Dear Roland,

if I understnad your question correctly, this is a matter of economics.

Transferring power comes with losses and losses grow by I²*R.

The length of the conductor is less important, if you can vary the input dimensions.

Example assuming DC-current:

A line of several kilometers in length has a resistance R.

If you transfer a megawatt, driven by 1000V, current is 1000A, losses are (1000A)²*R.

The same power can be transferred using 1 Million Volts and 1A only reducing the losses dramatically but now demands high-voltage DC transmission.

Today, systems are in development to work on +/- 1 million volts and transferring energy can be done economically across distances exceeding 1000km.

Cheers - Martin

If you mean by inductive coupling, there is no limit, but for a loop a long way from the driving loop, the driving magnetic field will need to have a very large volume so require a lot of stored energy so high currents in the driving coil, which have high losses. Also, the magnetic fields will drive currents in any other conductors nearby, so losing power. You will need to calculate the efficiency for any particular application.

For 100A power transmission you'd need 1 AWG wire. That has a diameter of 7.34822mm, and a resistance of 0.406392Ω per km. So over a 1km distance you'd lose 0.406392 * 100 = 40.64V

I guess your question could be clarified. When I read it I understand a question related to the insulation distance between two conductor which will depend from the dielectric and frequency.

In summary you got many different answers for the same question.

Theoretically, there is no maximum distance limit; however, the magnetic field decays to levels at which the mutual induction or coupling becomes very small to be considered. The corresponding value depends on quantities such as the value of the current flow. Therefore, there is no a specific general maximum distance.

The most probable understanding of the question is what is the spacing between phases in a powerline to allow mutual induction or magnetic effect. This depends on voltage and current levels, which is a reflection of strength of the magnetic field and therefore determines the point of Corona effect phenomenon. Thus, maximum distance to allow conduction to another conductot depends on voltage and current levels as interelated in the electric field and inductance equations.

There is no limit. Induction occurs due to magnetic flux. A conductor carrying current generates a magnetic field and a conductor moving within a magnetic field generates a current. In AC currents, the magnetic field is constantly moving, so it can induce current in a conductor that's not moving.

Radio transmissions are magnetic waves. The waves are captured by all conductors in their path. We know that radio waves can be sent over billions of miles. The Voyager spacecraft's 22W signal was detected by radio telescopes in 2013. At that time, it was over 11 billion miles from earth!

So, the question is, how strong do you want the induced current to be over what distance? All of this can be predicted using Faraday's Law.

Induction is not the same as radiation. Both are described by the Biot-Savart equations.

With induction, if there is no load present, no energy is lost from the coil. With radiation, the energy is lost whether there is a load present or not.

The radiated field falls off as 1/r, which means that the power travelling outwards is constant at any r. The inductive field falls off faster than this so the power can't be travelling out (unless a load is present, and that modifies the fields locally so that power flows).

You can not transfer either voltage or current from one guide to another - this term has no physical sense. I think that you mean the wireless transfer of electrical energy and you are interested in the practical range of this phenomenon - is it?

There is no simple answer to your question - if this is indeed your question. Effective energy transfer starts at a fraction of a millimeter, it can also reach hundreds of kilometers if we switch to the microwave range and make the appropriate transmitting and receiving antenna (made of course from the conductors). In practice, it is possible to reach a range of several meters without using excessively complicated or expensive solutions. Here is an interesting achievement described:

https://www.disneyresearch.com/publication/quasistatic-cavity-resonance-for-ubiquitous-wireless-power-transfer/

It will depends of lots of parameters as the amplitude of current and voltage, wich conductors, comditions of the air..

For clarification of my question, the current and voltage are present in my applicator where the materials being heated. Then voltage and current from the generator will be induced or transfer to the RF applicator shielding surrounding the heating system. My question is what is the maximum distance both voltage and current can be transferred. I think, this question was already answered in my different questions I posted. Thanks everyone for sharing your knowledge.

There is an interesting but not widely known application of such a configuration:

Basically all conductors which are close to each other form a directional coupler (if electric AND magnetic coupling is involved otherwsie there is no directionality)This is also valid at dimensions much smaller than lamda/4 but we assume to stay in the near field (no radiation).The application is to extract a few hundred Watt from a high power line via the ground conductor(ususally on top in rural areas of third world countries...These days its probably easier using photovoltaics

Hi Rolad,

The disruptive electric field is equal to 3 million volts per m.

However, when the air is wet, or in the presence of metal tip, it is much less. Remember the lightning ...