primary winding for push-pull converter @100amps, 100kHz

[Tahmid]

Hi all,

Thanks all for your opinions, which I think will help me to have a clear concept regarding different Cores. You see, I am a young learner,still learning and try to learn more from you all. So, from your answers, I could draw the following deductions:

1. Toroid Core without Air gap is good for quality and quiet power transfer and it creates less emi than air gaped E Type Cores. Mostly Toroid Cores, not E or ETD Cores is used in 12v push- pull
application. ------ EVA

2. E Type Cores are having very thin air gap, agrees with EVA regarding advantages of Toroid Core -- Areza and Vena2a.

3. Toroid Cores are mainly used in Audio Field. E Cores are mainly
used in 12v push-pull application throughout the world. Not to bother about the gap as set by the manufacturing Company, just to choose the appropriate one and use it -- Golam.

Now my questions to Areza, what type of Cores you have used in your 1/2/10kw Type inverters you have built as you have mentioned in another post and why that particular type of Core?

Question to EVA-- What type of Core have you used in your 2kw type sine wave/square wave inverter as you have mentioned in different posts? For Commercial production of that type of products, what type of Core you will use and why?

To Golam- Do you have any othe idea regarding Toroid and E Type Core with authentic example?

Hope, all of you will tell me what you think and from your answers, I can formulate a concrete Idea regarding Toroid and E Cores, which are the real backbone of smps arena.

With thanks.

[Eva]

Originally posted by Tahmid

Question to EVA-- What type of Core have you used in your 2kw type sine wave/square wave inverter as you have mentioned in different posts? For Commercial production of that type of products, what type of Core you will use and why?

With thanks.

This inverter has a mains level voltage input and does not require transformers, only massive inductors. At first I used E and ETD cores with an air gap in the inner leg, but this resulted in too high copper losses due to eddy currents and litz wire was required (but still resulted in high copper losses due to the increased ohmic resistance). Then I tried toroids (Arnold's MPP and Micrometals RF materials) and I liked both the performance and the more convenient form factor (plus I was able to use a heavy gauge solid copper wire that way with no penalties).

[areza]

i use both E and ETD type core , as the turn ratio is high and E type are easy to wind,

[jamesrnz]

Originally posted by Eva


This inverter has a mains level voltage input and does not require transformers, only massive inductors. At first I used E and ETD cores with an air gap in the inner leg, but this resulted in too high copper losses due to eddy currents and litz wire was required (but still resulted in high copper losses due to the increased ohmic resistance). Then I tried toroids (Arnold's MPP and Micrometals RF materials) and I liked both the performance and the more convenient form factor (plus I was able to use a heavy gauge solid copper wire that way with no penalties).

eva, i am intrigued by your statement about litz wire vs larger copper (probably) #28/26ish? and lower copper losses in the larger wire.

can you expand on that?

is there some cross over between smaller wire even though the equivalent cross section could be the same and the how it affects the skin effect.

[Eva]

Heavy gauge solid magnet wire results in a good usage of the winding area and low losses. However, this advantage is quickly lost if the wire is subject to strong stray magnetic fields due to gapped cores or the current flowing through the wire has a strong high frequency component. In these circumstances litz wire may result in lower overall losses.

[golam]

Hi Tahmid,

Toroids are compact, and efficient in power transfer and emits less rfi. Its efficiency lies in its internal structure. Toroids without air gap-- this statement is incorrect. Toroids are having internal air gap. Toroids are mainly made of a ferrite alloy known as Mopermalloy, which is having nonmagnetic Molybdenum mixed with it. The Molybdenum acts as distributed air gap within the material itself and hence can transfer power silently, effectively without eddy current loss and it is excellent for dc bias operations also. This internal air gap structured construction can be made in Toroid Type construction only.
---- See, "power supply cookbook" by Marty Brown-- page -237.

Due to high cost, difficulties in winding for mass production and less area for winding for high turn ratio etc. Toroids are mainly used for Inductors. From 12/24/48v, with high output, it is difficult to build Power Supply commercially with Toroids. That is why most of the power supply Cores are of E Type (EE/EC/ETD/ECR/EI etc.) and the reasons are amply clear from Areza's explanation.
Hope, this information will be useful for you all.
With thanks.

[Eva]

They mean MPP toroids, but there are many other materials, including plain ferrite for transformers, of course.

[golam]

There are hundred types of Toroids available in the market. But MPP Types are efficient and mostly used by the knowledable ones. Most of the renowned Companies like Arnold and Micrometal manufacture Toroids mainly for Inductor. But due to its superior quality, Audio manufacturers for power supply, some amatures and smps enthusiast for their testing purpose, make power supply with Toroids. Some times they avoid transformer by using Battery Banks. Nothing wrong in it. But for Mass Production, Commercial Companis use E Type Cores. From low voltage source, like push pull /full bridge topology, Toroids are seldom used.

Thanks.

[Tahmid]

Hi all,
Thanks to all for your answers. Your argument/reargument exposed different pros&cons regarding the operational process/ usefulness of different Types of Cores used in smps like Toroid and E Type Ferrites and many of those were not amply clear to many of us. Special thanks to golam for clearing the misconception regarding Toroid by quoting from the Book of Marty Brown and now I am clear why Toroids are so efficient.
If anybody else having any more ideas, they are welcome to express so that we can learn more.

With many many thanks.

[Eva]

When primary turn counts are low, it's quite hard to get low leakage inductance with E cores. Interleaved windings are quite useful when it comes to reduce leakage inductance, but it can't be done with low turn counts (most off-line switching transformers use interleaved windings).

For example, someone is currently having serious leakage inductance trouble in a push-pull converter with only 3+3 primary turns in another thread.

I use to repair dozens of those 12V mains inverters that use E (and similar) cores for the voltage step-up stage and they are quite inefficient. They are never designed for maximum performance (not even for reasonable reliability in most cases), they would use toroids with series secondaries if they were...