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

["Tesla list" <tesla@xxxxxxxxxx>]

---------- 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