Re: mysterious coil failure / M and k Measurement (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Wed, 31 Oct 2007 10:19:14 -0600
From: resonance <resonance@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: mysterious coil failure / M and k Measurement (fwd)



We use an electric hot water heater element (about $5 at any local 
hardware).  We always set our current at a steady 10 Amps and then read the 
milliVolts on the secondary.  No changes in the reading and very accurate 
method.

Dr. Resonance

Resonance Research Corp.
www.resonanceresearch.com


----- Original Message ----- 
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, October 31, 2007 8:25 AM
Subject: Re: mysterious coil failure / M and k Measurement (fwd)


>
> ---------- Forwarded message ----------
> Date: Wed, 31 Oct 2007 07:02:14 +0100
> From: Kurt Schraner <k.schraner@xxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: mysterious coil failure / M and k Measurement
>
> The safety concerns, regarding the circuit at Bart's site:
> http://www.classictesla.com/download/M_and_k_Measurement.gif
> can be eliminated, using a downstep transformer (i.e. Vout=6...12V; some
> Amps), inserted between the mains AC line and the rest of the circuit. And
> voltage may optionally be adjusted, by using a variac. This allows much
> quicker measurement at different taps of the primary.
> BTW, I'm also taking the measurements without the RC combination accross 
> the
> secondary.
>
> Regards, Kurt
>
>
> Tesla list wrote:
>> ---------- Forwarded message ----------
>> Date: Mon, 29 Oct 2007 13:04:46 +0000
>> From: "Lau, Gary" <Gary.Lau@xxxxxx>
>> To: 'Tesla list' <tesla@xxxxxxxxxx>
>> Subject: RE: mysterious coil failure (fwd)
>>
>> One doesn't need a signal generator or scope of any kind to measure
>> coupling.  You need only know the primary and secondary inductance,
>> and perform the measurement described at
>> http://www.classictesla.com/download/M_and_k_Measurement.gif
>>
>> I've not found it necessary to include the RC network across the
>> secondary.  The wording is confusing with "Take concentric readings
>> from meters."  I think what was meant is to take both primary current
>> and secondary voltage measurements at the same time on separate
>> meters.
>>
>> Regards, Gary Lau
>> MA, USA
>>
>>> From: resonance <resonance@xxxxxxxxxxxx>
>>> To: Tesla list <tesla@xxxxxxxxxx>
>>> Subject: Re: mysterious coil failure (fwd)
>>>
>>>
>>>
>>> You need to check your coeff. of coupling and usually keep it below
>>> 0.12 for most classic spark gap coils.  Some of my coils run best
>>> with greatest spark output at .08 to 0.1 range.  A local Univ. or
>>> tech college with a storage scope and sig gen can help you do this.
>>> The equations and procedures are in the Tesla List Archives.
>>>
>>> If your coeff. of coupling is producing a "double hump" then your
>>> coupling is too tight, energy is being wasted, and your coil will
>>> hit HV peaks at two points --- sometimes not at the end of the sec.
>>>
>>> This produces tracking and eventually destruction of the coil.
>>>
>>> Also, be sure to always sand both interior and exterior of any
>>> coilform prior to winding.  Also use some small acrylic baffles
>>> approx 6-8 inches down from each end in the sec.  Silicone into
>>> place with GE Silicone II  --- available at most hardware stores.
>>>
>>> Dolph's AC-43 has much greater anti-tracking properties than
>>> polyurethane, and it's price is reasonable if you consider the
>>> amount of repair time that is required when a coil fails.
>>>
>>> Dr. Resonance
>>>
>>> Resonance Research Corp.
>>> www.resonanceresearch.com
>>>
>>>
>>> ----- Original Message -----
>>> From: "Tesla list" <tesla@xxxxxxxxxx>
>>> To: <tesla@xxxxxxxxxx>
>>> Sent: Sunday, October 28, 2007 8:03 PM
>>> Subject: RE: mysterious coil failure (fwd)
>>>
>>>
>>>
>>> ---------- Forwarded message ----------
>>> Date: Sun, 28 Oct 2007 19:50:56 -0400
>>> From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
>>> To: Tesla list <tesla@xxxxxxxxxx>
>>> Subject: RE: mysterious coil failure (fwd)
>>>
>>>
>>> Thanks guys,
>>>      I don't think it was a shorted turn, there is no carbon on the
>>> inside but there is a tiny black spot on the outside (I don't use
>>> end caps on my coils, is this bad?).  I attach my RF ground by a
>>> copper strap, soldered onto the end of the bottom turn, I think it
>>> arced from the sharp edge of the strap to the wire above it (turn
>>> 2).  This occurred underneath of the several layers of electrical
>>> tape coated with polyurethane insulation on the bottom.  One other
>>> detail I forgot to mention, I set the coupling as high as I could
>>> get it that night to make up for decreased performance
>>> from wind and humidity, so that may have contributed.  I'll sand her
>>> down and rewind the bottom and see if it works again, thanks guys.
>>>
>>> Scott Bogard.
>>>
>>>> Date: Sun, 28 Oct 2007 11:07:40 -0700
>>>> From: tesla@xxxxxxxxxx
>>>> To: tesla@xxxxxxxxxx
>>>> Subject: Re: mysterious coil failure (fwd)
>>>>
>>>>
>>>> ---------- Forwarded message ----------
>>>> Date: Sun, 28 Oct 2007 11:01:32 -0800
>>>> From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
>>>> To: Tesla list <tesla@xxxxxxxxxx>
>>>> Subject: Re: mysterious coil failure (fwd)
>>>>
>>>> Hi Scott,
>>>>
>>>> Yes, the glowing spot is either a shorted turn or carbon track. It
>>>> may be a shorted turn and easy to fix if right on the bottom, and
>>>> "if" it is like the very bottom turn, it's probably too much power
>>>> for too long a period. I've had this happen on my 4" coil even with
>>>> low coupling. If enough power is provided, it can cause extensive
>>>> heating a greatest heating on the bottom of the secondary (highest
>>>> current). If you were to continue running it, a nice little fire
>>>> will begin. If it's a shorted turn, you'll have a nice black carbon
>>>> ring around the entire turn. Real easy to fix obviously.
>>>>
>>>> Take care,
>>>> Bart
>>>>
>>>> Tesla list wrote:
>>>>> ---------- Forwarded message ----------
>>>>> Date: Sat, 27 Oct 2007 22:10:06 -0400
>>>>> From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
>>>>> To: tesla@xxxxxxxxxx
>>>>> Subject: mysterious coil failure
>>>>>
>>>>>
>>>>> Hey guys,
>>>>>      I was running my 6-in MOT coil tonight for my little cousins,
>>>>> and it
>>>>> died and I cannot figure out what is wrong.  The spark gap fires
>>>>> fine, I did not adjust anything, it just died between runs, and
>>>>> won't arc except to a grounded rod (it acts like it is badly out
>>>>> of tune, but like I said,
>>>>> I adjusted nothing).  The only thing different I notice, is that
>>>>> there was
>>>>> very high humidity, and I could see a tiny spark at the base of the
>>>>> secondary.  It isn't arcing to anything, it is just a glowing
>>>>> spot, that melted through the electrical tape insulation.  I'm
>>>>> stumped, I guess I'll
>>>>> tear the insulation off of the bottom of the sec' coil and see if
>>>>> anything
>>>>> is amiss, but I've never had a failure like this before.  The only
>>>>> other possibility is that somehow my ballast malfunctioned, but I
>>>>> don't think so.
>>>>>
>>>>> Scott Bogard.
>>>>>
>>>>>
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>>>>>
>>>>>
>>>>
>>>>
>>>>
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