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Re: [TCML] Series Transformers

To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Subject: Re: [TCML] Series Transformers
From: "Phillip Slawinski" <pslawinski@xxxxxxxxx>
Date: Wed, 18 Jun 2008 20:47:57 -0500
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Has anyone made a spark gap tesla coil with such a low voltage and high
current?  Is there a way to make a sort of solid state spark gap?  Of course
without all the complicated circuitry of a DRSSTC.

On Wed, Jun 18, 2008 at 7:37 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:

> It probably could be done with a rotary, but it would certainly be an
> unconventional rotary. A sucker gap is good, but at the large cap size
> discharge energy, it's likely to be a problem. And due to the low voltage,
> increasing electrodes within the sucker gap has the same problem as the
> rotary. This is also not a good system for a standard hyperbaric gap.
> Hmmm..... Well, maybe a large surface area quench gap would work?
>
> An interesting problem! SISG comes to mind for some odd reason  ;-) .
>
> Bart
>
>
> Lau, Gary wrote:
>
>> My experience to date has been strictly with NST's, so take what I say
>> with a grain of salt.  But the experience of others as reported on this List
>> is that static gaps perform poorly with high current transformers.  Yes, I
>> suspect that quenching will be the issue.
>>
>> I would fear that a rotary gap would need its electrodes set precariously
>> close, especially since the total gap needs to be divided into two segments.
>>  But you didn't hear me say that it can't be done!
>>
>> Regards, Gary Lau
>> MA, USA
>>
>>
>>
>>> -----Original Message-----
>>> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
>>> Behalf Of Phillip Slawinski
>>> Sent: Wednesday, June 18, 2008 8:11 AM
>>> To: Tesla Coil Mailing List
>>> Subject: Re: [TCML] Series Transformers
>>>
>>> I have already built a sucker gap, and it seemed to do a decent job
>>> quenching.  This of course was with a .013 mfd cap.  I suppose when the
>>> full
>>> 1mfd + cap is hooked up the quenching will worsen?  Why do you say a
>>> rotary
>>> gap is probably not advisable, electrode spacing has to be too close for
>>> comfort?
>>>
>>> On Wed, Jun 18, 2008 at 6:41 AM, Lau, Gary <Gary.Lau@xxxxxx> wrote:
>>>
>>>
>>>
>>>> 2970V @800mA will be challenging.  Despite many who thought 4kV is too
>>>> low
>>>> for a coil, I built a very efficient coil using a 4kV/20mA NST, using a
>>>> single static cylinder gap.  While it may be possible to get a static
>>>> gap to
>>>> work at 2970V, the 800mA part may be difficult to quench.  At that low a
>>>> voltage, an RSG is probably not advisable.  You would also need a very
>>>> large
>>>> cap to utilize the full potential of that power supply.
>>>>
>>>> Regards, Gary Lau
>>>> MA, USA
>>>>
>>>>
>>>>
>>>>> -----Original Message-----
>>>>> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
>>>>> Behalf Of Phillip Slawinski
>>>>> Sent: Tuesday, June 17, 2008 9:21 PM
>>>>> To: Tesla Coil Mailing List
>>>>> Subject: Re: [TCML] Series Transformers
>>>>>
>>>>> I have a nice variac 20A rated and 0-270V output with 120V in.  I was
>>>>>
>>>>>
>>>> able
>>>>
>>>>
>>>>> to wire them in series and ran them up to 2970V @ 800mA.  Is 2970V too
>>>>>
>>>>>
>>>> low
>>>>
>>>>
>>>>> to run a TC efficiently?
>>>>>
>>>>> On Tue, Jun 17, 2008 at 5:13 PM, David Speck <Dave@xxxxxxxxxxxxxxxx>
>>>>>
>>>>>
>>>> wrote:
>>>>
>>>>
>>>>> OK, Phil,
>>>>>>
>>>>>> Looks to me like you want to step 110 VAC to perhaps 1100 VAC.
>>>>>>
>>>>>> If they are identical transformers, then their internal polarities are
>>>>>> probably the same.  (But you can't count on that!)
>>>>>>
>>>>>> Wire the two primaries in parallel.  Connect the high voltage output
>>>>>>
>>>>>>
>>>>> end of
>>>>
>>>>
>>>>> one transformer secondary to the low voltage end of the other
>>>>>>
>>>>>>
>>>>> secondary.
>>>>
>>>>
>>>>>  Power up the pair with a Variac set on a very low voltage, say one
>>>>>>
>>>>>>
>>>>> volt.
>>>>
>>>>
>>>>>  Measure the voltage from the low end of the first transformer
>>>>>>
>>>>>>
>>>>> secondary to
>>>>
>>>>
>>>>> the high end of the second transformer secondary.  If you have the
>>>>>> connection right, then you should see something like 11 volts.  You
>>>>>> can
>>>>>>
>>>>>>
>>>>> then
>>>>
>>>>
>>>>> crank up the Variac voltage slowly to confirm that you see a
