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Old 8th September 2013, 10:50 PM   #1
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Default Newbie asking about transformer

I have a big toroidal transformer whose secondary voltages are 90v-45v-0-45v-90v.
Can I use a 90V-45V-45V-0-90V transformer for only a 45V secondary windings?

Transformer power is 1460VA, but how much power I can get out if only 45volt secondary is using? 90v secondaries would not be connected.

Or ..

Can I use connection of this picture? All rectifiers should be 90V ac voltage, in which case I can use all the secondaries of the transformer.

......ABANDONED version......

After rectifying the voltage should be +-65Vdc

Sorry my bad english... Google translator.

Last edited by TurvenuijaFIN; 9th September 2013 at 08:45 PM.
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Old 9th September 2013, 11:13 AM   #2
DF96 is offline DF96  England
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No you can't use the connections in your diagram.

How much you can get from the 45-0-45 depends on how the transformer is wound, but expect about half the VA rating. This is because you can probably draw about the same current, but at only half the voltage.
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Old 9th September 2013, 01:44 PM   #3
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This circuit is a time bomb.
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Old 9th September 2013, 02:05 PM   #4
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NO - NO - NO

The only way that you can get +/- 65V is to use the 45V taps and the centre tap.

The 90V windings would have to remain unused.

If you were to use both halves of the transformer for two completely isolated amplifiers they would be dangerous as the 0V in each amp would have a potential difference of 130V. Anyone touching both cases simultaneously would receive a severe shock OR WORSE.
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Old 9th September 2013, 02:19 PM   #5
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Ok.

Forget that.

The transformer should be out of the half of its power using a 45v secondaries.
Transformer are from T-amp TA2400.

I think I'll buy directly from a suitable transformer for ucd400's
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Old 9th September 2013, 04:55 PM   #6
hongrn is offline hongrn  United States
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Good tutorial right here on transformers:

Building a Gainclone chip amp power supply.
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Old 9th September 2013, 08:40 PM   #7
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Solved the problem. I opened the transformer windings insulation check the wire flow.

45v and 90v coil is the same continuous wire and are connected in series.
I cut wire after 45v outlet and then plug the disconnected end of the zero potential.

Now i have four outlet. 45V-45V-0-45V-45V
And now I can connect the outputs together and I can get a more powerfull 45V-0-45V outputs.
a voltage difference between the outputs of only 0.1V

Click the image to open in full size.


Original wiring.
Click the image to open in full size.


Modified wiring
Click the image to open in full size.
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Old 9th September 2013, 09:10 PM   #8
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by TurvenuijaFIN View Post
45v and 90v coil is the same continuous wire and are connected in series.
I cut wire after 45v outlet and then plug the disconnected end of the zero potential.

Now i have four outlet. 45V-45V-0-45V-45V
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Old 10th September 2013, 09:42 PM   #9
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New secondary outputs.
Paraller connected 2X 45v-45v-0-45v-45v secondary windings. Now I have 2X 45v-0-45v 700VA outputs.

Click the image to open in full size.

Click the image to open in full size.

Output voltage is steady 48.3V on all outputs (235V primary voltage) Without load.

Not so sweet, but it works.

Last edited by TurvenuijaFIN; 10th September 2013 at 10:02 PM.
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Old 13th September 2013, 03:05 PM   #10
AndrewT is offline AndrewT  Scotland
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Check your primary current with the secondaries wired as you have them.

Then wire up the rectifier, but not the smoothing caps and re-check the primary current.
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