planar coil magnetic field strength calculation

[volker@muehlhaus]

Ok, let's use 1MHz for calculation. You then have a skin depth of 65µm.

Cross section at 10mm wire diameter is 10mm*pi*0.065mm = 2 mm²
To avoid overheating of the conductor, a rule of thumb is to limit current in copper conductors in air to 6 A/mm²

 

[Salvador12]

its not so much about current limit, I could technically use the wire geometry and size best suited and have water cooling if it is a pipe like wire etc. I think the biggest problem here is to achieve reasonable magnetic field strengths because if the inductance will get high there wont be any device strong enough to drive enough current to the coil to get it to melt yet to get it to the necessary b field strength.
this is what worries me.
Ideally I could use the generator itself to drive its own field coil but my output is low voltage high amperage, so in theory I can get kiloamps of current but only if the resistance or inductance is very very low.

 

[volker@muehlhaus]

But it's all related ... you are trying to cheat and ignore losses, but real wire has real losses. That's why others need superconductors for this field strength.

If you want to build an oscillator, you need high Q factor (=low losses) to have high current in the tank circuit. It's all about losses.

 

[Salvador12]

I know otherwise with low Q I would either have to supply large amounts of energy to the oscillator or the self oscillation would die,
ok but for a start can I get any decent field strength with a coil that has an inductance near 1 ohm? My load is also about 1 ohm and ideally I could have equal resistances in the two parts its just that the load itself is almost entirely a resistor so has very little (ppm maybe) inductance but the field coil would be more inductive than resistive so maybe paralleling multiple smaller coils make the deal?

 

[mtwieg]

I can say for certain that a 1T field can't be made without cryogens or lots of water cooling. And that's at DC (with an air coil), 1MHz is basically nonsense. If you were to create such an AC field you'd probably experience peripheral nerve stimulation just by being near it. And probably burn yourself from the inside out.

Creating 1T for short periods at a low duty (like <10%) is somewhat feasible, but still not easy.

And this is basically regardless of the size/shape of the coil.