>>>>>>
>>>>>>
>>>>> corresponding
>>>>
>>>>
>>>>> increase in the output voltage at the high end.  Remember that Variacs
>>>>>>
>>>>>>
>>>>> do
>>>>
>>>>
>>>>> not provide any line isolation, and even at a one volt output, the
>>>>>>
>>>>>>
>>>>> "hot" end
>>>>
>>>>
>>>>> of the Variac output is still at line potential and can deliver a
>>>>>>
>>>>>>
>>>>> lethal
>>>>
>>>>
>>>>> shock.
>>>>>> If you don't see any voltage, check the output across each of the
>>>>>> transformers, to make sure that one of them is not open.  If both are
>>>>>> putting out about 5.5 volts individually, then you have the
>>>>>> secondaries
>>>>>> connected wrong.  Just swap the link between the two secondaries to
>>>>>> the
>>>>>> opposite secondary pin on one transformer (with the power off!) and
>>>>>>
>>>>>>
>>>>> recheck.
>>>>
>>>>
>>>>> A small word of warning -- many digital voltmeters (both cheap and
>>>>>> expensive) can give spurious readings when used to measure unloaded
>>>>>> transformers.  You may get much more sensible readings if you parallel
>>>>>>
>>>>>>
>>>>> a 1K
>>>>
>>>>
>>>>> to 10K ohm power resistor across the inputs to your voltmeter.  I once
>>>>>> wasted a half a day trying to figure out the transformer of a bandsaw
>>>>>>
>>>>>>
>>>>> blade
>>>>
>>>>
>>>>> welder with a good Fluke DVM.  The readings were all over the map, and
>>>>>>
>>>>>>
>>>>> often
>>>>
>>>>
>>>>> inconsistent and unrepeatable.  Putting a load resistor on the meter
>>>>>>
>>>>>>
>>>>> made
>>>>
>>>>
>>>>> everything work out sensibly.
>>>>>> 1100 VAC isn't going to help you a lot for TC work.  You might be able
>>>>>>
>>>>>>
>>>>> to
>>>>
>>>>
>>>>> get away with seriesing 4 transformers for 2200 volts, but at this
>>>>>>
>>>>>>
>>>>> point,
>>>>
>>>>
>>>>> you will begin to stress the insulation between the windings and the
>>>>>>
>>>>>>
>>>>> cores.
>>>>
>>>>
>>>>>  I've read of 4 and 6 MOT series strings, but the outer transformers on
>>>>>>
>>>>>>
>>>>> the
>>>>
>>>>
>>>>> 6 MOT strings had to be run under transformer oil to prevent winding to
>>>>>>
>>>>>>
>>>>> core
>>>>
>>>>
>>>>> voltage breakdown.  OTOH, the power output of a 6 MOT string (~12 KVAC
>>>>>>
>>>>>>
>>>>> at
>>>>
>>>>
>>>>> 500 mA, if you use big MOTs), can compare favorably with a 5 KVA pole
>>>>>>
>>>>>>
>>>>> pig,
>>>>
>>>>
>>>>> just not so nice and compact, but nearly free, if you can find the
>>>>>>
>>>>>>
>>>>> MOTs.
>>>>
>>>>
>>>>> HTH,
>>>>>> Dave
>>>>>>
>>>>>>
>>>>>> Phillip Slawinski wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>> Step Down transformers run in reverse.  The transformers have taps
>>>>>>> for
>>>>>>> neutral 100V 110V on the primary.  On the secondary neutral  420 480
>>>>>>>
>>>>>>>
>>>>>> 550.
>>>>
>>>>
>>>>> On Tue, Jun 17, 2008 at 1:39 PM, David Speck
>>>>>>>
>>>>>>>
>>>>>> <Dave@xxxxxxxxxxxxxxxx>
>>>
>>>
>>>> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Phil:
>>>>>>>>
>>>>>>>> What kind of transformers?
>>>>>>>>
>>>>>>>> You can't series NSTs, 'cause they are center tap grounded.  You can
>>>>>>>> parallel them for more current, though.
>>>>>>>>
>>>>>>>> Dave
>>>>>>>>
>>>>>>>> Phillip Slawinski wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>> Does anyone know of a way to wire two transformers so that they are
>>>>>>>>> oppositely phased?
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>  _______________________________________________
>>>>>>>
>>>>>>>
>>>>>> Tesla mailing list
>>>>>> Tesla@xxxxxxxxxxxxxx
>>>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>>>
>>>>>>
>>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>>
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>>>>
>>>>
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>>
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Follow-Ups:
- Re: [TCML] Series Transformers
  - From: weston braun

References:
- [TCML] Series Transformers
  - From: Phillip Slawinski
- Re: [TCML] Series Transformers
  - From: David Speck
- Re: [TCML] Series Transformers
  - From: Phillip Slawinski
- Re: [TCML] Series Transformers
  - From: David Speck
- Re: [TCML] Series Transformers
  - From: Phillip Slawinski
- RE: [TCML] Series Transformers
  - From: Lau, Gary
- Re: [TCML] Series Transformers
  - From: Phillip Slawinski
- RE: [TCML] Series Transformers
  - From: Lau, Gary
- Re: [TCML] Series Transformers
  - From: bartb

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