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Old 5th August 2004, 05:03 PM   #1
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Default choke current rating

Hi,

Is a choke like 10H/100mA rated at maximum current of 100mA or it has an inductance of 10H at 100mA ?

Thanks...

MB
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Old 5th August 2004, 07:50 PM   #2
gsmok is offline gsmok  Poland
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Hi
In my opinion it is rated at maximum (or rather average) 100mA current.
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Old 5th August 2004, 09:23 PM   #3
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Most likely equal to or somewhat greater than that value at rated current. I haven't purchased any Hammond chokes but they do a good job of everything else. If yours is Hammond, that is...

And then there's swinging chokes...

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Old 6th August 2004, 11:49 AM   #4
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A Class A output stage requires 80mA idle current, and the current swings between 20mA-160mA. Do you select a choke with 100mA or 200mA rating ?
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Old 6th August 2004, 04:13 PM   #5
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Average current only. High current periods cancel out against the low current periods.

Tim
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Old 6th August 2004, 05:02 PM   #6
EC8010 is offline EC8010  United Kingdom
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Agreed, a 100mA choke is fine. The unspoken assumption is that the choke is followed by a capacitor that averages those 20 - 160mA swings to 80mA. In general, chokes tend to be rated by the maximum DC current that can be drawn through them, and the inductance is often given at this value of current.

Beware that a choke input supply can cause a peak current through the choke that is rather higher than the DC load current because of the AC current flowing through the choke and to ground via the following capacitor. PSUD is very handy for quickly checking this. The choke's rating needs to be greater than the peak current in operation.
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Old 6th August 2004, 05:05 PM   #7
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Default Choke input supply...

Use a very good quality (and over-spec'd) cap for choke input supplies - otherwise they tend to buzz like crazy!

Tube Stuff
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Old 6th August 2004, 05:59 PM   #8
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OK. So we need to select a choke rated for dc current only (this is the way it is designed, and it is logical then).

> Use a very good quality (and over-spec'd) cap for choke input
> supplies - otherwise they tend to buzz like crazy!

Film capacitor like solen is good enough ?

What is the effect of power supply transient response ? Does it need to be overdamped or underdamped or does it matter ?

Radiatron designers handbook says the inductance of the choke must be greater than (Rs + Rl) / 942 (that is for 50hz). Do you use this formulae to select choke value ?
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Old 6th August 2004, 07:50 PM   #9
EC8010 is offline EC8010  United Kingdom
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Quote:
Originally posted by metebalci
OK. So we need to select a choke rated for dc current only (this is the way it is designed, and it is logical then).
This may be a language problem. Chokes are usually rated for DC current, but just because you are passing a DC current within their rating doesn't mean that you can't overload them with an additional AC current. The current peaks must be less that the DC rating.

Any old rubbish capacitor will do. (I just know that this will incur the wrath of the gods.)

An LC filter in a power supply is a resonant circuit. Whether it actually rings is another matter. My personal opinion is that things that ring are not good, and should be avoided - critical damping is a possibility (Q = 0.5).

You'll need to give a page reference for your RDH comment.
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Old 7th August 2004, 01:00 AM   #10
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Whoops, I intended to say use a good quality CHOKE...

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