Accidental Electromagnetic Fields?

@Mannyrock posted:

Hey Folks,

     For my AC power lines to all of my track sections, I run a set of 18 gauge wires from the power source to the track.  This light gauge wire is fine or me, because I run lots of lines.

   But, since I buy the black and red wires separately, I twist the wires around each other, in a spiral, to keep them together, before hooking them up..

   The thought occurred to me yesterday:

When a power wire is wound around in a long spiral run, doesn't this create an electromagnetic filed inside the spiral?  Yes, around the wire, no in 3D space because they cancel out.

So, doesn't the twisting together of the two wires create two electromagnetic fields? Yes, and they cancel each other out because current is flowing one direction in one wire, and back the other direction in the other wire- as a circuit pair.

   And, if so, do these fields affect (interfere with or reduce) the amount of amps that are getting to my track from my power lines? No way did you create enough inductance to change anything significant- let alone current reaching your track.

Highly suggest you watch a few videos on twisted wire pairs. https://www.youtube.com/watch?v=sB0INjc4Wl4

Another video https://www.youtube.com/watch?v=RVzM-b3okH0

Another video https://www.youtube.com/watch?v=nfSJ62mzKyY

The twist simply helps reject adjacent wires from cross talk.

@Mannyrock posted:

The thought occurred to me yesterday:  When a power wire is wound around in a long spiral run, doesn't this create an electromagnetic filed inside the spiral?   So, doesn't the twisting together of the two wires create two electromagnetic fields?

   And, if so, do these fields affect (interfere with or reduce) the amount of amps that are getting to my track from my power lines?

Well, first, each conductor has its own magnetic field, regardless of its proximity to other conductors. However, if the current flow is in the same direction as that of adjacent conductors at any given time (as with the windings on a motor armature), the magnetic fields reinforce each other, and increase the intensity of the magnetic field. Conversely, if the current flow is in opposite directions (as with the parallel conductors in paired wires, like lamp cord, or your twisted pairs), the fields tend to cancel each other out. I believe the twisting may increase this effect a bit, reducing the conductors' tendency to transmit (or receive) magnetic fields to and from adjacent conductors.

I've never really thought of it, but my assumption would be that reducing magnetic 'coupling' with nearby external conductors would also reduce any incidental transfer of power to those conductors, and thus result in smaller inductive power loss from your power feeds. I suspect the effect would be small, though, so I'm not sure it's worth worrying about, or that there's much you can do about it in any event!

@Mannyrock posted:

Hey Folks,

     For my AC power lines to all of my track sections, I run a set of 18 gauge wires from the power source to the track.  This light gauge wire is fine or me, because I run lots of lines.

   But, since I buy the black and red wires separately, I twist the wires around each other, in a spiral, to keep them together, before hooking them up..

   The thought occurred to me yesterday:  When a power wire is wound around in a long spiral run, doesn't this create an electromagnetic filed inside the spiral?   So, doesn't the twisting together of the two wires create two electromagnetic fields?

   And, if so, do these fields affect (interfere with or reduce) the amount of amps that are getting to my track from my power lines?

Thanks for any info.

Mannyrock

   

I like your curiosity and it highlights one of the many reasons model railroading is a great hobby. If you are interested, your question is a jumping off point for studying electromagnetic fields and waves, theory and applications. It’s a great path to understanding how a lot of the technology we use every day works. It’s a doorway into the satisfaction that comes with learning. In the age of the internet, the breadth and depth of this subject is more accessible than ever. Vernon demonstrates this with his links to YouTube videos. A good introductory book for the hobbyist might be best for putting it all in context, starting with the concept of a moving electric charge.

Any time electrons are flowing (electric current) there will be an electric field and a magnetic field. Its all coupled together. That’s the way God made the world. Any conducting medium can have characteristics of resistance, inductance, and capacitance. For DC current resistance is most important, but with AC current capacitance and inductance can become more important and might even dominate depending on the frequency. There is a whole field of engineering called electromagnetic compatibility/electromagnetic interference (EMI/EMC) devoted to understanding and managing these effects. Your posting asks about transfer of power through wires. I doubt you have anything to worry about there. If there is no electric load actually dissipating current (into heat) from your power source on the way to your locomotive, I doubt there are any issues. On the other hand, radio frequency interference can be a live topic in O gauge railroading. It leads to discussions on things like the merits of bus versus star power layouts for track. This is a topic that gets discussed a lot and you can read into it here on the forum.

Thanks for all of thMannyrockese excellent replies.

Normally we don't have problems with electromagnetic fields from Alternating Current (AC) 60Hz sources of any type (50 Hz in Europe), primarily because they are literally everywhere, i.e. all around us.  These fields come from all the wiring in our houses, the wiring between our houses and the power lines running through our yards and neighborhoods, from those lines, and all the way on up to from the massive transmission lines that connect power plants and major cities.

So, there's very little you can do on your pike to either increase or decrease these fields (at 50 or 60 cycles per second) that would interfere with anything using that power.  The system has already been made bulletproof, intentionally or by accident, over more than a hundred years of the world's general experience with AC power generation, transmission and usage.

You and your layout are immersed in it continuously.  You can easily detect this ubiquitous and omnipresent field by turning on your stereo, unplugging the far end of one of the audio cables coming into it from your turntable, receiver, tape machine, or SmartPhone, and touching the now-exposed center pin on that cable with your finger.   Assuming that your volume control is turned up high enough you'll hear a very recognizable low-pitched buzz as long as your finger (i.e. one kind of suitable antenna) is touching that pin.  The ubiquitous 60 Hz field is what you're hearing.

Going back now to general fields, if you instead pick another frequency, say 10,000 Hz, aka 10 KHz, (which is within the human audible hearing range), or 455 KHz (which is TMCC's Carrier Frequency between Base-x and Track), or 2.4 GHz (Computer WiFi), or any of 1000's of other special frequencies that are used by common devices around you, then you can cause a real problem, sometimes fairly easily.

When compared to those, you don't need to worry about 60 Hz.

Mike