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Repurposed Industrial Control Trans With Many CT Sections
Repurposed Industrial Control Trans With Many CT Sections
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Old 13th October 2018, 05:13 PM   #1
erix is offline erix  United States
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Default Repurposed Industrial Control Trans With Many CT Sections

Howdy Folks,

I searched for this but couldnít find an answer for what Iím thinking of doing.

Iíve got a couple of 4lb transformers from some Japanese industrial robots from the early 80ís. Iíd like to use them for something but it will take a bit of finaglling as they have a lot of sections There is a 100V primary, one 10-0-10 secondary labeled 0.1A and SIX 10-0-10 secondaries, each labeled 0.2A. None of the CTs are connected internally.

I have a scope and can determine the phase of the individual sections however Iím stumped as to which way to connect them. I want to make a bipolar supply with as much current as I can get. For the purposes of this discussion Iíll only use the 0.2A sections. Should I tie all the + phases together, the CTs, and the - phases and then rectify the combined + to CT and - to CT to make a ~ +/-17V? Will that be 1.2A?

Or should I rectify each section and parallel the resulting DC outputs?

Thanks for any advice you can offer!
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Old 13th October 2018, 05:41 PM   #2
Michael Bean is offline Michael Bean  United States
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Are you planning to run it on 120 VAC? Mains voltage can rise to 132 VAC and still be within specs, that would be 32% over the voltage rating of the transformer, definitely a cause for concern. Further, unless that particular transformer is rated for paralleling the secondaries, I wouldn't do that, it very well could cause the transformer to over heat. And even if all of that is OK, no you won't be able to draw that much current. That transformer is rated at about 26 VA, so with the over voltage on the primary, you'll need to de-rate the secondary current to keep the transformer within it's power rating, Probably about 850 mA tops.

Mike
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Old 13th October 2018, 09:42 PM   #3
erix is offline erix  United States
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Thanks for the great advice Mike. I was about to just plug it in and see what happens but my gut made me pause and ask the question and now I’m glad I did! Looks like I have some new doorstops!

Thanks again!

Go Vikes!
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Old 13th October 2018, 10:57 PM   #4
PRR is offline PRR  United States
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Quote:
Originally Posted by erix View Post
....transformers from some Japanese industrial robots ...
They are taking over.

Quote:
Originally Posted by erix View Post
Will that be 1.2A?
No. DC current out is always less than AC current from PT. Factor is 1.6 to 1.8. You can take 0.7A of DC out (at +/-13VDC).

Quote:
Originally Posted by erix View Post
a 100V primary, one 10-0-10 secondary labeled 0.1A and SIX 10-0-10 secondaries, each labeled 0.2A. ...
Six 20V 0.2A is six*4VA or 24VA. Not a heap of power.

100V would be a smoke-bomb on US/Can 120V power. However the seventh winding, 20V, can be put in series with the 100V winding to make a 120V winding. You MUST get the polarity right!! Assuming 24VA total load, ah, bad-- the primary current is 0.2A and you only have a 0.1A winding. I figure perhaps 50:50 odds it would "work for months", it won't burn-up right away, just run hot in the one winding; and being a small fraction of the total copper "maybe" the heat won't be bad. But me, I would not try this at home. (Maybe in the garage.)
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Old 14th October 2018, 12:06 AM   #5
Michael Bean is offline Michael Bean  United States
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Quote:
Originally Posted by erix View Post
Thanks for the great advice Mike. I was about to just plug it in and see what happens but my gut made me pause and ask the question and now I’m glad I did! Looks like I have some new doorstops!

Thanks again!

Go Vikes!
It's going to be a little chilly for the Cardinal's fans...and the temperature will be unseasonably cold too!
I hope the Vikes don't play down to the competition again.

Mike
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Old 14th October 2018, 12:45 AM   #6
AllenB is online now AllenB  Australia
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Quote:
Originally Posted by erix View Post
Looks like I have some new doorstops!
Marginal limitations, at least. Tying the windings in parallel does seem tempting. If it were me I would compare each for Voltage and resistance, not that this will tell you everything, and maybe begin with very small current sharing resistors.
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