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transformer winding

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Dr_Doggy

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hi, just wonderin if i can wrap wire around a bar magnet , or do i need a doughnut magnet(closed loop) ,, also what kind of losses would I suffer from using cast iron as a core ?
 
You don't use a magnets for transformers. Cast iron is probably one of the worst transformer materials you could use, what kind of transformer are you trying to make?
 
Its better to buy pre-made transformers, than to attempt to make your own. Unless its for a specialty project and you can't find the specific type you are looking for.
 
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You need a closed magnetic loop for an efficient transformer. You need laminated soft magnetic steel for transformers up through the audio range and generally some type of ferrite material for frequencies above that. Any form of solid iron or steel for a core will give high eddy current loses in the transformer, which will generate heat.
 
DO you have a particular need for one that you wna to build or is this a just for fun learning project?

If your just looking to experiment pick up some old battery chargers or microwave ovens. They are the simplest and easiest transformers to rewind and many have the primary and secondary windings side by side.
For HF rewinds the small toroid inductors from the line filters can work rather well with very little work involved in rewinding one of them. Or the ones you can find in most electronic devices can be reworked too!

But for application specific there are many variables that have to be acounted for before one can be hand built.
 
lol, ya , i luv these flybacks, but its too big(volume), all i really want is the 2ndry coil and the core, but the blodys all glued together, so i can get the secondary out ok, but i keep shatterin the core, ,, i wanna actually set a few up in series on the same core, and form my own primary loop.


In another expirment i had a 57khz flyback(running off a 2n3055 + sine generator) , when i took the leads from the primary coil , and put them on the feedback loop , the resonant frequency went up to 420khz , and my voltage potential trippled, this also cut my current draw from 0.50 A (which is typical for flybackdriver circuit) to 0.08A, however i need to resort to plan b since im haveing problems with a 5-9v clock ringing that fast (iv used 555 timers and hex inverter clks)
 
what about a car ignition coil, i just took one of em apart and its core was composed of straight metal plates!?!
 
Are you sure that's an ignition coil? This is how 'normal' ignition coils typically look.
**broken link removed**
 
The laminated soft iron core does look like a stack of straight metal plates.
 
thats the one!

ya thats it alright , but heres a pic of the core i extracted, to me they look like 1mm thick stainless steel rods, all stacked together, but again , doesnt the core need to be in a loop?
 

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The core of an ignition coil is a solenoid (straight) That's why you can pick them up on an AM radio, the magnetic loop isn't closed. Proper manufacturing of a toroid or pot core ignition coil would be prohibitively expensive. You should have had a loop of wire around that coil. Maybe attached to the case itself.
 
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so if i wound a primary ,secondary and feedbak loop around that core it would work ok?
 
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