Parallel pwr supply chokes for add'l current?

rongon · 16th September 2010, 04:45 PM

A power supply choke good to over 300mA is expensive.

But I have a few pairs of 150mA chokes around. Would it be useful to parallel two 7H 150mA 140 ohm chokes to make the equivalent of a single 3.5H 300mA 70 ohm choke?

More importantly, is there a problem with this? (Other than the space it would take, extra holes in the chassis, etc.) Capacitance? Current sharing?

-=|=-

Andrew Eckhardt · 16th September 2010, 04:52 PM

Double the capacitance. It takes less wire to get the same inductance on a bigger core, which allows lower resistance and less capacitance. Other than that, halve the inductance and halve the resistance.

bob91343 · 16th September 2010, 05:00 PM

This would only work if the dc resistance of the chokes is the same. Since they seem to be, the answer is yes it would work. The down side is that, since there are two magnetic fields involved, you are wasting space. A single choke would be smaller. But, as you say, more expensive.

Andrew Eckhardt · 16th September 2010, 05:15 PM

The DC resistance deosn't absolutely have to be the same, so long as the critical inductance is met at the current the higher resistance coil will see due to the hogging from the lower one, and of course max current for the lower resistance one, and both, should not be exceeded.

rongon · 16th September 2010, 06:06 PM

Thanks for the replies.

Quote:

of course max current for the lower resistance one, and both, should not be exceeded.

So if I have two identical 7H 150mA chokes, and they're both pretty close to 140 ohms DCR (maybe one's off by 3 to 5 ohms) then those two in parallel could be safely used for 3.5H at 300mA? (I would think so.)

Or do you mean the two chokes in parallel would still only be good for 150mA, the current rating of each individual choke? (I wouldn't think so.)

I'm trying to clear out my collection of transfo's and chokes. It's time to start making things with what I already have, and I have a pair of those chokes... but I'm going to need a 300mA choke and I don't have one.

-=|=-

Andrew Eckhardt · 16th September 2010, 06:19 PM

> 300mA choke and I don't have one.

Yes you do

You got it right, paralleling two same resistances give you half the two original values. Several ohm difference will not affect design.

16th September 2010, 04:45 PM	#1
rongon diyAudio Member Join Date: Jul 2009 Location: Across the river from Rip's big old tree...	Parallel pwr supply chokes for add'l current? A power supply choke good to over 300mA is expensive. But I have a few pairs of 150mA chokes around. Would it be useful to parallel two 7H 150mA 140 ohm chokes to make the equivalent of a single 3.5H 300mA 70 ohm choke? More importantly, is there a problem with this? (Other than the space it would take, extra holes in the chassis, etc.) Capacitance? Current sharing? -=\|=-

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Hafler pwr supply caps	maxwedge	Solid State	20	8th January 2006 09:34 AM
Aleph P 1.7 pwr. supply choke clc	Shaun Perez 2	Pass Labs	5	9th November 2005 01:17 AM
Oracle pwr supply mod advice	moray james	Analogue Source	0	24th August 2005 03:32 AM
Pwr supply/transformer question	bbksv	Solid State	12	1st January 2004 03:18 AM
SIE chokes -- how much current	planet10	Tubes / Valves	55	25th July 2003 03:40 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read

16th September 2010, 04:52 PM	#2
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	Double the capacitance. It takes less wire to get the same inductance on a bigger core, which allows lower resistance and less capacitance. Other than that, halve the inductance and halve the resistance.

16th September 2010, 05:00 PM	#3
bob91343 diyAudio Member Join Date: Mar 2010	This would only work if the dc resistance of the chokes is the same. Since they seem to be, the answer is yes it would work. The down side is that, since there are two magnetic fields involved, you are wasting space. A single choke would be smaller. But, as you say, more expensive.

16th September 2010, 05:15 PM	#4
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	The DC resistance deosn't absolutely have to be the same, so long as the critical inductance is met at the current the higher resistance coil will see due to the hogging from the lower one, and of course max current for the lower resistance one, and both, should not be exceeded.

16th September 2010, 06:19 PM	#6
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	> 300mA choke and I don't have one. Yes you do You got it right, paralleling two same resistances give you half the two original values. Several ohm difference will not affect design.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)