Re: Remote Power Supply Connection

Trevor Wilson wrote:

-- Trevor Wilson www.rageaudio.com.au "Ian Thompson-Bell" 
<ruffrecords@[EMAIL PROTECTED]
> wrote in message 
news:g0ovq7$dq3$1@[EMAIL PROTECTED]
 > > 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'

**And reducing rectifier noise artefacts is an easy, cheap and convenient
solution. FAR easier than attempting to deal with high Voltage DC
connections.


I agree when the rectifiers are close to the transformer supplying them 
but not when they are separated from it my a couple of metres of 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.

**Remind me: How much energy is able to be stored by large (unstated 
values)
capacitors?

0.5*C*V^2

In a 100uF capacitor at 300V that's a mere 4.5 joules. Not worth 
worrying about.


Cheers

Ian