What's the difference between an E-I core and toroid core?

whats the difference between an E-I core and toroid core??

Re: Ferrite cores help

Please , visit www.mag-inc.com/

From here you can download , allinfo that you need about differents magnetics materials and cores.


good luck

garfield

Re: Ferrite cores help

The Basic differance is that an "air gap " can be put in an EI core, where as in toroid there is no provision for puutting air gap.
The magnetic coupling and shielding id good in Toroid.

Now a days toroids are also manufactured using Powder magnetics which has inherant air gap and the same can be used in DC filtering application.

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Ferrite cores help

ive just got 1 question... i have wound same pri/sec windings/same wire guage to an E-I core and a toroid core(both are ferrites)... to my surpirse, using the toriod makes my switching mosfets heat up faster... and the for E-I cores, MOSFTES were not that HOT... WHY??

btw, freq used was 20kHz....

is ferrite shapes frequency dependent???

Re: Ferrite cores help

you have to "Design" your magnetic component properly.
most probably the toroid must be saturating.
even differant ferrite materials have differant power losses.
the operating "flux density" also will cause differances in efficiancy.

Ferrite cores help

so what will i do so that mt toroid will niot saturate?? decrease frequency?

Re: Ferrite cores help

If it is a flyback converter a toroid is not recomended,
Forword also requires very small air gap.

What is your topology, input voltage and output voltage & power.

Re: Ferrite cores help

i am going to use it as an SMPS... 12V in and +45V gnd -45V @4A out.... so whats the difference with E-I core and TOROID core??

Re: Ferrite cores help

because of saturation the core must have an air gap with specific dimension.
toroid cores don't have air gap but ee or ei cores air gap can be specified by the user.
for a reference you can see the abraham i.pressman's "switching power supply design" book. there is complete information about smps and core designing.
hope to be usefull.

Ferrite cores help

is_razi

ive compared an E-I core with and without airgap...ive noticed, the driving MOSFETS heats up a lot faster if an airgap is present, but with the GAP removed, little heating only....

so What really is the difference between TOROID and E-I core??

Re: Ferrite cores help

Both the E-I core and toroidal core you used can be made from the same material, but they also can be made from different material. In my opinion, the latter has higher possibility in your case. If both were built from different materials, the permeability of the both materials will be different. Besides, as the dimension of E-I and toroidal are different, the effective reluctant of the magnetic circuit will be different too.

rx5 said:

ive compared an E-I core with and without airgap...ive noticed, the driving MOSFETS heats up a lot faster if an airgap is present, but with the GAP removed, little heating only?

Click to expand...

This is a good comparison, but initially I thought the mosfet that drives E-I core without airgap will be MORE HOT compared to the mosfet that drives the E-I core with airgap. But after thinking a while, your result is reasonable.

When you compare E-I core without airgap (I assume) to toroidal core (both wound with the same number of turn), the driving mosfet is NOT hot. When you compared E-I core without airgap to E-I core with airgap, the driving mosfet that drives the E-I core without airgap was also NOT hot. So, I assume, in both cases, the E-I core without airgap is never driven into saturation, ie. it works in its linear region.

Back to the E-I core without/with airgap experiment. When we introduce the airgap, we actually increase the effective reluctant of the magnetic circuit, or reduce the inductance of the circuit. When the inductance of the circuit reduced, the current will rise faster and therefore higher and that's why the mosfet that drives E-I core with airgap will heat up.


Well, based on both experiments, ie. E-I core without airgap vs toroidal core and E-I core without- vs with- airgap, I would say that the E-I core that you have, if no airgap, can store higher energy (in magnetic field) compared to the toroidal core you have, providing the number of turns are same for the both cores. However, this does not tell that, in general, 'E-I core' has higher energy storage compared to the toroidal core. It depends on many factors, e.g. material, dimension, airgap length, etc.


If I'm not mistaken, toroidal core provides better performance in term of EMI 'shielding' because the leakage inductance (magnetic field) is lower compared to E-I core. However, this comment requires further confirmation.

Something to add:
The inductance of an E-I core can be reduced as follows:
1) The E-I is driven into saturation. When saturation, permeability (ratio B/H) drops, and therefore, inductance drops.
2) Airgap is introduced into the E-I core. How much the inductance drops is dependent on how much the length of the airgap.

Re: Ferrite cores help

you must offer an extra ampere turn for the air gap magnetization.
i think that the core wasn't saturated so for the ei core the air gap A.T is added to the core A.T and this increase the current.
if the core is saturated the mosfet can be destroyed.

Re: Ferrite cores help

rx5 said:

you must offer an extra ampere turn for the air gap magnetization.
i think that the core wasn't saturated so for the ei core the air gap A.T is added to the core A.T and this increase the current.
if the core is saturated the mosfet can be destroyed.

