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Can two inputs make an isolation transformer?
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001:

--- Quote from: Hero999 on December 11, 2018, 10:33:25 am ---Why not use a toroidal construction for a medical grade isolation transformer?

There's an earthed screen between the primary and secondary, which both offers additional protection and prevents capacitive coupling between he secondary and primary windings.

--- End quote ---

Yea

And it adds capasitance between sec and ground so still shock hazadrd
Gyro:

--- Quote from: scuzzyTerminator on December 11, 2018, 02:51:49 am ---
--- Quote ---It doesn't sound as if you are that experienced in mains wiring from your previous replies, if so, please be very careful and ask for advice. Be safe.
--- End quote ---

I'm actually less experienced than it sounds. I'll be careful. The best thing I got going for me is that mains freaks me out.

Thanks for all your help.

--- End quote ---

That's a useful defense mechanism in keeping you safe. Your best bet would be to properly mount it in a metal case. For the mains input it would be best to use an IEC connector to avoid the trip hazard of a trailing mains lead when carrying. The Input ground pin should be wired directly to the case, ensuring good connection with a tag, serrated washers and lock nuts. The protective ground wire from the transformer and the ground from the Output socket should go to the same point.

The Input Live connection should go straight to a panel mounted fuse holder, sleeve all connections. Try a 3.15A Slow blow fuse to cope with input surge current. You may want to add a double pole switch and neon indicator, of just go straight to the transformer primaries, wired as the diagram. You could either use soldered connections with plenty of heatshrink sleeving or a mains rated terminal block.

The secondary wiring is the critical part for a safety isolating transformer - if either of the output connections accidentally comes into contact with the case (ground), it will completely nullify the purpose of the transformer. Wire the secondaries in parallel (0-0, 115-115, assuming your mains is 110-115V), straight to the output connector. If you need to extend the wires then use multiple layers of heatshrink sleeving on the joints, or use a terminal block with an additional layer of insulating sheet, with decent overlap, underneath it.

It sounds as if you got a very good deal if you went back for the other transformers. They look useful and clearly marked. Make sure you parallel the primaries again for proper operation.

If unsure of anything, post photos as you go.
Gyro:

--- Quote from: 001 on December 11, 2018, 11:09:16 am ---
--- Quote from: Hero999 on December 11, 2018, 10:33:25 am ---Why not use a toroidal construction for a medical grade isolation transformer?

There's an earthed screen between the primary and secondary, which both offers additional protection and prevents capacitive coupling between he secondary and primary windings.

--- End quote ---

Yea

And it adds capasitance between sec and ground so still shock hazadrd

--- End quote ---

Although if it is a medical grade one, steps (insulation thickness etc.) will have been taken to minimize capacitance - there are maximum specs for these things! It is a reputable brand - there is no shock hazzard.
001:

--- Quote from: Gyro on December 11, 2018, 11:20:59 am ---
--- Quote from: 001 on December 11, 2018, 11:09:16 am ---
--- Quote from: Hero999 on December 11, 2018, 10:33:25 am ---Why not use a toroidal construction for a medical grade isolation transformer?

There's an earthed screen between the primary and secondary, which both offers additional protection and prevents capacitive coupling between he secondary and primary windings.

--- End quote ---

Yea

And it adds capasitance between sec and ground so still shock hazadrd

--- End quote ---

Although if it is a medical grade one, steps (insulation thickness etc.) will have been taken to minimize capacitance - there are maximum specs for these things! It is a reputable brand - there is no shock hazzard.

--- End quote ---


But what capasitance value is ok?
Gyro:
All covered (all approvals and specs) in the web page already quoted if you bother to look.. https://www.plitron.com/default-factory-specs/medical-grade-toroidal-transformers/.

For the OP's 300VA model, capacitance is less than 0.78nF, Leakage current less than 13uA. Below the threshold of human perception. As I said before NO shock hazard.
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