Where do you people buy electronic parts in USA?

[ZipZapOuch]

If I could buy a 100uh toroid inductor 30a that will be better than winding my own.

Small, toroidal inductors can be wrapped very crudely and still perform surprisingly well. Just make sure to use magnet wire when you wind. I would recommend a bobbin to hold the toroid when you mount it on the PCB and use a foam adhesive to suppress any physical vibrations that can develop from magnetostriction when pushing at core with high magnetic fluxes.

Magnetostriction, a Source of Noise in Transformers - Simcenter

Reducing the noise due to magnetostriction is no easy task. It requires a deep understanding of the forces acting on and in the core laminations that only electromagnetic field simulations can provide.

blogs.sw.siemens.com

 

[tepalia02]

Sparkfun electronics is a dependable source.

 

[gary350]

 

[ZipZapOuch]

Look at the formula for magnetic field strength (H).

H = I * n / L

L is length of the coil,
n is number of turns an I is current.

Of course the winding on one small area of an inductor will yield higher inductance. Money could have been saved by using a smaller core if you only want to wind a small arc of the larger core. The way a toroid is wound depends on the core material & size of toroid you can get for a target price, inductance you need, the winding equipment you have and the wire gauge you can work with.

 

[Tony Stewart]

Is there a place to read and learn about toroid's.? I need 2 toroids for 1200 watts and 80KHz.

https://www.pes-publications.ee.ethz.ch/uploads/tx_ethpublications/15_ThreePhase_Common_mode.pdf

 

[Tony Stewart]

if V=245, load = 50 ohms = XL(f) f= 80 kHz, L = 100uH Pd = 1200W

https://www.pulseelectronics.com/round-wire-coil-cmc/

Get Coil designs here

Consider 3 Phase.

Define parameters of everything 1st.

Coils are not rated in kW ,rather in losses at saturation threshold with EC losses.

Product Finder – Pulse Electronics

productfinder.pulseelectronics.com

I'm assuming this is for induction heating of steel.

Specify for maximum efficiency or MPT then design accordingly.

Power inductors are usually low L like 1 uH > 100A due to limits on L/DCR ratio with size.

 

[gary350]

4 inductors from Australia. Time to test them with my meter. 5 inductions in series works better than before. Nothing is over heating.

 

[ZipZapOuch]

4 inductors from Australia. Time to test them with my meter. 5 inductions in series works better than before. Nothing is over heating.

View attachment 144442



View attachment 144441

Since they are from Australia, I guess they are wound the other way around.

 

[gary350]

What is the best way to mount inductor toroids so the magnetic fields do not interfere with each other?

 

[ZipZapOuch]

What is the best way to mount inductors so the magnetic fields do not interfere with each other?

If they are toroids, there is no external magnetic field so, in theory, it doesn't matter.

 

[Tony Stewart]

If they are toroids, there is no external magnetic field so, in theory, it doesn't matter.

Coupling will be maximum when parallel < OD range

 

[gary350]

Coupling will be maximum when parallel < OD range

But the value will be 20 uh in parallel.

 

[Nigel Goodwin]

But the value will be 20 uh.

You misunderstood what he said - he never suggested putting them electrically in parallel.

 

[ZipZapOuch]

Coupling will be maximum when parallel < OD range

What?

There is no external magnetic field around a toroid inductor. That is the key benefit of taking the time, effort and odd equipment to wind wires through the hole of a donut. Known as total magnetic field confinement.

Toroidal inductors and transformers - Wikipedia

en.m.wikipedia.org

And mathematical proof here...

 

[gary350]

What?

There is no external magnetic field around a toroid inductor. That is the key benefit of taking the time, effort and odd equipment to wind wires through the hole of a donut. Known as total magnetic field confinement.

Toroidal inductors and transformers - Wikipedia

en.m.wikipedia.org

And mathematical proof here...

This is good to know. I graduated 1970 from 2 year electronic school they did not teach about Toroids. I don't think I know about toroids until about 25 years ago. I learned a lot in the past 2 weeks about toroids reading and watching videos and experimenting with them. .

 

[Tony Stewart]

Yes very little B field escapes the torroid, but to say there is none is false.

3-D Vector Fields

3-D Vector Fields

The B field of an MRI will erase any card with a magnetic stripe in the room. If there was a folded steel chair just inside , I was told by the Director of the 7 T MRI in Winnipeg, it would be lethal and sucked in and accelerate to 60 MPH from the magnetic field acting as a force on the iron. When everyone in the tall building had CRT monitors, the display image would implode overpowering the tube's weak magnetic field every time the portable MRI was tested during R&D in the NRC building. Two of my former colleagues helped design it.

Will it affect your application?
Probably not unless designed to sense crosstalk of small changes in inductance but may add or subtract (if reversed) some amount unlike parallel coils like a solenoid not wound like a toroid.

Computing the B1 field of the toroidal MRI coil - PubMed

We present an analytic solution for the B1 field produced in a gapped toroidal cavity resonator designed as a probe for high field MRI. This resonator supports standing TEM waves, so its electric and magnetic fields are identical to those produced by a stationary planar current source with the...

pubmed.ncbi.nlm.nih.gov

 

[ZipZapOuch]

Yes very little B field escapes the torroid, but to say there is none is false.

