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Old 05-19-2019, 02:14 AM   #1
llonen
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Default Isolation transformer

Firstly I feel this is something I should already know the answer to but it eludes me. Anyways I have been in the repair business for some 15 years or longer and I still don't have an isolation transformer yeah (bad me). So I starts looking at options for 2-3kw isolation transformers and and the price is a little more than I would like to pay out.

So I gets thinking I have a number of 230v/110 CTE step-down isolation transformers for working on power tools which I also get in for repair from time to time. They are around 3kva rating is there any reason I can't connect two of these back to back to make a 1:1 isolation transformer.
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Old 05-19-2019, 05:17 AM   #2
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Default Re: Isolation transformer

Assuming they are in fact real transformers, then sure.

Just make sure it's not actually an autotransformer - some of those step-down ones are. And those won't give you any isolation at all!
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Old 05-19-2019, 08:51 AM   #3
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Default Re: Isolation transformer

I found plenty isolation transformers in a regional ham flea market. I've got one, but hardly use it. I guess that depends on what one repairs.
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Old 05-19-2019, 11:09 AM   #4
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Default Re: Isolation transformer

To be honest its not something I have ever felt the need to setup, it might be useful for scoping smps I suppose but I have a battery scope for that furthermore most of them are such cookie cutter designs the need to scope out stuff on them is largely irrelevant to me.

I will have a go at setting this up but I am certainly not paying the going prices for 2-3 kva isoloation transformers. So its a couple of 230/110 cte transformers then, I might need to obtain one more since two are in regular use and one is used for testing 110 volt tools which leaves one spare. I will let you know how I get on.
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Old 05-19-2019, 05:51 PM   #5
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Default Re: Isolation transformer

Quote:
Originally Posted by llonen View Post
It might be useful for scoping smps I suppose but I have a battery scope for that
True, that will prevent you from shorting something to ground, but it will not protect you from a direct mains connection.

Using the isolation for the DUT, with a battery scope or not, will be a bit safer.
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Old 05-19-2019, 05:53 PM   #6
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Default Re: Isolation transformer

Quote:
Originally Posted by agent24 View Post
true, that will prevent you from shorting something to ground, but it will not protect you from a direct mains connection.

Using the isolation for the dut, with a battery scope or not, will be a bit safer.
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Old 05-19-2019, 06:15 PM   #7
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Default Re: Isolation transformer

be careful using 2 yellow bricks like that .

Last edited by petehall347; 05-19-2019 at 06:20 PM..
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Old 05-19-2019, 10:03 PM   #8
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Default Re: Isolation transformer

Quote:
Originally Posted by llonen View Post
To be honest its not something I have ever felt the need to setup, it might be useful for scoping smps I suppose but I have a battery scope for that furthermore most of them are such cookie cutter designs the need to scope out stuff on them is largely irrelevant to me.

I will have a go at setting this up but I am certainly not paying the going prices for 2-3 kva isoloation transformers. So its a couple of 230/110 cte transformers then, I might need to obtain one more since two are in regular use and one is used for testing 110 volt tools which leaves one spare. I will let you know how I get on.
I would verify that they are not Auto-Transformer, you can easily verify by checking the resistance between the windings.
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Old 05-20-2019, 02:05 AM   #9
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Default Re: Isolation transformer

Already checked on the one spare now looking for another
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