how do you get trafos to work on DC?

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Not possible.

Transformers require magnetic flux in the core to change in order to create "moving" magnetic field that will induce a current in another winding. If you connect DC to one coil in a transformer, the moment you connect it you'll get a rapidly changing flux and so a spike out of another coil wound on the same core, but once that transient dies out (very quickly) you'll get nothing out of the second coil. In the mean time, unless you limit the current on the coil that has DC connected, you'll be heating up the whole transformer, probably to the point of melting the wires. When the wire finally melts through and breaks open the coil, you'll get another massive spike in the magnetic field followed by another spike in the second coil (assuming it hasn't melted yet).

Look here:
magnetic amplifiers and saturable reactors
Look at the stuff on magnetic amplifiers and saturable reactors.

MR
 
hacknet said:
im got a whacky idea to get power trafos to work n DC? iz this possible?

Even with putting a lot of rigorous effort into it, I don't think you will ever be able to get a transformer to work with DC.

However, if you search the net, you will find designs using ICs, or mosfets, capable of DC to DC conversion.

What is the application? Audio amplifier for the car?

--
Brian
 
hacknet said:
im got a whacky idea to get power trafos to work on DC? iz this possible?

The idea isn't totally crazy. You can transport DC signals through a transformer if it is equipted with a Hall element but this requires active power for the Hall element.

You can transport only AC energy through a normal transformer and that's that! But I must add, as we know of right now. Maybe tomorrow we can.... I'll remember the blue LED (and even white) which were totally impossible to make when I studied semiconductor sience.
 
Maby if you told us what it was for, we would be able to help you some more.

One wild guess:

Anyways, first you need to transform the DC (a car battery maby?)into AC, you can make a nice 50-60Hz AC with a NE555 or similar and power it up with some suitable power transistors. When you got enough power out of your circuit, connect the trafo and be happy. But now you got AC. So, what's the deal? What do you want? No, realy...
 
UrSv wrote:
You just have to find an ideal transformer.

The thingie he is talking about is called IDEAL transformer for which the equation

Vout = Vin * winding_ratio

applies.

Unfortunately we all live in the real world ......... :bawling:



But if Hacknet would let us know what he exactly wants to do we might find a (more or less) elegant workaround.

Regards

Charles
 
Variac said:
Hey old guys:

How about those Model T ignition coils that had a make and break vibrator. Did they just collapse the field or did they actually switch the polarity back and forth?

You could say that a tranformer works thanks to the change in the magnetic field that is made by the primary windings. This makes a 'induction current' (probably a bad translation...) in the secondary coil.
When you take this a little bit further, breaking the connection in that Model T ignition, causes the magnetic field to disappear totally and re-appear again. That definitely is a change in magnetic field and that induces the current in the secondary winding.

Marc
 
trafo's on DC

When I was (much) younger I had also a whacky idea: built transformers with a wooden core to get rid of the iron losses. Guess what? It worked! No more iron losses. Not much of anything else either, though.

Ahh, those days in blissfull ignorance. (Still ignorance, but no longer blissfull).

Jan Didden
 
I did it!

I got DC through a transformer!!!

When I put DC current into one of the primary leads, it came out the other primary lead!

All kidding aside, I'm pretty sure that's about the only way to do it with real world components...

John
 
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