Why dont wall transformers have holes?

When i was making my homebrew hot wire for foam cutting, i noticed my 17V low amp transformer ((wall-mount) was getting really hot. So I question to my self, why the heck don't these things have holes? Would it be safe to get a project box from radioshack, Cut out the transformer, and if i want install a fan to keep it cool? or does dust wreck it? Also, theres no way to do hotwires and keep the transformers down right.. i mean its basically a short circuit, as why you try to make the wire hot to cut foam...

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westfw9 years ago
  • 1: They're not supposed to get too hot.
  • 2: They don't contain components that are sensitive to heat anyway. Semiconductors change properties as temperature changes, and eventually get damaged just from the heat. Not so iron cores and copper wire; the first thing to go will probably be the insulation on the wire.
If it's met proper safety approvals (there are some suggestions that cheaper imported units have "forged" approvals), then it's probably been tested to ensure that it does not get "dangerously hot" even under pessimal overload conditions...
westfw .. well it can't get any hotter once you burn out the thermal fuse, hidden under the tape over the windings, so if it's approved you shouldn't be able to catch it on fire or for that matter melt the case... And Killa-X Why not just get a bigger transformer or rewind a microwave transformer and build your own box... And for a hot wire cutter the old trigger operated weller soldering guns (( 100 watt area )) work awesome and I have not seen one over heat, even with the wire glowing cherry red, the wires don't last long though....
Juklop9 years ago
Sounds like it just needs more Energon.
guyfrom7up9 years ago
it means you're oversdirving the transformer, that's not good for it
overdriving*
Killa-X (author)  guyfrom7up9 years ago
ya but all heat things do that. plus transformers are allow to get way over the "too hot to touch" limit, as this stays "warm to the touch" I still wish to know why transformers dont have vents.. i never seen ANY transformer that doesn't get warm.
...I still wish to know why transformers dont have vents...
Magnetics mostly. The idea with a power transformer (as opposed to other types) is to keep the magnetic field close to the windings and strong, thus the iron core in the wrap-around shape, and laminated cores generate less heat thus the "impossible to take apart and reassemble" design.

To get proper cooling, something would be to have an extension of the core to carry the heat away. You could shape an edge with fins like a heat sink, which would be an interruption of the idealized "magnetic circulation" thru the core and may generate heat. Other possible extensions like a bar would reduce efficiency by drawing magnetism away from the windings and other effects due to more mass being magnetized, besides inducing currents in nearby wires and components. Bolting on something like an aluminum heatsink would be better with minimal issues, you can try it with your own projects, however...

The concept of a wallwart is a minimal and safe package. They generally don't use holes to protect the electronics from moisture and dust, etc. It is possible to engineer a housing and heatsink that would have venting only for transformer cooling with the transformer itself and any electronics still sealed away. For about 2-3x the cost.

So the answer is, because wallwarts are cheap throwaways.
what forgesmith is mostlyt true: -most are laminate core because it reduces eddy effects -eddy creates heat -the plastic has nothing to deal with magnetism -a heatsink would be fine, most of the magnetism is confined in the core -only reason wallwarts are put together the way they are cause it's cheap, no screws, a bit of glue
The thing is, that the wires inide the transformer will melt, thus cuasing you great greef, meaning, it will break just get a hacksaw, and cut some big holes it the case, the diodes might burn out, and no one like that : )
NachoMahma9 years ago
. The lack of holes is probably for safety. Wall warts are usually mounted at just the right height for small children to stick something in any holes. . Your project will be safe as long as you don't touch any bare wires. Normal house dust won't harm a transformer.