Safety. on grounding a balanced trafo.

[phi112358]

Trafo has 2 inputs and 3 outputs. Case is steel.
Outputs: +6v, -6v, and neutral. It is balanced.

Trafo will connect to an a regulator.

My options I have comeup with:

1. Connect ground (N wire from mains) to enclosure
2. Connect 0v output from balanced trafo to enclosure
3. Shield the 0v trafo output wire from enclosure

• the trafo is 6v+, 0 6v- outout. 1A curent max
• 2 wire input (N and live)

How do I make the thing safe?
I know which is N and which is live for 220v mains input


The case is covered in nonconductive paint but has shielding connections on the inside.


I need a person knoledgable about balanced trafos to answer this question.


I have a fewmore questions but will be grateful to anyone who can answer the questions above or provide a simple explaination about how to make this work.


Thanks,


Movin on up!

 

[Mark Whitney]

Never connect N to the chassis! Treat it as of it is live.
From the mains you only connect PE to the chassis.

 

[rayma]

Never connect N to the chassis! Treat it as of it is live.
From the mains you only connect PE to the chassis.

+++++++++1000

 

[DF96]

A metal case but no ground means double insulation is necessary for safety.

 

[sq225917]

3 pin iec socket, wire L and N to traffo, wire gnd from ice socket to electrically conductive point on chassis.

Sounds like a 0v centertap transformer rather than a balanced unit which is typically a 1:1 ratio unit.

 

[JMFahey]

And in any case a "trafo" never has

6v+, 0 6v-

outputs.

It either has 6VAC+6VAC or 12VAC center tapper or it is not a "trafo" but a Power Supply.

If it´s 2 wire mains it´s either very old when that was the norm or very modern, double insulated, where it does not actually *need* a third Ground wire.

Clearly describe which of these applies, because it is VERY important and changes suggestions considerably.

State brand and model and if possible add a picture.

 

[phi112358]

I had a suspicion about that, connecting the neutral output to the case. There are 2 wires going in and 3 coming out. It is an E and L henry trafo from thailand. So Luckilyy my new apartment has ground wires on the mains along with live and neutral.Will utilize that ground wire. Should Ijust put electrical tape over the live part of the 0v wire coming out? (there are 3 wires coming out, both +6V & -6V, then sero. Seeems I should just cover the zero output wire in electricaltapefrom allthe advice I(think) I interpreted correctly.

 

[phi112358]

Ahh,makes sense

3 pin iec socket, wire L and N to traffo, wire gnd from ice socket to electrically conductive point on chassis.

Sounds like a 0v centertap transformer rather than a balanced unit which is typically a 1:1 ratio unit.

yes it is a 0v centertap trafo.
Must be.

 

[phi112358]

And in any case a "trafo" never has outputs.

It either has 6VAC+6VAC or 12VAC center tapper or it is not a "trafo" but a Power Supply.

If it´s 2 wire mains it´s either very old when that was the norm or very modern, double insulated, where it does not actually *need* a third Ground wire.

Clearly describe which of these applies, because it is VERY important and changes suggestions considerably.

It is an E and l Henry trafo and it is wound so the middle of the secondary comes out as one of the 3 secondary wires (or more specifically the V of the center tap of the secondary comes out as halfway between the V of the two outer secondary terminals. One of the three secondary outputs is actually just the center of the wire which forms the secondary side of the trafo. I have taken one apart before to check out how it was constructed . Primary has only 2 inputs. connect the AC meter from center wire to either of the two other secondary outputs and it reads 6v. Yes it is AC so there really isn't a + and a- but if you connect the meter between both outer wires, it reads something like 12v. I have used these for years, surely unloaded it reads a bit higher. That is the gist of the unit


It is not a normal shaped trafo.The primart and secondary each occupy one seperate half of the trafo. It is not wound in layers but in discrete halves.



State brand and model and if possible add a picture.

 

[TBTL]

Do the specifications of the transformer explicitly mention 'double insulated' or 'Class II'? If not, assume that it isn't, so the metal case must be connected to safety ground.

 

[JMFahey]

Not to take it lightly and disregard safety, but in principle winding on separate bobbin halves goes a long way towards better insulating them.

Safer than winding primary and secondary one on the other and relying on mylar sheet to separate them.

 

[phi112358]

Not to take it lightly and disregard safety, but in principle winding on separate bobbin halves goes a long way towards better insulating them.

Safer than winding primary and secondary one on the other and relying on mylar sheet to separate them.

Very smart. Argentina? wow man. Guess C-core would be the best way to go for that.


I might need help on some OTs. Maybe I can ask you some questions. I will sendyou a friend request but of course we should discuss it all in public for the bnefit if others and this site.