Information on Magnetic flux within a Toroid.

Hello,

Use the same formulas you would use for other core shapes except that now you need not worry about an air gap at the joints. Everything else remains the same.

The H field at any point inside the toroid is the number of ampere-turns (NxI) divided by the magnetic path length L (H=NI/L). Calculate the magnetic flux B using B=uH, where u is the magnetic permeability of the toroid core.

Most torid manufaturers have a web site with fairly detailed instructions on calculating this. The magnetic materials used in toroid are non linear and the calculation of flux is dependant on the exact core chosen, the number of turns and current as listed above but also the frequency of operation and about a bazillion other factors.

I have used and recommend an electromagnetic modeling program called FEMM. It has the equations built in and produces a very large quantity of useful data in a short period of time.

It was freeware last I looked.

http ://www.femm.foster-miller.net

The accuracy of the results will mostly depend on the accuracy of your inputs. So, be very careful in entering information or use the standard material libraries whenever possible.

Best wishes,

Mr. Gee

(It will only do two dimensional slices of a complex solid like a torroid last I checked but that limitation should be little matter for most projects. If you need better go with 3d solid modelling and professional grade FEA software, but, expect to pay for it.)