Re: Remote Power Supply Connection

"Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message 
news:g13o17$10ph$1@[EMAIL PROTECTED]
> Trevor Wilson wrote:
>> "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message 
>> news:g0up1a$1ap1$1@[EMAIL PROTECTED]
>>> Trevor Wilson wrote:
>>>> "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message 
>>>> news:g0rmo0$27co$1@[EMAIL PROTECTED]
>>>>>
>>>>> 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.
>>>> **And again, it is not difficult, nor expensive to deal with such 
>>>> issues. A handful of capacitors will effectively deal with any 
>>>> problems.
>>>>
>>>>
>>> Definitely not. The point is that the caps normally used to suppress 
>>> reverse spikes in semiconductor diodes do just that. The have no
effect 
>>> on the forward current spikes which are significant.
>>
>> **No.
>>
>
> Denial is not much of an argument.

**How about: Not necessarily? Better?

>
>>  With remote ac
>>> supplies these current spikes must pass through the cable and they
will 
>>> cause serioes radiation. Any attempt to stop them happening will
simply 
>>> stop the rectifiers from rectifying. That is why is is essential to
have 
>>> the rectifiers close to the transformer.
>>
>> **No.
>>
>
>
> Denial is not much of an argument.

**OK. It is not necessary to have rectifiers close to the transformer. I
set 
up a test last night, with 2 Metres of cable, connected to a transformer, 
thence to a rectifier, thence to an amplifier. An AM radio place VERY
CLOSE 
to the cable picked up some radiation. Covering the cable with an earthed 
sheild completely eliminated the noise.

>>>>>>>>>>> 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.
>>>> **Points:
>>>>
>>>> * 4.5 joules is a substantial amount of energy.
>>> No it isn't. it is 4.5 watts for one second.
>>
>> **Yes, it is. It depends on how long it takes to charge/discharge 
>> whatever capacitance is on the other side of the connector. In 0.1 Sec,

>> that is 45 Watts. In 0.01 sec, that is 450 watts. Certainly plenty of 
>> energy to damage surface treatment of most connectors. And, as I stated

>> earlier, lots of builders use considerably more capacitance than 100uF 
>> and more than 300 Volts for their power amps. 1,000uF and 700 Volts is 
>> not unheard of. And THAT is a considerable amount of energy.
>>
>>> My small rotary hammer drill
>>>> is rated at 2.5 joules per strike and can pulverise bricks.
>>> And there you have hit the nail on the head. It is not the *amount* of

>>> energy but the *rate* at which it is consumed that matters.
>>
>> **EXACTLY my point. 4.5 joules consumed in 10msec is a *lot* of energy 
>> for thinly plated connector to cope with.
>
> No, 4.5 Joules consumed in 10mS is not a lot of energy, it is a lot of 
> power.

**And it is enough to damage any plating on connectors. Imagine the damage

which could be caused by real-world power amps, employing (say) 1,000uF at

700 Volts DC.

-- 
Trevor Wilson
www.rageaudio.com.au