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Ultra high current DC blocker
Ultra high current DC blocker
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Old 4th January 2020, 06:37 PM   #1
montana is offline montana  Israel
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Default Ultra high current DC blocker

Hi guys
Thanks for everyone who comments here.
I wish to built DC blocker and AC filter for my system.
I have dedicated 35A line that feeds all the system
The system consist of 2 monoblocks of mark Levinson 33H
And of course there is preamp dac and audiophile PC with linear power supply the loudspeakers are very demanding Wilson audio Alexandria XLF.
Mark Levinson recommend to use 30A line for each amp when use in USA 115v 60Hz since I am living in 230v 50Hz area I understand that I need half of the current for each line..
Unfortunately Mark Levinson don't mention power consumption for each amp all I know is that each amp uses 20A main fuse and has idle of 540W ever more each amp uses 3.5KVA transformer.
I have looked at few DC blocker schematics and I saw that most of the design installed on the hot wire and other design installed both hot and natural as well...
Is there any advantages of using both and making it symmetrical ?
I don't know what are the capacitance value that I need ?
How much ripple current I need to feed this 35A line ?
And what voltage rate of capacitors ?
Ever more is there any advantages to use ultra fast and soft recovery diodes in a DC blocker ?
I tried to measure with my fluke 289 and get reading of -150mV DC between natural and ground wires which indicates that the DC current flows from the ground to the natural wire.
I understand that this is one of the problems with the electric company that they connects the natural wire of the transformer to the ground bus bar.

Thank you all
God bless you
Attached Images
File Type: png DCB_Power.png (52.3 KB, 252 views)
File Type: gif xfmr-dc-blocking-simpl.gif (5.4 KB, 250 views)
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Old 4th January 2020, 06:56 PM   #2
Mooly is offline Mooly  United Kingdom
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Ultra high current DC blocker
Have a read at this which shows a final worked design in figure 8:
Mains DC and Transformers
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Old 4th January 2020, 07:00 PM   #3
montana is offline montana  Israel
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Thank you Molly
I have red this half of it I didn't understand
Ever more questions like advantages of using at the natural wire as well I didn't saw...
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Old 4th January 2020, 07:25 PM   #4
sq225917 is offline sq225917  United Kingdom
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Just buy a sjostrom DC blocker, the bigger model from Per Anders. Works perfectly on big amps.
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Old 4th January 2020, 07:28 PM   #5
montana is offline montana  Israel
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I know that is always easy to plug and play ��
But still I wish to understand why most of the designs do not use the natural wire as well ??
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Old 5th January 2020, 12:52 AM   #6
trobbins is offline trobbins  Australia
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In a TNS type mains system, any switch or fuse component must be in the active line - there should be no switched part in the neutral. If something goes wrong with the DC blocker circuitry, it is 'safer' for it to be in the active lead, not the neutral lead.

There are no advantages, and only a disadvantage (the safety aspect above) in making it a symmetrical arrangement with active/neutral lines.

Rod's article identifies the general sizing of the ripple current rating of the 'capacitor' - it is the max anticipated current of your load equipment. If each equipment has a 3.5kVA transformer, then size the ripple current requirement for that.

There is no effective benefit from using anything but a robust bridge. In your situation you are using load with considerably more VA rating than most others would consider, or provide design details for, so I would suggest you identify a more robust bridge than a 35A rated device.

The voltage rating of the capacitors don't change from what Rod identifies.

The measurement of voltage between neutral and protective earth is not an indicator of DC current passing through the primary winding of your equipment. To get a good indication of whether DC current is being passed and is upsetting your equipment transformer, you can use a current sensor (such as a LEM type device) to observe the waveform to see if it is symmetric or has a strong assymetry and saturation related peak to the waveform. To get an idea of whether there is some DC component to the AC voltage between active and neutral then Rod provides a method of measurement.

Last edited by trobbins; 5th January 2020 at 12:55 AM.
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Old 5th January 2020, 09:44 AM   #7
Mooly is offline Mooly  United Kingdom
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Ultra high current DC blocker
Quote:
Originally Posted by montana View Post
Thank you Molly
I have red this half of it I didn't understand
Ever more questions like advantages of using at the natural wire as well I didn't saw...
You mean the neutral wire...

The transformer primary is a simple series circuit, mains in at one end and out at the other. You can place the DC blocking elements anywhere within that path.
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Old 5th January 2020, 06:23 PM   #8
montana is offline montana  Israel
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Thank you guys
Trobbins I have understand that one of the tn-s problem is that noise enters through the natural wire...
Or is it common mode noise ?
Ever more can DC enters through the ground ?
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Old 7th January 2020, 09:54 AM   #9
montana is offline montana  Israel
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I got the schematic of the ML33HL
It's looks like that the Levinson's got already DC blocker
But if I understand correctly it's not a diode bridge ???
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Old 7th January 2020, 11:25 AM   #10
trobbins is offline trobbins  Australia
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Quote:
Originally Posted by montana View Post
But if I understand correctly it's not a diode bridge ???
70HF-HFR40 refers to each individual diode shown in the schematic. The four diodes could be shown in a bridge formation, along with extra connections to achieve the same result - they just chose to draw it that way.
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