Isolation Transformer

I would like to Make a isolation transformer for using in testing switch mode power supplies.
What size transformer's would you use and why.

Gregory said:

I would like to Make a isolation transformer for using in testing switch mode power supplies.
What size transformer's would you use and why.

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You need an isolation transformer larger than the power you want to draw from it, so if your SMPSU is 400W, use a 500W transformer.

And why? Most of case You need to measuring with scope on primary side, and the scope is internally grounded, to avoid elecric shock...

DON'T FLOAT THE SCOPE!!
People have been killed........

spuffock said:

DON'T FLOAT THE SCOPE!!
People have been killed........

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It's not an argument to get into again (it's been done to death too many times before), but an earthed scope can be more dangerous than an unearthed one - depending on the circumstances.

As long as you are totally aware of what you are doing, and what is earthed and what isn't, neither method is more dangerous than the other, both are potentially dangerous under certain circumstances.

It's extremely common practice in service departments not to have scopes earthed (this also applies to huge worldwide electronics companies!) - personally I consider an earthed scope too dangerous for normal use - but I repeat! - EITHER EARTHED OR NOT, YOU MUST KNOW WHAT YOU ARE DOING!.