# High power, short distance electrical transmission problem

1. Jan 23, 2010

### taylaron

I’m in a situation where I need to power 150 machines, each one consuming 2kW of power. The trick is that it rolls on a metal track at high velocities. I am concerned about transmission loss and type of contact.

I could power the machine with a physical contact via carbon bushings to a track which has conductors mounted on it. This is the most simple and traditional way to solve this problem. The downside is that the bushings wear out and the polished surface is filthy. My solution needs to be low maintenance. Bushings may be the best option to power my machine; but consider the following idea.

(I'm not an electrical engineer yet, so I don't have a solid education on the following areas.)

I'm aware that by using resonate inductive coupling, one can set up a primary (source) and secondary (target) coil of wire; here the primary has high frequency electricity running through it, and the other resonates at that frequency, inducing current in the secondary coil and viola, wireless electricity. This is a basic explanation. The downside for my application is that I would have to place countless coils of wire on the surface of the track. I’m not sure this would work because there would be fluctuations in the field strength as the machine rolls along the track. The necessary wire would also be expensive. My solution also needs to be relatively affordable. Pretty sure this is not practical for my application.

Another method which I don't fully understand is one that uses RF waves to transmit power. To my understanding, an antenna emits RF waves and some of that energy is inherently absorbed by the environment. Unfortunately, power is lost even when no electronics are on (next to ohmic heating.) Field strength diminishes with the square root of the distance from the source. Correct? The upside here is that the range on my application is near zero. Current applications are limited to devices like cell phones… But I need 2kW of power... big problem. Is using RF waves possible without frying everything that lives?
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Another requirement is that the field emitted needs to be short range. I cannot have foreign electronics nearby sucking energy from my power system. The track will be elevated to about 20ft off the ground, about the height of a two story house. This application would be placed in well populated areas.
What is my best option?

-Taylaron

Last edited: Jan 23, 2010
2. Jan 23, 2010

### vk6kro

Your application is similar to the case of electric trains.

They find the best approach is to use a mechanical contact to a third rail or an overhead wire but at a high voltage to keep the current down.

RF and inductive power transfer work best when very small coupling distances are needed.