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Re: [TCML] PFC Question (again)--more
This is another reason why even pole xmfrs should have some transient
protection. I use a network of 12 parallel resistors, 600 Ohms each, 200
Watts, in series with the output. After the resistor network I always use a
3" ID x 10" long air core choke wound with #14 600 volt PVC wire. This is
insulated from ground on a pair of stand-off insulators. I have this data
in schematic form is anyone should need it.
I know many people don't but good engineering practice dictates they
should. Even robust pole xmfrs don't like harsh transients for long periods
of time. Lightning strikes, by contrast, are very short duration as
compared to running a xmfr for 1-2 minutes.
Dr. Resonance
On Wed, May 28, 2008 at 10:00 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:
> Hi John,
>
> Your right. The inductive ballast on PIGs and PTs do change the LTR/STR
> scenario. I however always look at this as based on the transformer alone.
> But your right, the ballast changes that scenario. Even though JAVATC states
> that LTR is intended for internally ballasted transformers such as NST's, I
> still personally look at LTR as a general transformer situation (which I
> probably should not). You've done well to point out the issues. This isn't
> the first time! We've been down this road in the past as you know. I agree
> with all you've said in this post and in the other posts that I missed out
> on replying (had to take wife to hospital the last couple days, so TCML was
> just not possible).
>
> Anyway, great postings on this subject. I could not agree more. But I will
> say that all of us (you included) really don't know if PIG's are truly
> running LTR, STR, near or at resonance. I've always assumed STR given my
> personal situation and how I likely relate to the coiling world. The fact
> is, we might be running STR. When you hit that STR value near 1.4, your
> basically riding the edge of resonance, but just enough to allow a little
> voltage calming. Were all likely hitting that area. I honestly doubt LTR in
> pig (just a hunch). Not just from a massive cap size scenario or even the
> ballast inductive affect on what is or is not LTR, but the fact that when
> you run a coil in slight resonant charge mode (always near resonance in
> either direction), there are always some good sparks to be realized if
> there is sufficient "power" regardless.
>
> I run STR on a small coil and get great spark lengths, but I have the power
> in the transformer to make it happen. This would not have been possible if
> the coil was not running near resonance at a 1.4 ratio. Well, maybe I speak
> too soon. I haven't tried a larger ratio and maybe I should. But, it does
> incredible for it's situation. Who's to say that Kevin's larger coil would
> not do as well scaled appropriately. That is my rub. Even though PIG's and
> PT's are externally ballasted (not always), doesn't indicate that they must
> be running LTR. They can certainly be running well in STR mode as well. BPS
> is certainly part of their efficiency, but when it comes to power and
> sparks, efficiency isn't always the winner. Considering the costs and size
> of components, it's probably economical to do the great spark lengths
> inefficiently. I hate to say that (as I'm into alternative energies and the
> like), but the cost of reality probably dictates that situation more than
> anything else.
>
> My bottom line is that I'm not sure and I'm pretty sure no one else is
> either. If I had the resources and funds, I would strive for efficiency in
> spark length. I know you would also. We all would if we could.
>
> Bart
>
> FutureT@xxxxxxx wrote:
>
>> In a message dated 5/27/2008 4:22:54 P.M. US Eastern Standard Time,
>> FutureT@xxxxxxx writes:
>>
>>
>>
>>> David,
>>>
>>>
>>
>>
>>
>>> I didn't do the calcs lately but I think it's close to resonant,
>>> maybe slightly LTR. He's running at 120 bps. At 120 bps,
>>> you pretty much have to use resonant or LTR to get good power
>>> throughput.
>>>
>>
>>
>>
>>> John
>>>
>>>
>>
>>
>> Also (adding to my posting here). Resonant and LTR have a
>> different meaning for pig and PT coils than for NST coils. For an NST
>> coil the resonant sized cap or LTR value cap is
>> a certain value. For a pig or PT coil, the setting of the ballast
>> determines if the coil operates in STR, resonant, or LTR mode.
>> At the pig or PT's rated power, there may be a particular value
>> cap for LTR or resonant. But such a coil can be run at more
>> or less than it's rated power. For example at 120 bps, a small cap could
>> be
>> installed on a pig coil, a certain amount of ballast can be cranked
>> in to make it resonant, and it will run, but at less than the
>> transformer's rated power. For example let's say the resonant
>> value is 0.3uf. A cap of only 0.03 can be installed, and the correct
>> amount of ballast can be cranked in to give resonant operation,
>> and the coil will run. It won't draw much power, and sparks will
>> be short, but it will be running in resonant mode. Also an "LTR"
>> value cap can be installed on the pig coil, and the needed ballast
>> can be cranked in to give resonant operation. Perhaps the
>> transformer will draw twice it's rated power, but it will still be
>> able to operate in resonant mode, despite having an "LTR" value
>> cap. Sparks will be very long in this case. In any case resonant
>> operation depends a lot on the ballast setting for pig and PT coils,
>> unlike for NST coils which have a fixed leakage inductance, and
>> a fixed resonant cap value. 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
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> **************Get trade secrets for amazing burgers. Watch "Cooking with
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