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Mario Pankov 19th November 2009 03:23 PM

Output transformer cores
 
I was looking at transformer cores for the past few months as I am looking to start winding my own trafos. The M6 silicon steel has been a favorite to many people - it is cheap, not that hard to find and has good parameters. However, I was looking into something more exotic, no matter what the price would be.
What I found so far is a material called Metglas Magnetic Alloy 2714 which shows superb qualitues - it has the lowest core loss, permeability is many times higher than M6 so it should allow a much smaller core size, which means a reduction in the turns radius and thus less losses in the copper. This material also has a freq range up to 250Khz and is often used in aviation and medicine transformers. There are a few companies that offer C-core laminations of this material. To me it looks like the ideal core material, any thoughts?

WBS 19th November 2009 03:51 PM

C-core is the way to go if you've got the dough.

smoking-amp 19th November 2009 05:02 PM

Max flux density and power at the lowest audio frequency sets the core size, not the permeability. Metglas 2714 only has .57 Tesla saturation (annealed) and only .25 Tesla un-annealled. So this will require a 3 to 6 times larger core area than M6. (which translates to 5 to 14.7 times the core volume of M6)

Bandersnatch 19th November 2009 07:31 PM

hey-Hey!!!,
I'd go for 49% Ni stuff. I suspect I can get C-cores in the size I want; it is unavailable in the larger sizes of scrapless E-I. Near the saturation flux density of M6( or M4 and M3 for that matter ), higher permeability and lower loss than 3.5% Silicon steel. Nice stuff indeed, though I suspect it'll be $60-70 per pound...:) I'll be using it in a coil design set for a 2.5" stack of 1.5" center leg width scrapless E-I.
cheers,
Douglas

Matt BH 20th November 2009 12:21 AM

Hi Mario,
Could you let us all know where you can get the Metglas stuff. I have a pair of M6 c-cores but as two they are big enough for one transformer but I need two. I have been thinking about winding my own output trannys for a while, even built a lathe type lash up with a counter etc. The cores I have a are marginal after doing all the math. I really dont want to wind some trannys on the off chance. Even after measurement with my cores. I get 300W with the two at 50Hz with minimal distortion. So c-cores can be a fair bit smaler for push pull. Langford Smiths papers show this but there is very lttle info out there about it.
Cheers Matt.

Mario Pankov 20th November 2009 07:31 AM

There is an English company that supplies these materials. I do not have the pricing as I have not figured out what would be good as material.

I did a mistake when pasting the Metglas number, it is the 2605SA1 and I found a work by a Swedish aircraft electronics designer who said they are best for transformers used in the Grippen aircraft. What I am looking is this:

http://www.amorphousmetals.com/products/page5_1_6_2.htm

alexberg 20th November 2009 02:25 PM

Quote:

Originally Posted by Mario Pankov (Post 1987100)
There is an English company that supplies these materials. I do not have the pricing as I have not figured out what would be good as material.

I did a mistake when pasting the Metglas number, it is the 2605SA1 and I found a work by a Swedish aircraft electronics designer who said they are best for transformers used in the Grippen aircraft. What I am looking is this:

Powerlite C-Cores

What is the purpose of using low loss cores? Losses are extremely small - you will be getting a lot of unwanted resonances... unless you know for sure how to deal with it.
BTW
1.Package factor is less than 0.8.
2.I would not recommend flux density more than 1T.
In respect to iron cores amorph core will be at least two times bigger by the volume.

Arnulf 20th November 2009 04:01 PM

Quote:

Originally Posted by Mario Pankov (Post 1987100)
I found a work by a Swedish aircraft electronics designer who said they are best for transformers used in the Grippen aircraft.

Grippen is a fighter plane, not a tube amplifier ;)

Jacques Merde 20th November 2009 04:38 PM

Have you considered Vanadium Permendur (2% vanadium, 49% cobalt and 49% iron), AKA Hiperco 50? It has a significantly higher saturation flux density of about 2.4T compared with 1.5 for the Metglas 2605SA1.

Hyperco 50 datasheet

I noticed that for the 2605SA1 the material properties looked great, but the published B-H curve in the C-Core Technical Bulletin for the AMCC6.3 C core did not look so swell. Specifically, B vs H is not very linear at reasonable inductions. :(

That high value of permeability on the material data sheet sure looks good though.

kevinkr 20th November 2009 05:34 PM

OT:
Jacque Merde.... As a user id, clever...:rofl::rofl::rofl:


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