Carbon Pile

Maynard A. Philbrook Jr. used his keyboard to write :
> In article <9oGdncjuh_FYc-bOnZ2dnUVZ_qWdnZ2d@westnet.com.au>, 
> greentest@ozemail.com.au says...
>> 
>> wanderer wrote :
>>> On Wednesday, May 14, 2014 7:21:42 PM UTC-4, OldGuy wrote:
>>>> Who makes a good stable carbon pile?
>>>> 
>>>> Stable as in it maintains its resistance as current is varied.
>>>> 
>>>> 200 amp range, 100 VDC.
>>>> 
>>>> Currently using a battery load tester but I want something I can mount 
>>>> 
>>>> on my own equipment.
>>>> 
>>>> 
>>>> 
>>>> e.g. I have DC motor that I want to voltage up to see how it draws.
>>> 
>>> Look for sewing machine foot pedals. The old ones had carbon piles and the 
>>> new ones might be an alternative to carbon piles.
>> 
>> The OP said 200 (TWO HUNDRED) amps.
>> Nothing mentioned so far comes anywhere near being capable of 200 AMPS. 
>> :-?
>
> Large variac with rectifier ?
>
> Jamie

20KVA  is a big Variac and a big rectifier.
I wonder if the OP really meant such a large job? :-Z

-- 
John G

OldGuy <spamnot@nospam.com> wrote:

> Who makes a good stable carbon pile?
> Stable as in it maintains its resistance as current is varied.
> 200 amp range, 100 VDC.
> Currently using a battery load tester but I want something I can mount
> on my own equipment.
> 
> e.g. I have DC motor that I want to voltage up to see how it draws.

I don't think a carbon pile would be particularly stable, especially as
it heats up.  You could include it in a feedback loop and use an
electromagnet to vary the pressure so as to keep it stable, but that
would involve some way of monitoring its resistance.

For low resistance high current purposes, big wirewound resistors with
multiple tappings are the cheapest and most stable answer.  They are
relatively easy to construct from slate bars and resistance wire, but
the tapping switch is going to be the most difficult item to design and
make.

If you want to go down this route, please ask for more information.  I
have made several 5 kW* units as replacements in motor-starting
applications, so I may be able to help.

http://www.poppyrecords.co.uk/other/images/CBAT01_0937s.jpg




*Intermittent rating.

-- 
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

On Tue, 20 May 2014 21:31:44 -0400, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:


>> The OP said 200 (TWO HUNDRED) amps.
>> Nothing mentioned so far comes anywhere near being capable of 200 AMPS. 
>> :-?
>
>Large variac with rectifier ?

OP already has the power supply and motor.  A carbon pile rheostat is
the perfect solution to this problem.  I have such a beast but I'm not
parting with it :-)

I spent part of yesterday looking for a modern day carbon pile maker
for another problem.  Couldn't find one, though I ran into a couple of
custom resistor companies who could probably make them.

To the OP:  Try Alibaba.com.  If they're still made, the ChiComs or
the Indians will make them.

If you really can't find one then you might take a look at some of the
less expensive EV motor controllers.  Still several hundred dollars
but a positive and stable solution.

John
John DeArmond
http://www.neon-john.com
http://www.fluxeon.com 
Tellico Plains, Occupied TN
See website for email address