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Mags,
Here is the response from ChatGPT on this subject only I used a round coil instead of a triangular one.
You said:
I have a round 30 turn coil that is 5" in diameter. I put a 1" pair of ferrite cores over the coil and insert a single turn. I now apply a 30 volt pulse to the 30 turn coil and I will measure what amount of voltage across the single turn?
ChatGPT said:
If the coupling is reasonably good, you can treat this exactly like a transformer.
Basic transformer relationship
Vs=Vp×NsNp
Vs=Vp×NpNs
Where:
Vp=30Vp=30 volts (your applied pulse)
Np=30Np=30 turns
Ns=1Ns=1 turn
Ideal case
Vs=30×130=1 volt
Vs=30×301=1 volt
Realistic case
The actual voltage depends on coupling coefficient kk, which in your geometry may be significantly less than 1, especially because:
The ferrite cores are only 1" while the coil is 5" diameter → not fully linking the field
The single-turn loop may not tightly couple to all flux
Pulse rise time matters (leakage inductance)
In practice:
Vs≈k×1 V
Vs≈k×1 V
Typical kk for such a poorly-fitting geometry might be 0.1 to 0.5, so the observed voltage could be something like:
0.1–1.0 volt
If the single turn is placed entirely inside the closed ferrite core
…and the 30-turn coil’s flux fully passes through that core, then kk could approach 1, and you would indeed see very close to 1 volt.
If you want, tell me how the ferrite cores are arranged over the coil (e.g., clamshell? does it close fully around the conductor?) and I can estimate a more accurate coupling coefficient and real output voltage.
You said:
OK, now if I place an additional ferrite core set on the same 30 turn coil, how will this affect the single turn measurement on the first ferrite core?
ChatGPT said:
Short answer: The voltage on the first single-turn will stay almost the same, unless the second ferrite core significantly diverts flux away from the first one.
But let’s explain why.
✔ What happens when you add a second ferrite core set to the same 30-turn coil?
You now have something like this:
One 30-turn primary coil
Two separate ferrite cores placed around different parts of the coil
Each core may contain its own secondary winding (your single turn)
This behaves like a transformer with multiple secondaries, except that the magnetic paths are not shared—they are local to each ferrite core.
Key Principle
The voltage induced in a secondary is proportional to the local magnetic flux through that core:
Vs=NsdΦdt
Vs=NsdtdΦ
Adding another ferrite core simply creates another local flux path, but it does not steal flux from the first core unless the coil’s field is “flux-limited.”
✔ What actually changes?
Case 1 — The ferrite cores are far enough apart and not interacting
Each core sees roughly the same field generated by the 30-turn coil.
The first core still sees nearly the same flux as before
The induced voltage in the first single-turn stays the same
The second core also produces its own induced voltage (also ~1 V ideal)
This is the most common situation.
Case 2 — The cores are very close together so that their flux paths compete
This is uncommon but possible if:
They are touching or nearly touching
Their magnetic circuits strongly interact
The ferrite partially saturates (unlikely with 30 V pulse unless pulse is long)
In this case, the effective permeance of the system changes, and the flux divides between the cores. However, even then:
The first core might see slightly less flux
The reduction is usually small unless the ferrite saturates
✔ Practical conclusion
Adding a second ferrite core will NOT significantly change the induced voltage in the first single turn.
You will still measure approximately:
Vs1≈3030=1 V×k1
Vs1≈3030=1 V×k1
where k1k1 is the coupling coefficient to the first core.
The second ferrite core will produce:
Vs2≈1 V×k2
Vs2≈1 V×k2
Both voltages exist independently.
✔ Exception: If your pulse is long and the ferrite saturates
Then inductance drops, current rises, flux changes, and both secondary voltages may fall as the ferrite saturates.
If you tell me:
Pulse duration
Pulse rise time
Ferrite material type (e.g., 3C90, N87, etc.)
Coil current
Placement of cores
…I can calculate whether saturation is possible and estimate the exact performance.
So, we seemingly have a dilemma!
Pm
Edit: Actually there is no dilemma as each added core reduces the triangular coil's current and thus the flux which in turn reduces the E-Field in each added core section.
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Topic: Transformer Induction (Read 26471 times)
