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Building a isolation transformer...

Hi,

I've got an old tripplite power conditioner box and while it may be an isolation transformer of some sort, I am not exactly sure what it is so I am going to rewire it so I know for sure. I have a isolation transformer or I could possibly use the transfer in the conditioner box.

My question is:

What do you do with the ground? The primary ground comes in and is connected to the chassis.

The secondary winding will become the outlet's hot and neutral.

What about the outlet's ground?

If you leave it open, it isn't a ground.

If you connect it to the line ground, then it is a ground, but really will it function as one considering that the hot/neutral are isolated (if there is a fault)?

If you connect it to the line ground and also connect it to the secondary windings neutral (bonding the secondary winding neutral to line ground), then is it truly isolated?

What do commercial units do?

I'm planning on using this for hobbiest type use...

Thanks,

Alan

Reply to
Default User
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"Default User"

** They carry the supply ground wire through to the outlet socket - for obvious safety reasons.

It is *characteristic* of all AC supply isolation transformers that connection either of the secondary wires to safety ground will blow no fuse nor trip any protection devices.

Such transformers should be used only when it is necessary to make bench tests and measurements on live, non-isolated line voltage devices.

Then put it away.

..... Phil

Reply to
Phil Allison

Hi Phil,

So you are saying I should carry the ground from the input line cord to the chassis and to the output receptacle ground as well? But, leave both the secondary outputs hot and neutral unbonded?

Wouldn't it be better if I just used a 2 conductor receptacle with no ground? I mean is it really a real ground since neither the hot nor neutral coming off the secondary can deliver any current to it?

Thanks

Alan

Reply to
Default User

"Default User"

** They carry the supply ground wire through to the outlet socket - for obvious safety reasons.

It is *characteristic* of all AC supply isolation transformers that connection either of the secondary wires to safety ground will blow no fuse nor trip any protection devices.

Such transformers should be used only when it is necessary to make bench tests and measurements on live, non-isolated line voltage devices.

Then put it away.

** Yep.

** It still functions perfectly as a safety ground, since nothing ( like some chassis) connected to it can become live.

What the hell do you think a protective ground conductor is for ??

And NEVER delete ALL the prior posting

- like you just did.

..... Phil

Reply to
Phil Allison

the last two isolating transformers I inspected closely had 2 conductor line cords cast into the potting compound.

the boilerplate on the one I have now says "NZSS1379 Class 2" but I don't know what that means.

this is an old 1300VA transformer for power tools, It dates from before ELCB type protection

bye.

Reply to
Jasen Betts

Commercial units can be called isolation transformers and the ground goes straight through and one leg of the output is tied to ground forming a new neutral. This gets rid of common mode noise to ground. I think many times you have to isolate ground and any connections to the secondary, for test purposes. There can be at least two scenarios. Its either noise control or true isolation. Got to be carefull. All tripplite isolations tranformers have the ground tied to secondary as per NEC.

greg

Reply to
GregS

Try an Internet search on "grounding separately derived systems" (without the quotes).

Reply to
JosephKK

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