[Mgs] Positive ground = more rust?

Hans Duinhoven h.duinhoven at planet.nl
Fri May 23 13:46:14 MDT 2008


You gain, that the coils of solenoids and relais do not <wear> and will
generate a higher resistence in time.
When this happens, these devices will operate unreliable in time and
faultfinding to such a failure is a nightmare I can tell!

Modern electronic solutions are protected by a constant DC voltage / current
protection.
I have seen such devices connected to f.i. an electronic fuel pump
installation at a car fuel station.
It was called kathode protection.

Cheers,

Hans
  ----- Original Message -----
  From: Paul Hunt
  To: Hans Duinhoven ; mgs at autox.team.net
  Sent: Thursday, May 22, 2008 5:59 PM
  Subject: Re: [Mgs] Positive ground = more rust?


  I did 32 years in telecoms and that never came up, although the 'sacrificial
anode' thing did.  As I recall all the switching equipment used a +50v supply
and hence a negative ground.  I can't see how a length of copper wire would
lose material with the current flowing in one direction but not the other.
Even with contacts one gets a pit and the other a spike, reverse the direction
and the pits and spike change places, but what do you gain?

  PaulH.
    ----- Original Message -----
    ... I have been tought,
    that phone switching equipment like coils and solenoids should be operated
    with the ground connected to the positve power.


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