Power transformers versus amplifier output power..what is your option? - Page 2 - diyAudio
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Old 7th May 2009, 10:05 AM   #11
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Default You gave me another idea to think about Pavel


If we decide a high iddle current..some class A or increased bias Class AB, them the transformer voltage will go down...it is another option, to use the supply always loaded by a class A amplifier to reduce output voltage...this will ask lower insulating voltage to the filter condensers..avoiding the ones to 80 volts...those ones are very expensive here.

Ahahahah... the amplifier fuse cannot blow...because if blows the supply unloaded will have voltage increase to 80 plus 80 volts..and my economic lower voltage (loaded voltage) electrolitic condenser will explode!...ahahahaha..seems very dangerous too.

As we see, there are many decisions, and some of them are dangerous, other are expensive...the best idea must be selected.

Young folks, novice, beginners and students will be happy with this thread.

Increasing the current into the amplifier, then the amplifier will work alike a parallel voltage regulator, a shunt that gonna load the supply and reduce the supply voltage.

It is interesting, but the amplifier cannot have fuses... seems the electrolitic condenser capacitance needs will increase too...starting with 1 ampere, for instance, will need enormous condenser bank to keep ripple under control.

I am thinking the best way to use the transformer...as you see..one solution uses high voltage...expensive condensers..other option uses lower voltage..but condenser capacitance will need increasing..so... the best solution is not to use this transformer, this is what seems to me, because it is creating problems as consequence of bad voltage regulation..low power unit.

I have another one.... a strong one that produces 45 volts and the voltage will not go bellow 40 volts even loaded with 400 watts..this may be a good option.

The thread has two functions...one to help me to decide the better way to use the big transformer... even to decide not to use it, and if decided to use it, if will be used only rectified and filtered or be using electronic regulators.

Other function is to allow young novice diyers to learn some tips and tricks, the analisis and testings we need to make when we remove transformers from dismounted old amplifiers and start to decide how to use them.

Many folks, novice, use to come to me to learn basic electronics...some practical things... daily problems alike transformer wires, grounding and so on... those boys will be happy with this thread.

regards,

Carlos
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Old 7th May 2009, 12:05 PM   #12
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Even with ideal transformer we get high ripple for 1A, like this for 10 000 uF caps. To lower the ripple, the only way is to increase capacitance.
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Old 7th May 2009, 12:48 PM   #13
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It doesn't look like that transformer is even near big enough for what you are asking it to deliver. At a reasonable overload, drop to 60V might be expected: 9A DC per rail with 7 ohms. This will need about 16A RMS from both ends of the transformer (bad power factor of rectifier). At 2x55V nominal that would be almost a 2000VA load!


Best indicator is probably size. How big and how heavy is it? Looks like somewhere around 200-400VA to me, but hard to judge from the picture.

Maybe it's useful for your single supply amp? Use the standard two-diode full wave connection.
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Old 7th May 2009, 12:49 PM   #14
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While no transformer is ideal (like simulation) , some are better than others. Used to think the world was only EI trafo's ,
got a hold of some toriods.... what a difference.

Almost no heat , much less voltage drop up to trafo rating , and less ripple with the same rectification/capacitance.
I still have a few EI's , but will use them for my less demanding applications (testing , kids amps , etc.).

No wonder they are the preferred equiptment for both audio and industrial applications.
OS
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Old 7th May 2009, 01:09 PM   #15
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Default I will inform transformer size latter..but will do that..for sure


Yes...i have a toroidal one too...they are better.

But i think i gonna use this one..... the transformer was coiled, wounded by myself, a hard manual work to do.... has many outputs that results 35 plus 35, 45 plus 45, 55 plus 50 and 65 plus 65 after rectification and filtering...those are DC voltages.

And power is reasonable.... something near 500 watts.

The transformed iron came from an AC voltage stabilizer , a step down unit we use here to computers...from 220 to 110 volts and 1000 watts (they say..but really is something alike 500 watts)

I am studying boards positioning... filters are 35.000uf plus 35.000uf

regards,

Carlos
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Old 7th May 2009, 04:17 PM   #16
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Default Transformer width


attached,

regards,

Carlos
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Old 7th May 2009, 04:20 PM   #17
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Default Transformer Heigth


This transformer, when original (now a days a result of refurbishment) was installed into a Technics Receiver...the back panel had 500 watts of power consumption...so..originally, maybe a 450 watts transformer.

Was made once again... a lot of other coils, with other voltages, where removed... this way the wire thickness could be increased...i have measured around 600 watts as posted into the first or second posting in this same thread.

regards,

Carlos
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Old 7th May 2009, 04:23 PM   #18
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Default Transformer length


When we load a transformer, using low value resistance, you can have the information about the real power.

If size or calculations inform different value, i will always trust the real load testing.

regards,

Carlos
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Old 7th May 2009, 04:34 PM   #19
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Okay, looks like it's the same size as a 500VA transformer I have here. The power rating of the transformer is how much it can deliver without meltdown. 600W for a short while doesn't seem unreasonable at all, but the continuous maximum power without overheating will be something like 300W total due to the ~0.7 power factor of the rectifier.

If you want to load test the transformer you need to leave it with the test load for at least 30-60 minutes. Transformers take a long time to heat up...
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Old 7th May 2009, 04:42 PM   #20
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Default Uops!...yeah!>..you are rigth...i have forgotten that!


Will produce more testing next week as i am busy with other things.

Thank you....yes!>... heat!

regards,

Carlos
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