[Milsurplus] Triad Choke

[J. Forster]

Yes.

The voltage required is really set by the choke.  I'd go about it this way:

Get a very rough estimate of the choke inductance.

Pick the resistor so it roughly equals the choke's inductive reactance at
line frequency.

Pich the transformer voltage so you get enough DC through the choke to
saturate it.

-John

=============

>
> Richard, all -
> Question would it be as effective ?  to use a safer voltage say a 10V to
> 12V AC transformer to supply the measurement
> Voltage and current?
>
> -Thanks
> Hutch
>
> On 12/27/2010 4:44 AM, Richard Brunner wrote:
>> More:  Measuring a power filter choke on an inductance meter is not
>> useful because the inductance goes down substantially when dc passes
>> through, as in service.
>>
>> Measuring choke characteristics is easily done.  Use most any power
>> transformer with full wave rectification and no filtering.  Connect the
>> test choke in series with a resistor R of several thousand Ohms, and a
>> milliammeter from + to the transformer center tap.  Varying input
>> voltage, measure ac voltage across the choke, and resistor, and dc
>> current.  Then:
>>
>> L = (Echoke x R) / (Eresistor x 2 x pi x f)
>>
>> For 60 cycle input with full-wave rectification, 2 pi f becomes 2 x 3.14
>> x 120, or 754
>> Now L = (Echoke x R) / (Eresistor x 754)
>>
>> Measure ac voltage with an average reading (VOM) meter.  Use a blocking
>> capacitor to keep dc off the meter.
>>
>> As you increase the current you will see the voltage increase levelling
>> off, indicating you are getting into saturation, and is approximately
>> the useful current limit.
>>
>> References:
>> "Measuring Inductance of DC Loaded Chokes," J. H. Ellison, W6AOI, QST,
>> Feb. 1963 pp16, 17.
>> "Know Your Filter Choke Coils," Harold Reed, W3EJP, CQ, Nov. 1959, pp
>> 50, 51.
>>
>> Richard, AA1P
>>
>>
>>
>>
>> On Sun, 2010-12-26 at 13:08 -0500, n2lxm at juno.com wrote:
>>> Good Afternoon All,
>>>
>>>          While looking through the supply closet for a project on the
>>> bench I found a Triad choke I can't ID. The only markings on it is
>>> 30L4.
>>> I guess I had measured it on a LC Meter at one time, as there's a note
>>> on
>>> the bottom of 11 Hy. Can Anyone ID this choke, I really just need to
>>> know
>>> the current rating. Thanks, and I hope everyone had a Merry Christmas.
>>>
>>>
>>>                                  Jeff N2LXM
>>>                    AMATEUR RADIO OPERATOR
>>>                                  AMERICAN
>>>                                    PATRIOT
>>>                    Proud Father of two US MARINES
>>
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