[Amps] reducing the reactance of a wirewound resistor

[Fuqua, Bill L]

I had some 600 ohm Non-inductive wire would glass covered resistors a long time ago.
Dropped one and broke the outer glass covering and could see the wires on the center 
ceramic center.  There were 4 wires 2 wound C.W. and 2 wound C.C.W. with no insulation.
They made a neat cross hatch pattern on the ceramic cylinder. 
  They could have functioned two ways. One was a close simulation of a 
cylinder of resistive material if each cross connection actually made a good connection.
The other is that the magentic fields would cancel out. Possibly a combination.

73
Bill wa4lav

________________________________________
From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf Of Vic K2VCO [k2vco.vic at gmail.com]
Sent: Sunday, February 05, 2012 7:01 PM
To: amps at contesting.com
Subject: Re: [Amps] reducing the reactance of a wirewound resistor

What HB9SLV suggested was not exactly an Aryton-Perry winding, although the principle is
the same. Instead of being in parallel, his idea had the windings in series. So they will
always carry the same current!

On 2/5/2012 9:23 AM, jeff millar wrote:
> Interesting... I looked up Aryton-Perry winding as a result.  The Wikipedia
> entry pointed out ...
>
> "One disadvantage is that because the two lengths of resistive wire are
> connected in parallel, four times the length of wire (twice the length for
> each coil) is needed to make a given resistance than if a single coil was used."
>
> That led to the realization that the two windings have to carry the same current
> to have the magnetic fields cancel...which means they have to have the same
> resistance.
>
> Conclusions...
>      - start with 100 Ohm wire wound resistor
>      - count the turns
>      - wind 100 Ohms worth of copper over the same length
>      - for same turn count, need smaller diameter wire
>
> jeff, wa1hco
>
> On 02/03/2012 03:23 AM, Angel Vilaseca wrote:
>> Hi all
>>
>> I have a nice large 50 ohms wirewound resistor, which I would like to
>> use as a dummy load. Problem is, it is inductive of course.
>>
>> To cancel the inductive reactance I was thinking of winding some
>> enameled wire all along over the resistor, with as many turns as the
>> resistive wire, solder the enameled wire to the resistor terminal at one
>> end and feed the RF at the other two separate terminals (wire and
>> resistor) at the other end.
>>
>> The idea is that the inductive reactance of the resistor winding and the
>> enameled wire winding will cancel each other. With some care and
>> measuring gear the remaining reactance could be very low. The assembly
>> would then behave almost as a pure resistance.
>>
>> Of course, care should be taken not to reach too high temperatures,
>> because the enameled wire would then be damaged.
>>
>> Also, the added winding should be wound in the appropriate diraction (
>> CW or CCW depending of the winding direction of the resistive wire)
>> otherwise the two inductances would add instead ao canceling each other.
>>
>> Has anyone alredy tried this?
>>
>> 73
>>
>> Angel Vilaseca HB9SLV
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>
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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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