Click to expand...

Yes ... need extra ampere turn, which can be increased by increasing current or increasing the number of winding turn. In 'is_razi' case, number of winding turn should be increased (which will increase the inductance).

Ferrite cores help

here is the list,

1. E-I core, no GAP, no heat for Mosfet driver

2. E-I core, with GAP, heat from Mosfets

3. toriod 1.25" outer dia, MUCH heat from mosfets..

maybe (i think?) toroids have much magnetic coupling?? than the E-I cores?? i dunno... i even tried re rewinding the toroid and wraping it with a single layer of masking tape, just to make sure its (winding) is insulated from the ferrite core..

Re: Ferrite cores help

rx5 said:

here is the list,

1. E-I core, no GAP, no heat for Mosfet driver

2. E-I core, with GAP, heat from Mosfets

3. toriod 1.25" outer dia, MUCH heat from mosfets..

maybe (i think?) toroids have much magnetic coupling?? than the E-I cores?? i dunno... i even tried re rewinding the toroid and wraping it with a single layer of masking tape, just to make sure its (winding) is insulated from the ferrite core..

Click to expand...

1. E-I core, no GAP, no heat for Mosfet driver
- meaning the E-I core is not driven into the saturation region. The inductance is large enough to limit the current to normal operating level.

2. E-I core, with GAP, heat from Mosfets
- meaning the inductance of the circuit (wound E-I core) drops due to the airgap. As a result, current rise faster and higher and cause mosfets to heap up.

3. Toriod 1.25" outer dia, MUCH heat from mosfets..
- meaning the toroid might have been driven into saturation region. As a result, permeability of the toroid drops and the inductance drops, which in turn will result in higher current.

The (only) conclusion I can make is, in my opinion, the E-I core with NO-GAP has higher energy storage capability than the toroidal core you have. Pls update us.

Ferrite cores help

what do you propose i do so that i dont get the toriod into saturation region?? decrease magnet wire size?

Re: Ferrite cores help

rx5 said:

what do you propose i do so that i dont get the toriod into saturation region?? decrease magnet wire size?

Click to expand...

Decrease magnet wire size means increase the winding resistance. This might or might not help. In my opinion, it will not help much.

Is it possible to reduce the number of turn of the winding? Or, do you have other toroid with larger diameter that could store higher energy?

Ferrite cores help

nicleo,
why would you suggest decrease winidng? a co-forumer of mine told me to in increase my 4T+4T into 6T+6T.. so as not to load much on the mosfets...

sorry, the only LARGEST toroid i could find is only 1.25"... i live in an "uncivilized" part of the earth where parts are hard to find...

Re: Ferrite cores help

rx5 said:

nicleo,
why would you suggest decrease winidng? a co-forumer of mine told me to in increase my 4T+4T into 6T+6T.. so as not to load much on the mosfets...

sorry, the only LARGEST toroid i could find is only 1.25"... i live in an "uncivilized" part of the earth where parts are hard to find...

Click to expand...

My previous comments might not be correct in your situation. Let's discuss more.

1) How many number of winding turn that you wound on the toroidal core?
2) What is the Voltage across the winding?
3) What is the switching frequency of the mosfet?
4) Did the wound toroidal core get hot?
5) How many 1.25" toroidal you have?

Pls update.

Something to add:
Probably in your case, the toroidal core was not driven into saturation region yet. It's just simply that the number of turn was not enough to produce sufficient inductance to limit the current to normal level. Your co-forumer might be correct.

Re: Ferrite cores help

nicleo said:

rx5 said:

nicleo,
why would you suggest decrease winidng? a co-forumer of mine told me to in increase my 4T+4T into 6T+6T.. so as not to load much on the mosfets...

sorry, the only LARGEST toroid i could find is only 1.25"... i live in an "uncivilized" part of the earth where parts are hard to find...

Click to expand...

My previous comments might not be correct in your situation. Let's discuss more.

1) How many number of winding turn that you wound on the toroidal core?
2) What is the Voltage across the winding?
3) What is the switching frequency of the mosfet?
4) Did the wound toroidal core get hot?
5) How many 1.25" toroidal you have?

Pls update.

Something to add:
Probably in your case, the toroidal core was not driven into saturation region yet. It's just simply that the number of turn was not enough to produce sufficient inductance to limit the current to normal level. Your co-forumer might be correct.

Click to expand...

1. 4+4 pri, 16T+16T
2. 12V in, out should be 12V x 4 = 48V
3. 20khZ
4. the magnet wire did not get hot
5. 1 pc 1.25" toriod only

i will try to increase the turns ratio.. maybe 6T+6T pri and 24T + 24T on secondary...

one more thing, are E-I cores and toriods frequency dependent? i mean does driving a toriod @ 20khz, make it more "heating up" ?? or should i increase frequency ??