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Old 14th October 2012, 08:31 AM   #11
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Ok. my plan is for 16A continous through the supply at 34 V single rail supply. Its a 600VA toroid with 10x10000uF capacitors.
can i use CRC , my plan is to keep the current 40000uF as first C then add R and then another C what could be the values of R and C ??? any guidance or thumb rule?
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Old 14th October 2012, 08:37 AM   #12
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The transformer will overheat asked to produce that much (544W) continuously as the power factor of those caps will mean 600VA is easily exceeded.
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Old 14th October 2012, 09:32 AM   #13
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I think you are referrring to the input transformer. sorry for typo 16A is the Ac current i would be ruuning at 4A per side thats 8A total. I hope that ruuning at continous half the power would be ok then. i.e. 32x8=256W and the tranformers is of an amplifier with 500w class B amplifier. any comments on its?
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Old 14th October 2012, 01:21 PM   #14
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oh did i mention that no speaker coupling capacitor was used :-)
some plans improvement.....using the secondary coil of out put transformer as CLC filter.
recifier diode noise cancellation with ceramic capacitors.
EMI filter for mains.
replacing the three 0.22uf electrolytic coupling capacitors with high quality metal film around 2.2 uF.
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Old 15th October 2012, 05:33 AM   #15
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Go to the ESP site. There, u can find a psu circuit known as capacitance multiplier. May be, it will solve your hum problem.

I would first confirm the hum is sourced from the psu itself as there r other sources of hum like leakage from a transformer.

Gajanan Phadte
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Old 15th October 2012, 10:53 AM   #16
DF96 is offline DF96  England
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Quote:
Originally Posted by sreten
(One of the answers in this thread is simply wrong .....)
(One of the answers in this thread is very misleading .....)
Very helpful reply to us all.

As I said, the toriodal transformer could be used as a commmon-mode choke, which I think answers one of the OP's questions. Perhaps I should have added that a common-mode choke is not what is needed for PSU smoothing.
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Old 15th October 2012, 08:09 PM   #17
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DF96: I am not good at explaining and English is not my native language. Could you please explain to the OP the difference between magnetizing current and load current. How load current is compensated by primary current and magn. current is not. I think he has problems understanding why a transformer with a high sec. current rating can be saturated by a very low current, be it AC or DC, that is "forced" through its secondary.
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Old 15th October 2012, 08:47 PM   #18
DF96 is offline DF96  England
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OK. In a transformer the magnetic flux generated by the primary current is largely cancelled by opposite flux generated by secondary current. This means that the core only sees a much smaller net flux. Using a transformer winding as a choke means there is no cancellation, so maybe only 5-10% of current rating is possible.

A common-mode choke achieves flux cancellation by sending the same DC current through two windings in opposite directions. The core only sees flux generated by the difference between the two currents. Note that another (RF) name for a common-mode (CM) choke is a current-mode balun.

PSU smoothing needs an ordinary choke, not a CM choke.
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Old 22nd November 2012, 11:20 AM   #19
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If anyone is still interested the use of a toroidal transformer as a common mode choke can work very well . I did try the leap to a ferro-resonant idea . That is where one of the two coils is connected in shunt to a capacitor . Fascinating and everything got rather hot , it did start to work it should be said . The capacitors from memory were in the many 10's of uF . If anyone succeeded in this I would be more than very interested . Oneac UK had devices that claimed 1% THD in the past ( 50 Hz ) . CVT's may not work well with class B amplifiers ( D ) . I am told by the man who makes my transformers that CVT's are a black art to design . He was trained by the ex chief engineer of Partridge so is fairly reliable when saying this . 8KVA he does at the drop of a hat .

Voltage regulation : TRANSFORMERS
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Old 22nd November 2012, 04:07 PM   #20
jcx is online now jcx  United States
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DC current rated chokes may have air gaps where you can't easily see them in the finished product - under the bobbins/windings - so they only superficially appear to be built the same as transformers


reducing hum doesn't always require super low supply ripple - you could use a topology that has good supply rejection - just about any circuit except OTL low mu Triode

at your stated V you must be using SS which usually have high output conductance/low internal V feedback (it is high internal V feedback that gives triodes low mu) - should be able to have good supply rejection

Last edited by jcx; 22nd November 2012 at 04:13 PM.
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