Thane Heins Perepiteia.

[Groundloop]

I'm afraid this won't work because the bemf flux from the center secondary has no other way to go than into the primary.

Where can I find large (min. 4") ferrite or better toroids?
mmm, metglass comes to mind (with a soft-iron center bar)

What if I use an air core coil in the center as a primary, will that work?

@Mr.Entropy,

OK. Will try that also..

Groundloop.

[johnnyl]

Luc (and Thane!):

Thanks so much for the information!  I'm digging in trying to understand it on a deeper level.  Looking forward to learning more...

Thanks,

Johnny

[M@rcel]

Do I understand this correctly? An airgap in the center primary is ok as long as
- the secondaries have lots of windings and/or
- the outer toroid has the lowest reluctance possible

Mark the "and/or", for testing the "or" might be usefull

[Groundloop]

Do I understand this correctly? An airgap in the center primary is ok as long as
- the secondaries have lots of windings and/or
- the outer toroid has the lowest reluctance possible

Mark the "and/or", for testing the "or" might be usefull

Magnetic reluctance or "magnetic resistance", is analogous to resistance in an electrical circuit (although it does not dissipate magnetic energy). In likeness to the way an electric field causes an electric current to follow the path of least resistance, a magnetic field causes magnetic flux to follow the path of least magnetic reluctance. It is a scalar, extensive quantity, akin to electrical resistance. Magnetic flux always forms a closed loop, as described by Maxwell's equations, but the path of the loop depends on the reluctance of the surrounding materials. It is concentrated around the path of least reluctance. Air and vacuum have high reluctance, while easily magnetized materials such as soft iron have low reluctance. Air gaps can be created in the cores of certain transformers to reduce the effects of saturation. This increases the reluctance of the magnetic circuit, and enables it to store more energy before core saturation.

What we want is a primary with a higher reluctance than the secondary. There is many ways to do that. One is by choice of material used in the cores. One is by using air gap in the primary. One is by the number of turns in the coils. etc.

Groundloop.

[M@rcel]

Thanks for the info, clears things up. One question: Why is the reluctance dependant on the number of turns?