The truth about LTR, STR, and resonant modes
In addition to tuning the cap, we also tune the ballast and power supply
with pole xmfrs to deliver the most efficient amount of current into the
system for optimum spark production at any given voltage setting. We "dip"
the supply current using our ballast control, and when the power factor is
corrected back to 1.0 then you have max efficiency. Longer sparks occur
when this setting is pushed up 10% but this does draw more current. Very
similar to tuning a ham radio transmitter in which the operator "dips" the
plate current to find the best resonant point before pushing higher power
into the system. To do this properly one needs a power factor meter,
however, lacking one, you can also do it by carefully monitoring your "plate
current" and then adding 10% after the dip.
Similar to what John is discussing.
Dr. Resonance
On Wed, May 28, 2008 at 12:34 PM, <Mddeming@xxxxxxx> wrote:
>
> Hi John,
>
> Exceptional clarity and conciseness. You definitely learned your writing
> skills in the era before text-messaging. ;^)
>
> Matt D.
>
> In a message dated 5/28/08 2:21:00 A.M. Eastern Daylight Time,
> FutureT@xxxxxxx writes:
>
> In a message dated 5/27/08 6:21:03 PM Eastern Daylight Time,
> FutureT@xxxxxxx
>
> writes:
>
> > >If a pig or PT coil is run with a small
> > >cap at high bps, then the ballast L has to be reduced to let in
> > >more power (if long sparks are desired). Then the coil is truly
> > >running in STR mode.
> >
> > >John
> >
>
> Correcting my post above here. Such a coil as above
> (small cap, high bps), is not necessarily STR mode.
> This can be resonant or LTR mode also. It all depends on
> the ballast setting (explained below). My other recent posts
> mostly spoke of 120 bps operation but the comments
> in those posts
> apply to higher bps operation also, except the power
> factor might not be as good at the higher bps.
>
> Deano is most likely correct that most folks are
> probably running in resonant mode with their pig and
> PT systems. Resonant mode is not solely dependent
> on the cap value for a given non-shunted transformer.
> Any cap value can be run in LTR, STR, or resonant
> mode by adjusting the ballast as needed to give the
> respective mode. This is mostly independent of
> the transformer size (within reason of course). A
> too large cap will not be able to be charged to
> a reasonable voltage, etc.
>
> NST's (and OBITS), i.e. shunted, transformers are a
> special case. For a given NST, a given cap value is
> either LTR, STR, or resonant. This is not true for
> unshunted transformers such as pigs and PT's. These
> transformers are always run with a ballast. The
> setting of the ballast will determine, along with the
> cap value, whether the system is running in LTR,
> STR, or resonant mode. The transformer doesn't
> really enter into the equation except for impedance
> transformation which determines how much ballast
> L is needed for a particular mode, and also the
> transformer must be able to handle the power, etc.
>
> It's not correct to say, "this pig has an LTR
> value cap" or something similar. The cap itself
> doesn't determine if the system is running in LTR
> mode. This will be determined by the setting of
> the ballast also. Of course the spark length has to
> be considered. Longest sparks may be produced
> in resonant mode, or slightly LTR. In resonant
> mode, the reactance of the ballast "cancels" the
> reactance of the cap, and this lets the maximum
> power enter the system. This should give longest
> sparks. LTR may work somewhat similarly up to
> a point. There are issues such as inductive kick
> to consider. As the ballast is increased in
> inductance, this will create an LTR mode in
> high bps systems, but it will also tend to
> throttle back the power and reduce the spark
> lengths.
>
> Coilers should select their cap value based on
> the needed spark length, and the capabilities of
> the transformer. If the transformer is extra powerful,
> they can select a smaller cap, and adjust the
> ballast for resonance or LTR and still get rather
> short sparks if that's what they want. If they
> want longer sparks, then just use a larger cap,
> and again adjust for resonance or slight LTR. If one wants
> super long sparks, then use an even larger
> capacitor and again adjust for resonance or
> slight LTR. This may force the pig to provide
> double its rated power, but pigs can handle that.
>
> Folks used to talk a lot about each coil having
> its own personality so to speak. I believe one
> cause of that was the relative cap value versus
> the transformer power versus the ballast setting,
> thereby making the coil run either LTR, STR, or
> resonant. I used to often talk about how
> important it is to use the proper value cap for
> 120 bps coils, but the proper value cap is
> important for high bps coils too, so that the
> spark lengths will be correct, when the ballast
> is set (tuned) correctly. This is what Bill Wysock
> talks about when he talks about tuning the ballast.
> This is probably creating a resonant or slight LTR
> condition for maximum efficiency and best power
> factor. I'm not sure exactly what adjustment
> (LTR, STR, or resonant) will give best power factor
> with high bps, but surely one of them will be best
> in that regard.
>
> In some cases folks may use a capacitor that
> is larger than optimal for the desired spark length.
> This may make it necessary to misadjust the
> ballast and introduce inefficiency or a bad power
> factor into the system to deliberately reduce the
> spark length.
>
> Some may say that fixed LTR, STR, and resonant
> cap values are valid for pigs and PT's. This
> may be true if the transformer is run at its
> rated power. But if it's not run at it's rated power,
> if it's run at either higher or lower power, then
> the LTR, STR, and resonant values change.
> This is why it's best to look at it from both
> and cap value *and* ballast inductance value
> perspective. Otherwise the situation can be very
> misleading.
>
> I hope the above is written clearly enough.
> I kind of jumped around with the thoughts.
>
> John
>
>
>
>
>
>
>
>
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