Inductor Safety

[Mastagon]

So as a super newbie question, I was wondering if I need to prevent an inductor from touching the psu casing. I'm modding an atx psu to fit in an itx case, if that's necessary for you to know.  

 

Pictures. And in case it wasn't obvious, I'm talking about the two green things rapped in copper wire. 

[Lolucoca]

Do you mean the transformer? Those are usually pretty well insulated, Just don't cut anything off the transformer.

[Mastagon]

8 minutes ago, Lolucoca said:

Do you mean the transformer? Those are usually pretty well insulated, Just don't cut anything off the transformer.

Recheck the picture. Edited for clarity, as I also might not know what I'm talking about.

[Lolucoca]

You can just wrap them in electrical tape

[QFA350]

5 minutes ago, Lolucoca said:

You can just wrap them in electrical tape

It might get a little toasty. About 2 years ago I made them pretty warm when I destroyed an old 20 pin PSU.

[trag1c]

You will need to insulate those inductors if they're touching the casing. My suggestion would just to wedge something between the inductor and the casing. A small a piece of plastic should do it. 

[Lolucoca]

3 minutes ago, Warning said:

It might get a little toasty

I think it should be okay

2 minutes ago, trag1c said:

A small a piece of plastic should do it.

Yeah, electrical tape

[QFA350]

Generally there is a really thin piece of plastic film under a PSU PCB. Try finding a material like that and insert it between the inductor and the case.

[Mastagon]

Yay. I actually have some of that PCB film. I will do exactly that.

7 minutes ago, Warning said:

 

[mariushm]

There's 110-230v AC going through those copper wires on the inductors (which are insulated with a thin layer of enamel). One inductor is on the live wire, one is on the neutral wire.

If you accidentally scratch the surface, you'll basically tie your mains to earth (the psu  case is grounded, and since the psu case is connected to case your case is also grounded).

Simple fix would be to get some electrician tape and wrap those coils with a layer or two of tape to make them scratch proof , but the downside is they'll overheat a bit (would still be relatively safe).

 

Alternatively, you can just desolder them and replace them with plain insulated thick wire (as thick as the coil wire thickness was).

 

These two inductors and those yellow rectangular capacitors (well just one in your picture, C2 is missing in your power supply) and those tiny blue capacitors between the two inductors are part of a circuit that has the sole purpose of filtering (reducing) the electrical noise caused by the power supply circuitry, so that this noise won't propagate back into the power grid. This noise caused by the power supply can affect radios (for example you may get buzzing or crackling if you have a radio near the computer and you want to listen an AM radio station, and much rarer FM radio stations). In some extreme cases, the electric noise can be strong enough to affect radio based remote controls (think remote control toys).

 

So basically if you're not listening to AM radio stations, you can safely remove those two inductors and reduce the efficiency of power supply's filtering - it won't reduce the performance or efficiency of your psu at all, just makes it less friendly to other devices in your house (radios mostly)

The yellow rectangular capacitors are a special capacitor called X2 which by design basically they can never short out, so if you want you can remove it and just leave the holes there (no shorting with wire like with the inductor)

The blue capacitors are also a very important safety measure, besides helping in filtering the psu noise. They're called Y2 capacitors. They're small and useful, should never desolder them, let them be.

[Huntsman]

By the looks of it, those are common mode chokes. They have mains voltage going through them. Putting them in close proximity not to mention direct contact with anything tied to ground is extremely dangerous. Insulate with plenty of electrical tape or use hot glue to keep them spaced apart.

[Mastagon]

5 hours ago, Huntsman said:

By the looks of it, those are common mode chokes. They have mains voltage going through them. Putting them in close proximity not to mention direct contact with anything tied to ground is extremely dangerous. Insulate with plenty of electrical tape or use hot glue to keep them spaced apart.

Would that be why there was such a large gap between them and the casing in the first place? Originally, the psu looked like this. Would I be able to seal them with heat shrink, or would this sort of think be sensitive to the temporary heat of a lighter? Thanks. When I do get this together, it should help me save a very important 3/4".

