Metglas cores

  • Last Post 19 August 2019
cd_sharp posted this 02 August 2019

Hi, everyone

While playing with a small Metglas core I had a big surprise to discover it is electrically conductive and more than that. Here is a picture:

I covered the core in insulating tape and wrapped about 20 turns on it, making sure to stay only on the insulated area. Then, I did a continuity test and a resistance test between one of the wire ends (red) and the core (black, in my hand).

What's going on here? Why the wire and the core are not electrically isolated?

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Chris posted this 02 August 2019

Hey CD,

If you mirror this experiment with a Capacitor, you will get the same result. Capacitive Coupling if memory serves is the cause.

All Transformer Cores and Coils suffer this problem. The Core ( Conductive Element ) is acting as a secondary, as a single turn, but capacitively coupled to the primary coil.


Perhaps the best one:

Ref: Minimising Capacitive Couplings and Distributing …


I believe we have covered this partly before, about Transformer shielding?

As long as there is no short, then you will be ok wink


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Vidura posted this 02 August 2019

Hey CD As your DMM is set to resistance it is DC, and not likely to have a capacitive effect, the Metglass cores have very sharp edges, which can cut the insulation while winding the wire. Use a fine sandpaper to smooth them before winding. Vidura.

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Chris posted this 02 August 2019

Hey Guys,

Yes true, Vidura is correct! I missed the DMM Setting sorry. 

Do look out for Capacitive Coupling though.

I use cut acrylic:


I hope this helps some embarassed


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patrick1 posted this 03 August 2019

hmm,  there is one thing....   impossible !! ;-D.  if it works with that core, surely it would, a block of iron.

i hope this is not throwing off our positive results, and giving false negatives.   i dout it. at this point ?

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patrick1 posted this 10 August 2019

okay i cant help but notice how terrible my photos are, - even @ 4k .  - so i dropped the file size down by about 95% with no less quality, woohoo for me.

anyways my cores are not playing ball. - im going back too mr preva -  but i managed too wind some 40gauge wire onto this tiny core, - 360ohms, and 120 owms, - but it isnt playing ball, - - parallel with my globes,  -  it was doing strange things, seemed too be backfeeding my PSU,  - but after i fixed that with a filter box and diodes. . - i cant seem too find any advantages, - its back too being a null transformer.  - havnt figured out why yet.  ... wish i could afford the air fares too this masonic lodge ;-D

anyways the work dosnt end, - clubbing is not for me these days. -   let the electrons flow

ferrite salvage

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Chris posted this 10 August 2019

Hey Patrick,

I have used Ferrite and had a lot of success. Graham Gunderson used Ferrite with a COP >= 5.0.

Smaller Cores = less Flux Density. However I have used the same core size and seen results.

Metglass Cores are excellent, but also harder to work with.


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patrick1 posted this 12 August 2019

Thats cool, i have learnt a few things in 24 hours, - going well. ;=0

i have solved the problem of my power supply blowing up. which it did.  ...  blew a hole in the 1500v (noshootthrough rated) transistor. ,,,  anyways my new filterbox has removed that fault. - however ,i suspect there is some TANK circuit magic in that fault... -  anyhoo COP 2 from my 360ohm / 120 ohm coils....    and lots more experiments for today.  ... also im about too order a lot of these...   are you interested in going halfs anyone ?

only 2 left, so il order tonight, and can split it before shipping if your keen.

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  • Vidura
Vidura posted this 12 August 2019

Hey All!
There is a possibility that I can get the AMCC170 core that i bought , and didn't arrive at time. Fir the moment I made some experiment with ferrites, as i was short on cores of a considerable mass I stacked 18 E core segments to a block of 30 x 30 x90mm, and made some custom coil formers. I got very nice sawtooth waveforms and opposing currents in some configs, but then i tried a 3coil POC setup and grounded the centertap of POC on the connector of my power supply. A very strong oscillation with high voltage occurred and damaged the current meter of the power supply, although i had connected a common mode choke on the output. I had similar results with such a configuration before, very high voltage and high frequency on the centertap, around 4000v @ 100khz, in first moment i touched a wire and get a pretty strong shock. then I made some attempts to pump current with this setup, I'll post a video soon from the tests and some more info. The Power supply still works luckily, but the current meter is resting now at 70mA all the timesurprised. I will replace with analougos meters I think, as even with a quite good RF filter the interference passes thru on higher power levels.

Regards VIDURA.


Chris posted this 13 August 2019

Hey Vidura,

I hope your cores come soon!

Wow, yes please be careful. It is easy for a large Current to come back and damage equipment. I hope you can fix it!


patrick1 posted this 17 August 2019

those e cores i pasted 2 messages above here. - are going too arrive in a few days, - apparently they are good for 100khz

please people pm me a link of a test i should perform with them

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leonel posted this 19 August 2019

Hey cd_sharp  and @ Cyril Smith has written about it, check it, is very interesting!

Creating Electron Current in Ferromagnetic Wires by Moving Magnetic
©Cyril Smith, April 2015


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