[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Double Throw Spark Gap (fwd)
---------- Forwarded message ----------
Date: Tue, 16 Oct 2007 09:55:47 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Double Throw Spark Gap (fwd)
Exactly and my second recourse to the situation as stated. The firing is
stopped (quenched) for a time. The dead time that allows the recharge of
the entire DC circuit. And then, after recharge, your up and running!
bz-----bz-----bz, etc.
It will work Chris, I have no doubt about that. I'll be interested in
the rotational speed which you end up liking best as far as output.
Take care,
Bart
Tesla list wrote:
> ---------- Forwarded message ----------
> Date: Tue, 16 Oct 2007 21:06:37 -0500
> From: Crispy <crispy@xxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Double Throw Spark Gap (fwd)
>
> On Tue, 2007-10-16 at 19:41 -0600, Tesla list wrote:
>
>> ---------- Forwarded message ----------
>> Date: Tue, 16 Oct 2007 07:47:20 -0700
>> From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
>> To: Tesla list <tesla@xxxxxxxxxx>
>> Subject: Re: Double Throw Spark Gap (fwd)
>>
>> Hi Steve,
>>
>> I understand the large capacitance in the filter caps and stored energy.
>> My point is that the stored energy will be dissipated over time through
>> the gap and the only thing that will recharge the DC circuit is the
>> transformer. The transformer will be able to keep up with the DC current
>> requirements or it will not.
>>
>
> This is correct. And in my case, the transformer will not be able to
> keep up.
>
>
>> When you say the charging is not affected by the transformer, that is
>> partially true in that the storage caps are providing the charge to the
>> tank. But if the transformer cannot keep up, the storage cap(s) "will"
>> loose energy over time. There's no way around that except to find a
>> firing voltage in which the current required to achieve the rate of that
>> particular voltage is capable of the transformers ability or to stop
>> firing for a time to allow the recharge.
>>
>
> Actually ... there is a way around it. Allow the reservoir capacitor to
> be fully charged by the transformer, and then pulse it into the charging
> circuit in bursts, so the actual Tesla coil circuit is only connected a
> small percentage of the time. This is what we have been discussing.
>
>
>> Take care,
>> Bart
>>
>> Tesla list wrote:
>>
>>> ---------- Forwarded message ----------
>>> Date: Mon, 15 Oct 2007 23:11:10 -0600
>>> From: S&JY <youngs@xxxxxxxxx>
>>> To: 'Tesla list' <tesla@xxxxxxxxxx>
>>> Subject: RE: Double Throw Spark Gap (fwd)
>>>
>>> Bart,
>>>
>>> What you are missing in your understanding is that the DC supply has a few
>>> microfarads worth of filter or "reservoir" capacitance which allows many
>>> amps of charging current in the couple hundred microseconds of electrode
>>> presentation. So the charging current is NOT limited by the transformer
>>> current. Basically, because of the filter caps, the impedance of the power
>>> supply is MUCH lower than that of the transformer.
>>>
>>> My DC charging current is 138 mA at 8.1 kV and 200 breaks per second which
>>> yielded 78 inch streamers. Because of resonant charging, the 8.1 KV charges
>>> the MMC up to nearly twice that.
>>>
>>> --Steve Y.
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: Tesla list [mailto:tesla@xxxxxxxxxx]
>>> Sent: Saturday, October 13, 2007 11:51 AM
>>> To: tesla@xxxxxxxxxx
>>> Subject: Re: Double Throw Spark Gap (fwd)
>>>
>>>
>>> ---------- Forwarded message ----------
>>> Date: Fri, 12 Oct 2007 22:36:08 -0700
>>> From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
>>> To: Tesla list <tesla@xxxxxxxxxx>
>>> Subject: Re: Double Throw Spark Gap (fwd)
>>>
>>> Hi Bert,
>>>
>>> I don't think so. Are you saying your going to charge a 20nF cap in 69us
>>> from a 12/30 NST source? (or am I misunderstanding your derivation?). I
>>> realize the charging inductors peak current is V/sqrt(L/C), but that
>>> does not account for the impedance of the transformer. You've got 360VA
>>> to play with and nothing you do in the charging circuit is going to
>>> change that. The charging inductor and cap will require time, and with a
>>> 12/30 is going to require a lot of time. In a typical 12/30 system, a
>>> 20nF cap will require 40ms to fully charge. The charging inductor is not
>>> going to change that "unless" you have a non-limited source of current
>>> (which you don't).
>>>
>>> If I understand this scheme correctly, the charging connection is
>>> limited by the dwell time of the electrodes. That adds considerable time
>>> to the situation (it's worse than a typical AC system). There's
>>> something else which complicates the charging mechanism. If the rpm is
>>> slow, the dwell time per electrode is extended (charge will reach
>>> voltage with less passes). Increase rpm, and it will take more passes to
>>> reach breakdown desired). But, here's the gotcha, typically RSG BPS is
>>> based on timing. In this case, the gap distance becomes critical with
>>> rpm. It's an odd thing to say the least.
