Does a ferrite core primary of toroid transformer saturate for lower efficiency, at a pulse peak amps current at low 34%duty cycle, or at the overall much lower average current level over one cycle? Ferrite toroid has full flux path, just as a 2 piece ferrite core set. However, the 2 piece unit can have paper spacer in between 2 halves to reduce inductance and saturation possibility. AI is not always correct and says Peak current dictates saturation even at low duty cycle. Toroid FT240-31 material. 7 peak amps vs milliamps Average .

I was also told, -- Magnetic saturation can occur with low duty-cycles. It’s all a matter of applied voltage and on-time. The ferrite material doesn’t store energy. The energy is stored in the magnetic gap, which is a requirement with soft ferrite cores in circuits where energy is being transferred as the field collapses. For some toroid cores, magnetic and non-magnetic materials are mixed to form a distributed gap within the torus.

 

Missing information;
-Cross section area
-Frequency
-Applied Volts-Seconds
-Number of turns
-Saturation flux and the remanence

 

Missing information;
-Cross section area
-Frequency
-Applied Volts-Seconds
-Number of turns
-Saturation flux and the remanence

Main question was for an Either / Or answer , in general, not a specific circuit. Peak / or Average current as used electronics formulas.

 

Got it!

Simple answer: in a transformer the applied volt-seconds are the parameters that saturate a core. As you mentioned in the second paragraph of your request.

 

Toroid FT240 type 31 material wrap 20 turns and build an LC resonant circuit close to your frequency. Calculate the permeability. Try not to over think this.
As the core saturates what happens to permeability? see below, The PWM equation might be alright but characterize what you have.
34% duty cycle lowers the current and sure that is the low end . But what is the VA rating? What size wire will you need.
When you know your core's permeability, then transformer design begins to take shape.
Controlling and Preventing Core Saturation in Inductors - Technical Articles

 

Flux is equal to Magnetomotive force divided by reluctance (Hopkinson's law)
Reluctances add up when they are in series (like resistances), so the total reluctance is the reluctance of the core plus the reluctance of the gap.
Reluctance is the reciprocal of permeance. The permeance of the core is listed as the Al value.
Magnetomotive force is equal to current multiplied by number of turns.
Flux density is equal to flux divided by cross sectional area.
so YES. TOO MUCH CURRENT CAUSES SATURATION. The frequency is irrelevant.

And Yes, magnetic saturation can occur at low duty cycles. Current is equal to the applied Volt Seconds divided by the inductance. (as per @schmitt trigger in post #4)
and yes, the energy is stored in the gap not the core
and yes, you can get distributed gap materials, which used to be iron powder, but now distributed gap ferrite is also available.
Iron powder has a much higher saturation flux density, but higher losses, so is more suitable for high current supplies with low ripple current, because the losses are proportional to the peak to peak flux excursion, not the absolute flux density.

 

https://www.google.com/search?q=ferrite+core+impedance+versus+frequency+vs+pulse+shape
also returns https://www.tdk-electronics.tdk.com...270f5d5dbf1efec233/pdf-generaldefinitions.pdf
https://www.we-online.com/components/media/o799203v410 ANP129a_EN.pdf

 

Flux is equal to Magnetomotive force divided by reluctance (Hopkinson's law)
Reluctances add up when they are in series (like resistances), so the total reluctance is the reluctance of the core plus the reluctance of the gap.
Reluctance is the reciprocal of permeance. The permeance of the core is listed as the Al value.
Magnetomotive force is equal to current multiplied by number of turns.
Flux density is equal to flux divided by cross sectional area.
so YES. TOO MUCH CURRENT CAUSES SATURATION. The frequency is irrelevant.

And Yes, magnetic saturation can occur at low duty cycles. Current is equal to the applied Volt Seconds divided by the inductance. (as per @schmitt trigger in post #4)
and yes, the energy is stored in the gap not the core
and yes, you can get distributed gap materials, which used to be iron powder, but now distributed gap ferrite is also available.
Iron powder has a much higher saturation flux density, but higher losses, so is more suitable for high current supplies with low ripple current, because the losses are proportional to the peak to peak flux excursion, not the absolute flux density.

OK thanks. I have the ferrite ring toroid that core cannot be adjusted, and also 2 piece U +U ferrite where thin paper can bridge the 2 gaps. That reduces the inductance down slightly, but the iron powder toroid core has very little inductance, requiring huge number of turns. Toroids are mostly for low turns windings. Then there are the different costs involved.

