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Safety. on grounding a balanced trafo.
Safety. on grounding a balanced trafo.
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Old 16th September 2019, 04:22 PM   #1
phi112358 is offline phi112358
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Default Safety. on grounding a balanced trafo.

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!

Last edited by phi112358; 16th September 2019 at 04:24 PM.
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Old 16th September 2019, 04:41 PM   #2
Mark Whitney is offline Mark Whitney  Netherlands
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Never connect N to the chassis! Treat it as of it is live.
From the mains you only connect PE to the chassis.
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Old 16th September 2019, 04:52 PM   #3
rayma is online now rayma  United States
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Quote:
Originally Posted by Mark Whitney View Post
Never connect N to the chassis! Treat it as of it is live.
From the mains you only connect PE to the chassis.
+++++++++1000
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Old 16th September 2019, 05:04 PM   #4
DF96 is offline DF96  England
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A metal case but no ground means double insulation is necessary for safety.
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Old 16th September 2019, 05:31 PM   #5
sq225917 is offline sq225917  United Kingdom
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Send a message via MSN to sq225917 Safety. on grounding a balanced trafo.
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.
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Old 16th September 2019, 06:15 PM   #6
JMFahey is offline JMFahey  Argentina
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And in any case a "trafo" never has
Quote:
6v+, 0 6v-
outputs.

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

If itīs 2 wire mains itīs 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.
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Old 19th September 2019, 08:21 AM   #7
phi112358 is offline phi112358
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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.
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Old 19th September 2019, 08:25 AM   #8
phi112358 is offline phi112358
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Default Ahh,makes sense

Quote:
Originally Posted by sq225917 View Post
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.
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Old 19th September 2019, 08:38 AM   #9
phi112358 is offline phi112358
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Quote:
Originally Posted by JMFahey View Post
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 itīs 2 wire mains itīs 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.

Last edited by phi112358; 19th September 2019 at 08:59 AM.
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Old 19th September 2019, 08:32 PM   #10
TBTL is offline TBTL  Germany
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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.
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