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Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
Hey all, I got a ferrite core transformer (not the flyback) from a monitor. I managed to salvage the bobbin and the ferrites successfully, and was wondering, how do you usually tell how much power the core can handle?
It's a pretty sizeable transformer, and its got a logo and some numbers on the top.
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
Most CRT monitors consume about 100W in operation. I've measured my 22" CRT at anywhere from 80-120W depending on resolution and what's on the screen. These transformers are almost always run in flyback topology supplies which accounts for their relatively large size for the power level. They are nice big cores though, should be good for a few hundred Watts driven push-pull. Useful for all sorts of power supply applications, the output voltage only depends on the secondary turns count.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
so could i wind a coil and put it onto the middle part of the E core and add some primary windings on one of the other sides?
No, because then the other side would be magnetically shunting the windings. If you have to ask the question, then you probably won't understand the explanation of why it's bad, but this type of shunt would be bad.
You *could* put it on the middle part of the E core and add two identical primary windings, one on each of the other legs. This reduces the length of copper needed slightly, but that's rarely the most important loss in the transformer. It gives you a little flexibility in that the primaries can be used in either series or parallel, but you must use both identically, you cannot drive them in push-pull, as they're not coupled properly.
A transformer wound like this will have singnifcantly poorer coupling (which is bad) than the conventional way of winding it with both primary and secondary on the centre leg. If you put two primaries on in the conventional way, you would still have the series or parallel flexibility, *and* you could drive them push-pull if you wanted to.
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
Why not just wind it the way it was originally wound? Insulate the layers adequately and you should be fine. Alternately you could make a partition to divide the bobbin and place the two windings side by side, that's a common technique for providing improved isolation.
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Ferrite Core from Monitor
. The ferrites in monitors and TVs usually handle from around 100-400 watts in normal use.
