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Re: Recycled: Measuring Coupling Coefficients
From: Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent: Sunday, November 30, 1997 8:59 AM
To: Tesla List
Subject: Re: Recycled: Measuring Coupling Coefficients
John,
Terry originally thought the same as you about the operating
frequency, but found that in fact the method is not dependent
on frequency. In fact, as the title of one of his posts pointed
out, this method is perhaps the best for most coilers as it does
not require very much in the way of test equipment, and yet yields
answers at least 1% accurate if you use a heating element or
high power resistor as the current limiting element (as opposed
to a light bulb, which is non-linear and introduces a bit of
error at 60 Hz).
Greg Leyh uses a variation on this method, where he applies 120
VAC directly to the SECONDARY and then measures the voltage at the
primary and the current at the powered secondary. It is always
useful to have information on several different ways to do things.
Then use the method that works best based on the equipment you
have at hand.
Always exercise caution when dealing with the 120 VAC power
lines!
Hope this helps.
Fr. Tom McGahee
----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-poodle.pupman-dot-com>
> Subject: Re: Recycled: Measuring Coupling Coefficients
> Date: Friday, November 28, 1997 6:05 PM
>
>
> From: John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
> Sent: Friday, November 28, 1997 12:46 AM
> To: Tesla List
> Subject: Re: Recycled: Measuring Coupling Coefficients
>
> At 01:11 AM 11/27/97 +0000, you wrote:
> >
> >From: Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
> >Sent: Wednesday, November 26, 1997 6:58 AM
> >To: Tesla List
> >Cc: terryf-at-verinet-dot-com
> >Subject: Recycled: Measuring Coupling Coefficients
> >
> >>
> >>
> >> From: terryf-at-verinet-dot-com[SMTP:terryf-at-verinet-dot-com]
> >> Sent: Tuesday, November 25, 1997 4:23 PM
> >> To: Tesla List
> >> Subject: Measuring Coupling Coefficients
> >>
> >> Hi All,
> >> I have been playing with measuring coupling coefficients lately.
I
> >> was just wondering if anyone has a relatively easy way to accurately
measure
> >> this elusive factor?
> >
> >
> ------------------------------------------------------ snip
>
> >Here's a recycled post that may be of some help to you
> >or maybe some other coiler who is seeking to determine K.
> >
> >Hope this help.
> >Fr. Tom McGahee
> >
> >From: Edward V. Phillips[SMTP:ed-at-alumni.caltech.edu]
> >Sent: Friday, August 08, 1997 2:50 PM
> >To: tesla-at-pupman-dot-com
> >Subject: Re: Mutual Inductance and Coupling Measurement
> >
> > Here is a pretty fundamental way to measure the mutual
> >inductance, provided you have a millivoltmeter. Feed a known
> >60 cycle current (say power line in series with 100 watt light
> >bulb) through one winding and measure the induced voltage
> >across the other. Suppose, for instance, that the mutual
> >inductance is 100 microhenries. This represents a reactance
> >of 0.0377 ohms at power line frequency, so the voltage will
> >be omega x M x I = 377 x 100 E-6 x 1 =37.7 millivolts.
> > Having measured M the coupling factor k is the
> >mutual inductance M divided by the square root of L1 x L2,
> >where L1 and L2 are the winding inductances.
> >Ed
>
> -----------------------------------------------------------------
>
> All -
>
> If you need a wiring diagram of how this test is made there is one in the
> Tesla Coil Design Manual. In this wiring diagram the components are chosen
> so that the millivolts are the uh of mutual inductance and no calcs are
> required. It is also safer because low voltage is used.
>
> Note, however, that this test is at 60 HZ and may be different at the
> operating frequency of Tesla coils.
>
> John Couture
>
>