Do transformer radiations effect things?

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Plexified
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Do transformer radiations effect things?

Post by Plexified »

Do transformers radiate, if so , do they effect things? And if they are mounted on steel , copper , or aluminum does it matter? What is the pattern of this radiation , if it does exist. Assuming we run an I E core. Does a core matter. What about a donut core ? Torroid ? Power or Output ? Have you thought about this ? I wonder if you have , I have .... And do you think of winding your own iron .... Do you use Grain oriented steel or no. HMmmmm...
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Re: Do transformer radiations effect things?

Post by tubeswell »

AC will get induced into any inductor within sufficient range of an AC source. Wire can be an inductor. A transformer is a device that works by electromagnetic induction.
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Re: Do transformer radiations effect things?

Post by xtian »

Yes. This is why I use the "headphone trick" to listen to the position of the PT wrt the OT before committing to placement.

I understand toroidal PTs don't radiate? But haven't built with one yet.
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Re: Do transformer radiations effect things?

Post by pompeiisneaks »

xtian that is also my understanding of the torrodial, they cost more due to being a bit more of a PITA to build compared to the older style, but have no hum issues and are used often in HIFI due to being so much better for audio work.

I definitely need to try building with one at some point.

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Re: Do transformer radiations effect things?

Post by JazzGuitarGimp »

If I'm not mistaken, I think toroids do indeed have a narrow sliver, wedge shaped EMI emission zone that emirates from the point where the winding starts. The good news though, is since the transformer pivots about its center mounting bolt, the emission is easily "aimed" in a non-offensive direction.
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Re: Do transformer radiations effect things?

Post by R.G. »

Plexified wrote: Tue Jun 13, 2017 5:46 am Do transformers radiate, if so , do they effect things?
Yes, they do. A generated magnetic field of any kind radiates through free space, declining in intensity by the square of the distance change. So if you double the distance from a magnetic disturbance, the intensity goes down by a factor of four.

Ferromagnetic materials are better "conductors" of magnetic fields than free space. So they will tend to suck in whatever magnetic fields exist around them ( this goes with a whole lot of caveats and special cases, but it's a good way to think of it). A magnetic field would "prefer" to be inside iron (or nickel, cobalt, a few others and some alloys of them) by a factor of 3000 to about 20,000.

The down side to this is that any time there is an air gap where the iron is not a complete circular path for the magnetic field, the field REALLY doesn't want to go straight across the gap, and so it fringes out around any air gap in the iron. The longer the air gap, the worse the fringing. So in an E-I core setup, the M-field tries to escape the iron at the junctions of each E and I. Those are the big radiating parts of an E-I core.

A conductor does some fencing in of magnetic fields. M-fields trying to cut through a conductor generate an electrical eddy current that opposes the M-field getting through. Superconductors are perfect shields for M-fields, as they perfectly oppose the field cutting through. Real conductors like copper are less effective. This is the origin of the copper "belly band" on E-I transformers. It forces some of the leaky M-field back into the iron. Transformers with belly bands emit less M-field leakage than ones without them.
And if they are mounted on steel , copper , or aluminum does it matter?

Yes, it does. But in complex ways. Seems like I typed up a polemic on this topic recently. Maybe on the "copper chassis" thread. It's not easy to say steel, copper, or aluminum is better than the other without taking into account the exact physical setup and measurements.
What is the pattern of this radiation , if it does exist. Assuming we run an I E core.

Fringes bulge out, barrel-shaped-ish around every place the Es and I's touch, where there is air between them. This emission diminshes by the inverse square too. Distance is the cheapest form of shielding. :shock:
Does a core matter.

Yes. In fact, things like how tightly you joggle and push the Es and Is together to eliminate air gaps matter. And in fact the iron history matters, as you see a change in magnetic properties if the iron has been hardened by mechanical stresses. Whether the bolts that hold the Es and Is together are tight, and whether they are insulated from the iron so they don't form a shorting loop that includes part of the iron and pushes the M-field into higher densities near the corners matters.

One of the common myths is that cardboard bobbins matter. They don't. Any non-conductive, non-magnetic material is OK for a bobbin at M-field strengths you can achieve inside iron.
What about a donut core ? Torroid ?

Toroidal/donut cores are much more magnetically efficient than E-Is because there is nearly no air gap. So the M-field can stay almost entirely in the iron. So M-field emissions are much smaller to start with. In addition, toroids can be about 1/3 the size and weight of E-Is because of some ramifications of the M-field efficiency. But they have certain other ways they're fragile. Still, not nearly as much emitted M-field.
Power or Output ?
Same thoughts go into the design of both. There are different amounts of leakage from the coils put over the cores, but toroids have always been a more efficient, if slightly more fragile and difficult to work with as well as much more expensive alternative. For OTs, there are other quirks in frequency response.
Have you thought about this ? I wonder if you have , I have ....
Yep. I made my living designing magnetics for a Major Computer Company for several years. Thought about it a lot.
And do you think of winding your own iron ....
I have in the past, yes. My best advice is - don't do that. It's a huge amount of work, and although the materials are cheap in huge quantity, they're quite difficult to get for average people. And it's labor intensive. Do this only if you are prepared to pour lots of time and money into it just because you like the fiddling with it, something like model railroading, or restoring classic cars.
Do you use Grain oriented steel or no.
I did, yes. It's even less worth the effort if you don't use GOSS.
JazzGuitarGimp wrote: Tue Jun 13, 2017 5:17 pm If I'm not mistaken, I think toroids do indeed have a narrow sliver, wedge shaped EMI emission zone that emirates from the point where the winding starts. The good news though, is since the transformer pivots about its center mounting bolt, the emission is easily "aimed" in a non-offensive direction.
This is one of the quirks I was mentioning. It can be greatly reduced by overlapping the windings or making a "perfect" wire exit so the end of the last turn takes off just at the start of the first turn, or by putting on a diameter shield, or several other techniques. In wound iron-strip cores, the outer and inner ends of the iron strip radiate too, but this is somewhat shielded by the overlapped windings.
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