3-D Vector Fields

3-D Vector Fields

The B field of an MRI will erase any card with a magnetic stripe in the room. If there was a folded steel chair just inside , I was told by the Director of the 7 T MRI in Winnipeg, it would be lethal and sucked in and accelerate to 60 MPH from the magnetic field acting as a force on the iron. When everyone in the tall building had CRT monitors, the display image would implode overpowering the tube's weak magnetic field every time the portable MRI was tested during R&D in the NRC building. Two of my former colleagues helped design it.

Will it affect your application?
Probably not unless designed to sense crosstalk of small changes in inductance but may add or subtract (if reversed) some amount unlike parallel coils like a solenoid not wound like a toroid.

Computing the B1 field of the toroidal MRI coil - PubMed

We present an analytic solution for the B1 field produced in a gapped toroidal cavity resonator designed as a probe for high field MRI. This resonator supports standing TEM waves, so its electric and magnetic fields are identical to those produced by a stationary planar current source with the...

pubmed.ncbi.nlm.nih.gov

Sorry, but the name of the CAVITY used in MRI (and NMR) has, unfortunately, been named a "toroid cavity" but it is really just a hollow solenoid.

The person is placed in the cavity and the elongated donut is wrapped as shown, to create a magnetic field as shown. A Toroidal cavity is much, much, much (did I say much?) different than a toroid inductor.

An NMR and MRI are all about maximizing the applied a magnetic field to the sample. Using a toroidal inductor would be both uncomfortable for the patient to contort themselves into the center of the round cake area of the donut instead of the center of the hollow solenoid. The center of a toroid inductor is all about MINIMIZING the magnetic field (in the center of a circle made by a bunch of coils) .

I am very familiar with MRIs and NMRs and yes, they have large external magnetic fields but a really bad analogy for toroidal inductors.

And, as for your Falstad simulations, those are fine but I've never made a toroid with an air core. The leakage of a real toroid with an iron powder or ferrite core does note lead to any interference with adjacent cores that I have ever scene in real, practical applications.

 

[gary350]

Sorry, but the name of the CAVITY used in MRI (and NMR) has, unfortunately, been named a "toroid cavity" but it is really just a hollow solenoid.

View attachment 144472

The person is placed in the cavity and the elongated donut is wrapped as shown, to create a magnetic field as shown. A Toroidal cavity is much, much, much (did I say much?) different than a toroid inductor.

An NMR and MRI are all about maximizing the applied a magnetic field to the sample. Using a toroidal inductor would be both uncomfortable for the patient to contort themselves into the center of the round cake area of the donut instead of the center of the hollow solenoid. The center of a toroid inductor is all about MINIMIZING the magnetic field (in the center of a circle made by a bunch of coils) .

I am very familiar with MRIs and NMRs and yes, they have large external magnetic fields but a really bad analogy for toroidal inductors.

And, as for your Falstad simulations, those are fine but I've never made a toroid with an air core. The leakage of a real toroid with an iron powder or ferrite core does note lead to any interference with adjacent cores that I have ever scene in real, practical applications.

I forgot to draw the lines on the drawing that indicates metal core. Here is new drawing. Is this the correct way to make toroid inductor drawings?

 

[ZipZapOuch]

I forgot to draw the lines on the drawing that indicates metal core. Here is new drawing. Is this the correct way to make toroid inductor drawings?

View attachment 144475

Yes, that's fine.

 

[Tony Stewart]

Sorry, but the name of the CAVITY used in MRI (and NMR) has, unfortunately, been named a "toroid cavity" but it is really just a hollow solenoid.

View attachment 144472

The person is placed in the cavity and the elongated donut is wrapped as shown, to create a magnetic field as shown. A Toroidal cavity is much, much, much (did I say much?) different than a toroid inductor.

Thanks for the misnomer correction. Shame on me for lack of research

I bought a 1 Tesla water-cooled low rep-rate magnetic pulser for theraputic use worth $2k called the Rejuva Fresh. This I found after I was unable to import a Tesla Stym into Canada from Slovakia worth $25k (used in many physio shops in EU and Asia yet none in North America). The interesting part is the pulse resembles that of a cardiac sinus pulse but faster like those used for electro-stimulus therapy which can sting. This doesn't since I believe it excites the iron properties in blood for deep tissue massage to help health neuropathic and muscular issues before it's too late.

When the magnetic field induces a voltage to exceed the neuron action potential it causes the neuron cell to depolarize which leads to a muscular contraction somewhat proportional to the the pulse strength and rate without the galvanic skin zap.

It works on healing many things and is popular in other countries for fat burning aka body shaping. One hospital in Toronto has a floor model version worth $100k guided by psychiatrists for FDA approved drug-resistance depression, which did not work on someone I know.

It's cool and was good for my wife's knee replacements to speed up post-surgical healing. My dog needed a knee surgery that would have cost me $8k+ recovery therapy costs, which I elected not to do and instead used my magnetic pulser, Black seed oil, Omega 3 and other supplements and now she walks on 4 legs.