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Trial method of flyabck core fabrication

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Kolas

Sat Apr 29 2006, 02:44AM

Registered Member #102 Joined: Thu Feb 09 2006, 08:15PM
Location: Raleigh, NC
Posts: 169

Ok, hi guys
I was recently thinking of a way to get a larger core then the winky dink cores you can obtain in a TV flyback, that could handle the frequencies i like, but stand up to high wattages.
My solution: take 4 90 degree PVC fittings of choice size and then cut pipe to fit.
You should end up with a square.
This is when you go find about 5 old cores from your dead flybacks, and crush them. That's right, i said it, hit them with a hammer. once your ferrite is powdered, fill the square with it.

Vuala, you have a realitivly large flyback core.

Sound fesable?

Kolas

williamn

Sat Apr 29 2006, 02:53AM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

I tried it. Yes it works. I used ground up ferrite torroids. Check the archives, I believe I started a thread on it.

The Wumpus

Sat Apr 29 2006, 10:24AM

Registered Member #325 Joined: Fri Mar 17 2006, 12:42AM
Location: Turku, Finland
Posts: 55

Instead of smashing the flyback cores, how about taking those large ferrite cones behind the deflection coils on CRTs? They are not really useful for anything else anyway.

Dr. Dark Current

Sat Apr 29 2006, 12:12PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

How fine the ferrite powder has to be for it to actually work? Does it need to be pressurized? sorry, I cant find the old thread.

J.M.

robert

Sat Apr 29 2006, 12:18PM

Registered Member #188 Joined: Thu Feb 16 2006, 05:18PM
Location:
Posts: 67

You will get a huge air gap this way.
I think it wont really work well compared to a real ferite core.
If interested, i could organise a second group buy of large U cores (150x90x30mm).

Marko

Sat Apr 29 2006, 12:22PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I just got an idea for it some time ago, cores from CRT deflectors seem good idea as they most usually need to be smashed anyway to get them out of all tthe epoxy.

I was thinking o mix the ferrite powder with poliested and dry it, getting a big, compact core.
I think to use it to make an enormous core, bigger than any that can be bought and use it for a monster inverter like steve ward's CCPS/solid state pole pig)

The only problem I see that ferrite particles, either just powdered or mixed with some poliester, will not be close as they were in real core and it may kill some preamblity of the core, but I don't know is this going to be significant anyway.

cheers..

Sulaiman

Sat Apr 29 2006, 06:23PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I've had a 'play' with recycled ferrite
(pot cores, EI cores, rods and cry deflection yoke ferrite)
I pulverised it in a mortar and pestle
(NOT GOOD - lots of dust)
(also, polyurethane varnish never seems to go hard in bulk

)

Very good for a flyback transformer PROVIDED
the primary and secondary are wound one over the other
-not on separate sections.
Also I used it in the form of a continuous ferrite core
(in pvc of course)
Not easy to change/modify windings.
Overall not worth it so I bought 1"x1"x4" ferrite blocks off eBay

Marko

Sat Apr 29 2006, 07:06PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Powder can be easily fixed with poliester or epoxy goo but I don't know is this going to lower the preformance of the core in reality.

And I think ths is really worth for making a giant transformer, with the power of pole ig but many, many times lighter and cheaper.

Sulaiman

Sat Apr 29 2006, 07:16PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Firkragg,..That's where I had problems (small-scale/power)

If you wind a flyback with closely coupled coils
the loose ferrite (like iron powder) has a low overall permeability
but works well for energy storage/flyback.

As a power transformer
1) difficult to get enough volts/turn
2) very high leakage inductance
i.e. definately not a good choice'
from memory.

Marko

Sat Apr 29 2006, 07:30PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Iron powder core has actually pretty good preamblity, but it's drawback is that ferite particles tend to suffer from significant eddy currents that makes them very lossy at frequencies we operate them at.

I never seen commercial ''ferrite powder' core and I don't think you can compare it with anything. William, how did you use that home-made cores, (how much power, etc), were there any problems, does it really matter that particles are now few micrometers more away?

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