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| Connecting Parallel Transformer Primaries with Faston Connectors |
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| grbk:
I'm wiring up a mains transformer inside a metal chassis and want to make sure I'm following best practices for safety & reliability. This is for a personal project, nothing commercial, and low power, but I do want to know what the "best" way to do this is. Ideally any solution would pass a UL certification, etc. The transformer has two primaries, and I'm on 120V mains, so I'm connecting them in parallel. I'm using crimped Faston/quick connect terminals to make the connections. I have line/neutral from the IEC inlet to a front panel power DPST switch, with faston connectors on the inlet and the switch. But now I have two transformer primary wires to connect to each tab on the switch. How do I connect two transformer primaries to a single tab, preferably with crimped faston connectors? To be clear, I understand in theory how to connect the primaries in parallel (I know which wires need to be connected together). My question is how to make the physical connections. I see several possibilities, but I don't love any of them and I'm hoping I'm missing an obvious solution: * Ditch the crimped terminals and solder the wires directly. I worry about the reliability of the soldered connections to freehanging wires, but mostly this is not an option because I specifically want to be able to swap out the transformer. * Crimp both primary leads into a single faston connector -- this seems dubious. * Crimp both primary leads into one side of a butt splice. Crimp the other side of the splice onto a single wire, which then gets crimped into a faston connector, which connects to the switch. For some reason this seems slightly better than 2) above, but it's basically the same in that I'm still crimping two wires into a single terminal. * There are all sorts of freehanging 2-to-1 wire splice options out there. For some reason these still seem a bit amateur/how-ya-doin', but maybe I'm being unreasonable? * make the connections with a chassis mounted terminal block and spade terminals * make the connections with a PCB -- overkill to design a PCB and get it fabbed, plus now I have to think about PCB creepage distances. * Edit: I suppose I could use a 220V/120V selector switch. That seems superfluous for a device that will only be used by me. * "Piggyback" and two-to-one faston terminals exist, but most of them are uninsulated. I'm using an earthed metal chassis, so uninsulated is not the end of the world, but I'd still prefer an insulated solution. Still, this might be my best option. Are there any better solutions that I am missing? Are there any resources (books, articles, etc.) that are helpful for this kind of mains chassis wiring that anyone could point me to? I've found some information in Art of Electronics and in Doug Self's Power Amplifier book, but neither are as comprehensive as I'd like. One further question: I've seen several recommendations to put an X2 capacitor across the power switch. Is this best practice? How would one make the connections? Soldering it would be easy, but that seems incompatible with using Faston terminals. Thanks for any advice. |
| Gregg:
There are plenty of DIN rail mount terminal blocks that would suit your purposes. That is if you have room in your enclosure. |
| grbk:
--- Quote from: Gregg on March 09, 2019, 05:32:40 pm ---There are plenty of DIN rail mount terminal blocks that would suit your purposes. That is if you have room in your enclosure. --- End quote --- Thanks for the suggestion. I knew very little about these so I just did some reading. They seem very useful. I think they will be too big for this project, and perhaps overkill for the limited number of connections I'm making, but I'll keep them in mind for future projects. |
| helius:
You could also use Wago 221 or 222 lever-lock connectors, either free-hanging or mounted to a rail using Wago system carriers. |
| Benta:
The "piggyback" solution is the right one, with heat-shrink insulation if needed. |
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