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Old 27th June 2007, 03:50 AM   #1
jarthel is offline jarthel  Australia
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Default common-mode chokes

I was looking at Thorsten's site and he uses these on the power supply.

I know that lundahl has them on its catalog. Do these function similar to a "normal" power supply choke?

Thank you.
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Old 27th June 2007, 06:51 AM   #2
cerrem is offline cerrem  United States
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The common mode choke is a "bifilar" or balun type choke at the input of the power line....
There is winding in the feed and return line and the net DC flux in the core is zero due to the way the windings traverse....
It is used to meet certain EMI requirements or audio susceptibility requirements.... It is used in conjunction witrh Y-caps... for a -40db/Decade slope double Pole filter....

Chris
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Old 27th June 2007, 10:32 PM   #3
jarthel is offline jarthel  Australia
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Quote:
Originally posted by cerrem
The common mode choke is a "bifilar" or balun type choke at the input of the power line....
There is winding in the feed and return line and the net DC flux in the core is zero due to the way the windings traverse....
It is used to meet certain EMI requirements or audio susceptibility requirements.... It is used in conjunction witrh Y-caps... for a -40db/Decade slope double Pole filter....

Chris
But thorsten has these chokes after the rectifier.

http://www.fortunecity.com/rivendell...dison300B.html
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Old 28th June 2007, 06:35 AM   #4
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Quote:
I know that lundahl has them on its catalog. Do these function similar to a "normal" power supply choke?
Yes they do, I use a LL1673 as a common mode choke in my amp. You get a better rejection of common mode noise from the mains with a common mode choke. See the data sheet of the LL1673 for more information.

Quote:
The common mode choke is a "bifilar" or balun type choke at the input of the power line....
You are referring to those little chokes that are used in switching power supplies. These are very different beasties, they are for reducing HF noise and will not reduce the 100Hz or 120Hz ripple in the power supply.
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Old 11th February 2008, 02:15 PM   #5
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Gerrit,

If I have a common mode choke, can I connect the two coils in series using it a a simple/single line choke? If so, does it halve the allowed current?

Jan Didden
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Old 11th February 2008, 03:21 PM   #6
JoshK is offline JoshK  Canada
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I've been studying this concept for some time and in more detail recently.

My question is how would one model this 20H Lundahl CMC in PSUDII?
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Old 11th February 2008, 03:31 PM   #7
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Hi Jan,

According to the LL1673 specsheet the two chokes are in series when you use it as a common mode choke, it's just that the two chokes are not 'in the same leg'. So if you use it as a normal serial choke, the inductance and rated current stay the same.
As for modelling in PSUDII, use the values for a serial connection.

LL1673 specifications and connections
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