BV08 transformer capacitance, comparable to mic cable capacitance?

[Moby]

Thank you, Moby. I think you'd be doing us all a favor by making the measurement and posting it here.

U welcome, but I still gon't get what I have to measure. Attaching Bv.08's primary to LRC meter will probably give missinformation value. Of course, I can measure it if author really wants that info.

 

[abbey road d enfer]

U welcome, but I still gon't get what I have to measure. Attaching Bv.08's primary to LRC meter will probably give missinformation value. Of course, I can measure it if author really wants that info.

I would think that measuring the impedance over a wide frequency range would give two asymptotes and one resonance. The first asymptote would be constant, representing teh DC resistance, teh second asymptote would represent the effects of teh parasitic parallel capacitance in series with the DCR, and the peak frequency would allow calculating the inductance. Of course the effects of the parasitic parallel (loss) resistance and the parasitic impedance of the test equipment would still mess with the measurements, but it would give a set of good ballpark figures.
The parallel parasitic capacitance is what te OP wanted to know, from what I gathered.
It does not change my opinion that his question was not pertinent since the major cause for HF loss is the leakage inductance.

 

[Moby]

I would think that measuring the impedance over a wide frequency range would give two asymptotes and one resonance. The first asymptote would be constant, representing teh DC resistance, teh second asymptote would represent the effects of teh parasitic parallel capacitance in series with the DCR, and the peak frequency would allow calculating the inductance. Of course the effects of the parasitic parallel (loss) resistance and the parasitic impedance of the test equipment would still mess with the measurements, but it would give a set of good ballpark figures.
The parallel parasitic capacitance is what te OP wanted to know, from what I gathered.
It does not change my opinion that his question was not pertinent since the major cause for HF loss is the leakage inductance.

I understand what you talk about but question was about the primary capacitance, not impedance. So, yes, it's measurable but was it really the question. Btw, when we talk about the inductance of the Bv.08, it really depends from the choosen frequency since mumetal's core has nonlinear AL.

 

[abbey road d enfer]

I understand what you talk about but question was about the primary capacitance, not impedance

Measuring impedance is the way to measure inductance. It's an indirect method.

. So, yes, it's measurable but was it really the question.

Yes. The description of what he wanted to assess made it clear enough.

Btw, when we talk about the inductance of the Bv.08, it really depends from the choosen frequency since mumetal's core has nonlinear AL.

Of course, but in conjunction with the estimated capacitance, it will give the inductance value at the resonance frequency.
A complete set of measurements would include putting capacitors in parallels, for various resonant frequency, which would allow calculating the inductance at those frequencies.
Actually, it's not a very interesting parameter, except at VLF.

 

[Moby]

OK, whatever the question is, I measured the primary capacitance. Primary in series, secondary in series, not terminated. As I presumed it's not linear. It starts to be measurable at approx 4Khz. Also, termination of the secondary winding makes a big changes but the question was about the primary capacitance. I hope this will help. Not sure for what but I did my homework
@4Khz=1.1pf
@8Khz=16pf
@10Khz=19pf
@20Khz=23pf
@40Khz=25pf
@100Khz=28pf

Cheers!

 

[abbey road d enfer]

That is weird. Capacitance shouldn't change that much with frequency or loading.
Can you describe/draw you test fixture?

 

[Moby]

That is weird. Capacitance shouldn't change that much with frequency or loading.
Can you describe/draw you test fixture?

I explained. Non terminated primary attached to the LRC meter, open secondary.

 

[abbey road d enfer]

I explained.

No you didn't. It's only now that I find you're using a RLC meter. There are other methods for measuring reactive components

Non terminated primary attached to the LRC meter, open secondary.

The fact that the apparent capacitance changes with frequency shows that the LCR meter cannot discriminate betwwen the sum of reactive components (L and C) and C alone.
What's your RLC meter? Does it have the capacity of switching between parallel and series mode?

 

[Moby]

No you didn't. It's only now that I find you're using a RLC meter. There are other methods for measuring reactive components

The fact that the apparent capacitance changes with frequency shows that the LCR meter cannot discriminate betwwen the sum of reactive components (L and C) and C alone.
What's your RLC meter? Does it have the capacity of switching between parallel and series mode?

Yes it has. In both modes, parallel or series capacitance value is changing with the frequency
I have several RLC units but this time I used the desktop Ruoshui 4090c.

 

[abbey road d enfer]

OK. I see it is not capable of discriminating the inductive and capacitive parts. It takes the global reactive value and assumes it's only a capacitance or an inductance. That's why the apparent capacitance varies with frequency. A good evaluation of such a small capacitance requires a much higher test fequency for asymptotical analysis. Then the parasitic capacitance of the test equipment becomes an issue.
From your measurements, we can assume the exact capacitance is a little over 30pF. A good enough figure for the purpose the OP considered. Since it is a parasitic value, perfectly accurate measurement is useless, since it is susceptible to vary significantly from sample to sample.
Thanks for your efforts anyway.

 

[terry setter]

I agree. Thank you, Moby. Clearly you invested some siginificant time and energy It seems this particular issue has now been put to rest - and may it rest in peace.