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Old 22nd June 2004, 11:12 PM   #1
PetarLD is offline PetarLD  Bulgaria
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Question Dangers in connecting transformer secondaries.

Hi guys, its summer and I have some free time to enhance my amplifier.

So here I go: First I have a P3A, the transformer that I used has 7 secondaries as drawn in the picture ( I don't have any schematitcs for this transformer so I had to draw my own) I want to connect the two 9.4VAC so I can add the voltage to the 17.1 VAC secondaries and that would give me around 26 VAC and my question is, are there anything that I should consider any dangers, any special way that I have to connect it, because I think that if I connect it backwards or something the voltage would actually cancel and drop so I was wondering if that would destroy the transformer?

Currently I have my amp connected to the 17.1 VAC secondaries and that only gives me 24VDC (Not Enough )

Thanks, I can't wait for your answer.

Petar
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Old 23rd June 2004, 12:04 AM   #2
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Shouldn't be a problem, as long as you connect windings in series. The worst that can happen is you'll subtract voltages rather than add, depending on relative polarity.

Rune
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Old 23rd June 2004, 01:17 AM   #3
PetarLD is offline PetarLD  Bulgaria
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Quote:
Shouldn't be a problem, as long as you connect windings in series. The worst that can happen is you'll subtract voltages rather than add, depending on relative polarity. Rune
Thanks, but I have one more problem, my capacitors are rated 35V 4700uF by my calculations, the voltage is going to be 36V is that a big problem?

Thanks,

Petar
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Old 23rd June 2004, 01:25 AM   #4
imix500 is offline imix500  United States
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Yeah... upgrading those to a 47v rating or so would be a good idea. Unless you want to possibly hear what a capacitor rupturing sounds like. And your voltage could easily be slightly higher than 36v unloaded, so yes replace them.
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Old 23rd June 2004, 01:29 AM   #5
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Default I also think no problems, but,.....

If one of those windings uses a thin wire, you will have problems related to power.....more voltage, and resultant power not good.

Best way, is the stone age way.... do it and put a low value resistor...measure voltage on it, and current througth it....multiply and you will see the power you can have....lets see, as an example:

If you used 10 ohms resistor, and measured voltage on it was 25 volts... current will be 2.5 amperes, the power, in this case, 62,5 watts.... this way, if you put some regulator to use only 12 volts, probably the current will reach 5A..... take a look that 5A multiplied by 12 volts resulted in 60 watts, alike the first test.

Also, if the open circuited voltage measured was high, lets see 50 volts, you will can drain a little bit more than 1 ampere to keep avoid this voltage be too much reduced....because multiplied 50 by 1A, result is 50 watts.... 20 percent less than maximum... voltage will not reduce too much.

This is not precise, just one idea, using old ohm law, can make you evaluate with big errors, but will allowed you to have sure....good!, or no good!, to the use you need.

If all coils wires same diameter... wonderfull!...but not common, this way some of them more power than the others, and if difference to great.... can burn the one that is too much delicated to be crossed with 5 amperes current.

This is a simplified method to have one idea, not a PHD thesis.

Carlos
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Old 23rd June 2004, 01:57 AM   #6
Eva is offline Eva  Spain
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Applying overvoltage to capacitors is like a game. Sometimes you win and sometimes you lose. Play it with care

You can apply overvoltage to some capacitors for some time but you can't apply overvoltage to all capacitors all the time
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Old 23rd June 2004, 04:26 AM   #7
PetarLD is offline PetarLD  Bulgaria
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Hey guys, thanks for the answers, I was so excited that I was gonna have more powerful amplifier and then destroyer X came along, I thank him a lot for saving me time and trouble. As he said,
Quote:
If one of those windings uses a thin wire, you will have problems related to power.....more voltage, and resultant power not good.
And that's exactly what happened, I pealed off the paper on top of the soldered windings, and the wires from the 9.4 VAC windings were half as wide as the 17.1 VAC windings, so that might have resulted in pretty badly melted transformer, or causing the winding to heat up a lot during use. I don't think its worth it.

Petar
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Old 23rd June 2004, 05:08 AM   #8
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destroyer X is absolutely right about wire size mismatch problems. As well, you can sometimes exceed maximum voltage ratings on transformers by series connecting secondaries.

Do the right thing. Get a proper transformer and capacitors!

Take care,
Doug
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Old 24th June 2004, 03:37 AM   #9
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Default I feel always very happy when i can help

But, have sure, reading her i understood that Eva is the best in this part of electrical, magnetic fields and transformer.... she may be better other fields....but, reading all forum, i could see no one can beat her in this matter.
She do not like to appear, this way, you may feel happy with her presence.

Carlos
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