formula for air cored inductors

[paul ewart]

Can anyone help,. i'm looking for the formula (mathematical) or otherwise, which will allow me to design the work coil of a small induction heating unit.
Power output =around 500w

Frequency = around 50KHz


The main problem, here is - how many turns, at what pitch gives how many micro henries

 

[zachtheterrible]

There are three things that affect the value of an air coil:
1. # of turns
2. Diameter
3. Length of coil

Search on google for: air coil inductance calculator. There's a ton of calculators out there.

Or if you want, you can do the forumla . . . which i dont remember :roll: someon else will

 

[panic mode]

i tried to paste the topic name "formula for air cored inductors" and there was plenty of hits...

 

[Russlk]

I have used this formula:

Inductance in microhenries = n^2(r^2/(9*r + 10*L))
Where n = number of turns
r = radius = 1/2 diameter of coil
L = length of coil
It does not matter whether you use metric or english units.

 

[paul ewart]

Hi Russlk,
Brilliant!!!! very many thanks,the formula is exactly what I was looking for. At least I can now make an intellegent estimate as to the topology of the coil and hence it's value. ------ You're a STAR.

 

[paul ewart]

Thank's for the idea Panic Mode, I gave it a shot, but only got bogged down in loads of irrelevent applications. --- but, a good idea nontheless!! :wink: