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Bleeder resister size

colum

Jul 25, 2013
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I want to put a resister accross a DC supply leads to discharge the voltage in the capacitors. This will be only used to discharge after each useage. I expect the voltage to be from 1 to 125v DC and the amperage to max of 3 amps.
I checked all of my books and the internet and I could not find any info on size and from my limited knowledge I understand you should not discharge a cap too fast...Thanks...colum ( I its too late to put an internal res accross the cap)
 

davenn

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Sep 5, 2009
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from what I have seen across big caps in amplifier PSU's running at ~ 50 to 70VDC something up ~ 10k , 1/2 Watt would be OK

cheers
Dave
 

BobK

Jan 5, 2010
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from what I have seen across big caps in amplifier PSU's running at ~ 50 to 70VDC something up ~ 10k , 1/2 Watt would be OK

cheers
Dave
Sorry, Dave, but at 125V a 10K resistor will dissipate 1.6 Watts. A 1/2 W resistor ain't going to make it.

Bob
 

colum

Jul 25, 2013
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Sorry, Dave, but at 125V a 10K resistor will dissipate 1.6 Watts. A 1/2 W resistor ain't going to make it.

Bob

Hi Bob. Since this is just for bleeding a capacitor thats disconnected from the power supply would it make a difference and would a permanently installed bleeder require different ratings..Thanks...colum
 

BobK

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If the resistor is connected all the time, it would have to be at least 2W. If you only connect when it is powered off, I suppose you could get by with less.

Bob
 

davenn

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OK so up the wattage rating a bit :)

D
 
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