Re: Remote Power Supply Connection

flipper wrote:
> On Sun, 18 May 2008 07:36:56 +1000, "Trevor Wilson"
> <trevor@[EMAIL PROTECTED]
> wrote:
> 
>> "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message 
>> news:g0mu6g$2vgp$1@[EMAIL PROTECTED]
>>> Trevor Wilson wrote:
>>>> **Asked and answered. Use AC. Do not use DC.
>>>>
>>> In practice that is perhaps not such a good idea as it sounds. It
means 
>>> the rectifiers will be at the end of a fairly long piece of cable. The

>>> large rate of changes of current caused by rectifiers (especially the 
>>> semiconductor type) combined with the series inductance of the cable
is a 
>>> recipe for noise, interference and possibly stability problems.
>> **I fail to see how. In practice rectifiers are already at the end of
very 
>> long cables and are supplied by devices with prodigious inductance.

Not true. The rectifiers are quite close to their transformer in normal 
cir***stances. Any noise they create has to be transferred back through 
the transformer and is therefore severely attenuated before it meets the 
mains cable which is what I think you you are referring to a 'very long 
cables'. With the method you propose the rectifier currents flow 
directly in the 'very long cable'

>>In any 
>> case, there are measures that can be taken to reduce the problems
associated 
>> with noise from diodes. There are even (easy) measures which can be
taken to 
>> reduce the inductance of those connecting cables. What I am very
concerned 
>> about is the extreme ignorance displayed about the dangers associated
with 
>> DC arcs and connectors. This, as opposed to your hypothetical, is a
very 
>> real possibility. Read this:
>>
>> http://www.arcadvisor.com/faq/dc_direct_current_arc.html
>>

This clearly shows that at low currents (e.g HT currents) and high 
voltages (e.g.HT voltages) dc arcing is very unlikely to occur.

It also clearly shows that at modest currents (a few amps of heater 
current) and low voltages (less than 20 volts)  dc arcing will  not occur.

Cheers

Ian