[mariushm]

Not only because of that. On one hand it helps if they're close to the vents because they'll be naturally cooled by the air outside at low power when the fan may be turned off but on the other hand they may cause audible coil whine at certain loads so manufacturers don't place them close to vents on purpose. The coil whine is often fixed by using heatshrink over the inductor, or by using silicone caulk/various solutions to fix the coil on the ferrite ring. Insulating tape also helps sometimes reduce coil whine, with the added benefit of adding a layer of protection against scratches and other things.

Manufacturers think sometimes that children may poke things through the vents so they sometimes try to add insulation to those coils but they don't do it just for this reason alone.

More often they're placed in those positions due to the layout of the traces on the bottom of the printed circuit board. Due to lots of regulations, power supplies have to be made in such a way as to be a sensible amount of separation between areas of the power supply where there's high voltage and anything that's low voltage, so basically power supplies are these days like two separate islands on one printed circuit board.

In the case of this power supply, the mains power goes inside in one corner and goes through all those filtering components towards the top (imagine three main large traces going in parallel all the way to the top) where there's the active power factor correction circuit on that big black heatsink at the top (and that huge inductor is part of that circuit) and the bridge rectifier (which converts AC to DC), and then the high voltage DC makes a U turn and goes down into those two large capacitors and then continues down towards the components on those tiny heatsinks right near the large transformer, then the electricity goes through the transformer and hops on the other side of the printed circuit board where there's only low voltage. Everything to the left of the large transformer is high voltage, everything to the right is low voltage. 

So there's three thicker traces and the components and their leads go through the PCB in places near those three traces, and those traces also have to bend a bit to allow other smaller traces in that area to make connections between various parts... that's just where those components ended up at the top after all those connections were made on the bottom of the circuit board.

 

My vote would be for desoldering them completely and replacing them with single solid wire between the two points. If you don't want that, the coolest would be to get some large heatshrink tube and cut pieces big enough to insulate the inductors with it, like you see in the pictures here for example: https://www.techpowerup.com/reviews/SAMA/FTX-800-2/4.html or here https://www.techpowerup.com/reviews/Corsair/RM1000x/4.html

The third and ugliest option would be to just use insulating tape around the inductor. like you see here : https://www.techpowerup.com/reviews/CoolerMaster/V650/4.html or here https://www.techpowerup.com/reviews/FSP/HGX550/4.html (jeesh that's ugly)

 

 

[Mastagon]

Those last two options looked like baked crap, so as I have some mega sized heat shrink, I'll definitely be using that, being that I'm not confident enough in my electronics skills/knowledge to do that (though I understand its a simple concept.) The case I designed to use this PSU in was made with good airflow in mind, so that along with the psu fan being speced to move 153 CFM, my layman's understanding has me thinking that heat from the now sealed inductors won't be an issue. 

 

Thanks loads. Now I can still use the PSU whose warranty I have definitely voided the hell out of. 

[Huntsman]

5 hours ago, Mastagon said:

Would that be why there was such a large gap between them and the casing in the first place? Originally, the psu looked like this. Would I be able to seal them with heat shrink, or would this sort of think be sensitive to the temporary heat of a lighter? Thanks. When I do get this together, it should help me save a very important 3/4".

Common mode chokes are pretty robust. They don't heat up much so they don't really need airflow. The only thing they need is separation from other components to avoid shorts. Heat shrink should be fine, just don' apply heat for too long as that would either melt the plastics or melt the glue that sticks the ferrite cores together.

[Mastagon]

5 minutes ago, Huntsman said:

Common mode chokes are pretty robust. They don't heat up much so they don't really need airflow. The only thing they need is separation from other components to avoid shorts. Heat shrink should be fine, just don' apply heat for too long as that would either melt the plastics or melt the glue that sticks the ferrite cores together.

Thanks brother. It turns out I need larger gauge heatshrink, which I just ordered and should be here by Monday. I'll throw up some picks of my finished product then, along with how it fits in the case. Should be fun times.