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homemade flyback transformer

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haxor5354

Wed Jan 05 2011, 06:16AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

just finished winding the HV secondary, it has 10 layers of copper wire salvaged from a MOT and each layer has about 50 wounds. for every layer of wire, theres a layer of tape for better insulation. i was surprised by how much current the HV secondary was outputting

I tested it with the ZVS driver running off of 24 volts. not sure if I should try 36 volts. the output voltage seems pretty low compared to "proper" FBTs because the the electrodes have to come very close together to ignite the arc. once its ignited it can stretch over an inch.

does the frequency of the ZVS driver have dramatic effects on the FBT's output voltage?
and also, less primary windings mean more voltage on the secondary? or is it the complete opposite?

radhoo

Wed Jan 05 2011, 04:13PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

you can go for 4+4 instead of 5+5 to increase the voltage but don't expect more then 4-5KV with 500turns. You can also use a different driver, like a PWM driver, to increase the output a bit.

I also did this, here is a 2500turns secondary:

Some time later, with extra care, I tried another approach, wounding it a turn next to another like in a tesla coil, and with the next layer starting from the same end to reduce intra-layer capacitance:

with better results.

If high current is what you need, simply use ticker wire and you can make a soldering station, a point-soldering tool or a general purpose inverter:

Ash Small

Wed Jan 05 2011, 06:07PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

The more current in the primary, the higher the voltage in the secondary (I think)

The higher the frequency, the higher the current in the secondary (this only works up to the optimum frequency of the flyback, which is generally dependant on the type of ferrite the core is made from)

Kolas

Wed Jan 05 2011, 07:55PM

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

with flybacks driven from push pull inverters it's basicly a simple transformer. in other words the output of the secondary is based on the ratio of volts per turn on the primary.
with home made flybacks, low voltage output is to be expected, you need about 2000 turns to start seeing reasonably high voltage. Home made transformers like this generally lack insulation, and the type of insulation/frequency you run it at will determine it's life. In short to wind your own flyback is to eventually need to wind another.

Plasmana

Thu Jan 06 2011, 04:36PM

Registered Member #3108 Joined: Thu Aug 12 2010, 05:37PM
Location: Worthing, England
Posts: 72

I wouldn't expect much voltage from 500 turns of wire, the 'proper' flybacks had many thousands turns of wire on their secondaries. If you are going to make an flyback with a few thousand turns of wire, make sure you put it under oil otherwise it will arc over internally (learned that the hard way).

Also, how did you managed to get the whole secondary core out of an MOT?!

quicksilver

Thu Jan 06 2011, 07:36PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

SOME of the smaller ones don't have the spot-weld going deep and COULD be divided via a wedge-type device (sharp chisel).....That's the only thing I could even imagine....

ubuntupokemoninc

Thu Jan 06 2011, 11:33PM

Banned on 1/22/2011 for repeated rule violations after multiple warnings.
Registered Member #3299 Joined: Sat Oct 09 2010, 08:11PM
Location: Bantown, USA
Posts: 220

does it heat? when i run my zvs at 1kw (the flyback is in oil) the oil boils in a matter of 45 seconds!

haxor5354

Fri Jan 07 2011, 04:20AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

ubuntupokemoninc wrote ...

does it heat? when i run my zvs at 1kw (the flyback is in oil) the oil boils in a matter of 45 seconds!

the primary and core gets warn after 5 or 6 minutes, but the secondary is only slightly warmer than it should if sitting at room temp

does the primary heat up or secondary or both?

ubuntupokemoninc

Fri Jan 07 2011, 11:37PM

Banned on 1/22/2011 for repeated rule violations after multiple warnings.
Registered Member #3299 Joined: Sat Oct 09 2010, 08:11PM
Location: Bantown, USA
Posts: 220

well the primary heats like hell cuz i cant fit big wire on the core, and plastic gets "gooey"

I lost count of how many flybacks i've killed

haxor5354

Sat Jan 08 2011, 02:20AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

does anyone know what that piece of plastic that gaps the 2 U shape core does? i lost 1 of them and i just cut a plastic card to gap it again.

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