 

OK thanks. I have the ferrite ring toroid that core cannot be adjusted, and also 2 piece U +U ferrite where thin paper can bridge the 2 gaps. That reduces the inductance down slightly, but the iron powder toroid core has very little inductance, requiring huge number of turns. Toroids are mostly for low turns windings. Then there are the different costs involved.

If you have a Dremel and a diamond saw, you can "adjust" your ferrite toroid!
I don't recommend it, because it then becomes a real pain to wind as the wire slips through the gap.
There are many different grades of iron powder, with quite a spread of different permeabilities.
What type of supply are you thinking of designing?

 

If you have a Dremel and a diamond saw, you can "adjust" your ferrite toroid!
I don't recommend it, because it then becomes a real pain to wind as the wire slips through the gap.
There are many different grades of iron powder, with quite a spread of different permeabilities.
What type of supply are you thinking of designing?

I intend to use 2 piece ferrite with gap, for CDI step up small transformer with PF capacitors discharging into primary . Trying to duplicate small circuit from 2008, called Capacitor70, that increases existing voltage from source. There isn't any other way to do it. The Ferrite toroid would require too many adjustments to work, and avoid saturation. Original unusual circuit used small GRAY ferrite toroid, low turns, on about 15 cycles, and was working, and duplicated by 3 other people. 1st adjustable spark gap fires pulse and charges caps same time, that discharges a primary, firing secondary side through 2nd gap. 3:1 step up . Ferrite has WAY higher inductance capability than iron powder, and a gap just lowers inductance somewhat, still usable, and better than distributed core iron powder.

 

I intend to use 2 piece ferrite with gap, for CDI step up small transformer with PF capacitors discharging into primary . Trying to duplicate small circuit from 2008, called Capacitor70, that increases existing voltage from source. There isn't any other way to do it. The Ferrite toroid would require too many adjustments to work, and avoid saturation.

Depending on the circuit, some step-up circuits work best with ferrite and some work best with iron powder.

 

Consider that if most energy were stored in the air gap, that most transformers would use air cores because of the cost reduction. There is certainly a purpose for air gaps, but it is not to store energy. The "best choice material" for any transformer depends mostly on the operating frequency and the power level, as well as the waveform. The required inductance/reactance also is a consideration. Other have mentioned that and they are correct.Adding an air gap can avoid saturation, but it also reduces the efficiency.

 

The use of a specialized air gap core has some applications for current management. The length of the gap causes a fringe effect.
Some have experimented with small scale models. Having variable permeability / core saturation example a welder long ago literally cranked
his welding machine up or down according to the material thickness of the weld. When a machine has an intermittent load the
the air gap core made of laminated 3% Silicon steel is slide adjusted for an anticipated load range. The welding machine duty cycle
had a meaning of how long you could weld 10 minets. Example 60% duty cycle meant you could drive the transformer for 6 minets in a 10 minet period.

 

Consider that if most energy were stored in the air gap, that most transformers would use air cores because of the cost reduction. There is certainly a purpose for air gaps, but it is not to store energy. The "best choice material" for any transformer depends mostly on the operating frequency and the power level, as well as the waveform. The required inductance/reactance also is a consideration. Other have mentioned that and they are correct.Adding an air gap can avoid saturation, but it also reduces the efficiency.

Energy is stored in the gap. Not the core.The purpose of the core is to conduct the flux to the gap. We had this conversation a few weeks ago. Here is the physics (for a second time)
https://phys.libretexts.org/Bookshelves/University_Physics/University_Physics_(OpenStax)/University_Physics_II_-_Thermodynamics_Electricity_and_Magnetism_(OpenStax)/14:_Inductance/14.04:_Energy_in_a_Magnetic_Field
The energy stored in a magnetic field is inversely proportional to the permeability.
Also, there is almost no loss in magnetising the air, whereas a large proportion of the energy lost in an inductor comes from magnetising the core.

 

Thanks Ian0 I missed that it was a follow up question from an earlier post and it had been answered.

The general subject and many useful references are presented link below on understanding air gap core transformers.
An Encyclopedia on Magnetics is helpful as the fields of physics get questions sometimes require a different presentation format than a forum.

Air gap [ Encyclopedia Magnetica™ ]