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

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 01 Nov 2007 18:13:59 -0800
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: mysterious coil failure / M and k Measurement (fwd)

Hi Gary & Kurt,

Sounds like a safe means of performing the measurement. Like Kurt, I 
rarely do this anymore and use Javatc for the value (which is the same 
code used in ACMI for those particular outputs). This is the safe method 
in my book. Enough coilers have verified accuracy time and time again. 
Programs also handle the inductances.

In practice, coilers want to measure for themselves from time to time 
and are going to do so with the method easiest to perform (which is this 
one). This test will put ~120 Vac on the exposed primary winding and 
there are other numerous cords and connections which are hot lying 
around as well (and are more likely to get a shock from those 
connections than anything else).

Coilers performing the test are going to have to be careful to make sure 
they don't fall or grab an exposed hot wire, primary, etc. It's not the 
only hazardous measurement, but is certainly one that requires an 
understanding of what can happen if you slip up.

Take care,
Bart



Tesla list wrote:
> ---------- Forwarded message ----------
> Date: Thu, 1 Nov 2007 03:04:59 +0100
> From: Kurt Schraner <k.schraner@xxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: mysterious coil failure / M and k Measurement (fwd)
>
> Hi Gary Lau,
>
> sorry for not having been clear enough! Of course you are right: when I 
> wrote "between the mains AC line and the rest of the circuit", I didn't mean 
> to remove the ballast. Of course, the ballast resistor should be adapted to 
> limit the current of the transformer in use. In my case, I had a transformer 
> with 12V/30A, and a current limiting resistor, limiting the current to 10A 
> or 15A. With the transformer in place, it's then feasible to move the 
> primary tap, without even switching off the supply. My coupling k 
> mesurements zipped Excels can be downloaded from:
>
> http://home.datacomm.ch/k.schraner/spreadsheets.htm
>
> Having verified the reliability of Paul Nicholson's ACMI and Mark 
> Rzeszotarski's M_and_k programs, nowadays I usually abstain from performing 
> the measurements, just relying on the calculations, which are within the 
> error limits of the measurements.
>
> Best regards, Kurt
>
> Tesla list wrote:
>   
>> ---------- Forwarded message ----------
>> Date: Wed, 31 Oct 2007 15:39:33 +0000
>> From: "Lau, Gary" <Gary.Lau@xxxxxx>
>> To: Tesla list <tesla@xxxxxxxxxx>
>> Subject: RE: mysterious coil failure / M and k Measurement (fwd)
>>
>> Hi Kurt:
>>
>> It's a worthy goal to modify this measurement technique to eliminate
>> the electrocution hazard.  But it's not clear to me that it's
>> possible to achieve this without the use of a resistive ballast such
>> as the hair dryer.  Placing a 6 volt transformer secondary across
>> most TC primary coils would be essentially a short circuit and exceed
>> the transformer's current rating.  Even if the transformer was driven
>> with a Variac, I would worry that there might still be some
>> non-linear behavior driving a near short-circuit, resulting in
>> non-sinusoidal waveforms and inaccurate measurements with common
>> DMM's.
>>
>> Or, are you proposing to still use a suitable (?) ballast on either
>> the primary or secondary side of the xfmr, and make sure that the
>> xfmr secondary current remains well below its rating?  What is the
>> minimum TC primary current that results in an induced TC secondary
>> voltage high enough to stay above the noise?
>>
>> Regards, Gary Lau
>> MA, USA
>>
>>     
>>> 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
>>>       
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