>>>
>>> In Steve's case, he has a hefty transformer (14/250) at 3500VA. He's
>>> using 12 electrodes at 1850 rpm with a 50nF cap. His dwell time is 470us
>>> per electrode and 5.63ms per revolution. When you factor in the
>>> impedance of the transformer, full charge time is 64.3ms. This will
>>> require 11.4 revolutions to fully charge the cap. He's running at 370
>>> ppr, but if he was to actually fire at 30KVDC, the actual firing bps
>>> would only be 32 (by my calculation). He is likely firing at about
>>> 17KVDC which is in the low 100 bps range and likely brought about by gap
>>> distance, electrode edge surface, etc.). Gap distance is going to play a
>>> significant role in these SPDT gaps.
>>>
>>> In Chris's case, there's a huge difference (3,140 VA).
>>>
>>> Take care,
>>> Bart
>>>
>>>
>>>
>>> Tesla list wrote:
>>>
>>>
>>>> ---------- Forwarded message ----------
>>>> Date: Tue, 09 Oct 2007 23:10:39 -0500
>>>> From: Bert Hickman <bert.hickman@xxxxxxxxxx>
>>>> To: Tesla list <tesla@xxxxxxxxxx>
>>>> Subject: Re: Double Throw Spark Gap (fwd)
>>>>
>>>> Hi Adam,
>>>>
>>>> I suspect the tank cap will charge almost completely. Let's plug in some
>>>> reasonable "guesstimate" numbers and see...
>>>>
>>>> Chris didn't indicate the size of his tank cap, so let's take an
>>>> educated guess that it's 0.02 uF. We can always change this to the
>>>> actual cap size Chris is using later if necessary. The starting voltage
>>>> on the DC storage cap (when driven by a 12/30 NST and FWB rectifier)
>>>> will be about 17,000 volts. With a 25 mH charging choke, the resonant
>>>> charging frequency of the combination of the charging choke (Lc), tank
>>>> cap (Cp), and DC storage cap (Cs) will be about 7300 Hz. If allowed to
>>>> fully complete, the charging current will be a half sine wave lasting
>>>> for 1/2 cycle, or about 69 usec, peaking at about 14.5 amperes. For
>>>> complete resonant charging cycle, we must see a minimum effective dwell
>>>> time of about 69 usec in th charging gap.
>>>>
>>>> Now, when the charging gap initially fires, the rotating contacts are
>>>> approaching each other. Let's assume that the gap fires when the
>>>> approaching electrodes reach a minimum separation of 0.25", the gap
>>>> electrodes are 0.125" in diameter, and the DC charging current arc can
>>>> be drawn out at least another 0.375" before being extinguished. YMMV.
>>>> With these parameters, the estimated total distance over which the
>>>> charging current would be connected (via arcing) would be about 0.75".
>>>>
>>>> Let's further assume that the ARSG rotor speed is 3000 RPM, and the
>>>> electrode radius of rotation is 4" (8" diameter for electrode rotation).
>>>> The effective "dwell" angle is about 10.7 degrees, and at 3000 RPM this
>>>> translates to about 42 usec of total effective dwell time versus 69 usec
>>>> to fully charge the tank cap. Does this mean that the gap will
>>>> prematurely interrupt the charging cycle?
>>>>
>>>> I suspect the answer is - NO.
>>>>
>>>> Since the peak charging current is a robust 14.5 amps, I suspect that
>>>> (at least for the relatively short arc distances we're discussing) the
>>>> gap will be unable to interrupt the charging cycle until the charging
>>>> current has dropped significantly - perhaps down to an ampere or less.
>>>> Instead of prematurely terminating the charging cycle, I suspect that
>>>> we'll see trailing arcs in the gap that effectively "stretch out" the
>>>> dwell time so that the tank cap can achieve nearly 2 x Vsupply.
>>>>
>>>> It will be interesting to see the actual results that Chris sees... :^)
>>>>
>>>> Bert
>>>>
>>>> Tesla list wrote:
>>>>
>>>>
>>>>
>>>>> ---------- Forwarded message ----------
>>>>> Date: Tue, 9 Oct 2007 03:46:42 -0700 (PDT)
>>>>> From: Yurtle Turtle <yurtle_t@xxxxxxxxx>
>>>>> To: tesla@xxxxxxxxxx
>>>>> Subject: Double Throw Spark Gap
>>>>>
>>>>> I haven't really been following this thread, so
>>>>> forgive me if this comment has already been addressed.
>>>>>
>>>>>
>>>>> Regarding the following circuit:
>>>>>
>>>>> http://tangent.cluenet.org/~chules/hv/tesla/dtsg.html
>>>>>
>>>>> Does everyone think the cap can charge adequately in
>>>>> the same amount of time it can discharge? Without
>>>>> doing the math, I gotta believe that if one set of
>>>>> flying electrodes zooms around at several hundred rpm,
>>>>> the presentation time for the charging portion will be
>>>>> too short to fully charge the cap. After all, most rsg
>>>>> coils are charging the whole time they aren't
>>>>> presenting (well not exactly). I guess you gotta know
>>>>> the dwell time and the size of the pig feeding this.
>>>>>
>>>>> Adam
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>> ____________________________________________________________________________
>>> ________
>>>
>>>
>>>>> Boardwalk for $500? In 2007? Ha! Play Monopoly Here and Now (it's updated
>>>>>
>>>>>
>>> for today's economy) at Yahoo! Games.
>>>
>>>
>>>>> http://get.games.yahoo.com/proddesc?gamekey=monopolyherenow
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>
>
>
>