# ElectroMagnetic Field

rashidahwazia
Hi all,

I am designing vending machine to be used outdoors in a train station.
I am a mechanical engineer and i don't know much about electromagnetic fields.
The fact is based on what I have read, in train stations in which the train is working with electric power, the power lines are high voltage and low frequency. and high voltage (probably generating high current) with low frequency will make a powerful electromagnetic field.

1. is it true?
2. if it is true, what effect does this powerful electromagnetic have? (i've read that one of the effects is that it affects or damages electrical boards and components inside other machines, but i also don't know whether its true or not)
3. if it affects electrical components in my machine, how can i prevent it? should i use a specific material like stainless steel over mild steel or other materials? if so, does the thickness of the body matter?

Homework Helper
You can probably find some information by searching on that topic.

High voltage is used to keep the currents low.
With straight wires and relatively low currents the magnetic fields are not likely to be that strong.
Chances are that the random child with a permanent magnet toy will be more of a problem.
However, I don't know the exact answer to this question.

rashidahwazia
Dear Notime,

""High voltage is used to keep the currents low."" ? it will highly depend on the load i believe, isn't it?

and Also I am not sure why but the electromagnetic filed is really considerable in train stations with electric power as the main source.

EMP should be Electromagnetic pulse, right? is it the same as electromagnetic field? or is it a part of it? or? I am not familiar with this area at all.

Homework Helper
Well P=EI.
Since the load is concerned with power then increasing voltage decreases current required for the same power.
Current in a conductor detemines the magnetic field.

I am sure magnetic fields are measurable in a train station.
Perhaps more so from the train motors.
But unlike the child's toy magnet I have never seen metal objects move around because a train started up. So the child hitting your machine with their toy will probably induce greater current that the train will.

If you have very sensitive circuits then either train or magnet could be a problem.
EMP is, as you say, Electromagnetic pulse.
This study area considers the effects of currents induced in your equipment by magnetic fields.

Eidos
If you wish to protect your circuits, you can simply enclose it in an electrically conductive material. This is the principle behind the Faraday cage.