[Amps] Transformer question

[Robert Bonner]

That's an interesting point Jim,  However I think the spreading out of
multiple paths is the electrical shock you get on the soft part of your arm
when you're leaning against stuff and the SHOCKED DEAD feeling you get when
you are barefoot on a damp floor when touching the same device.

MY YAESU 736R...  Something went wrong in the switching supply.  I was
leaning on the rig and hooking up the coax.  There was 60V between the
chassis and the connector.  You think that didn't wake me up?

In that case the rig had its Neutral and Green safety ground, it lit me up
anyway.  There was something seriously wrong.  I DYKED out the internal AC
supply and power the radio from the DC supply only.

If all circuit breakers were Ground Fault Interrupters, there would never be
a problem.  Ground conducts and the breaker pops.  This is not the case
however.

Anybody ever have a GFI breaker/ outlet explode?  I have.  RF on 80 meters
and all of a sudden the GFI wall outlet in the bathroom with my wife
connected with her curling iron blew out of the wall.

I love 80 meters.

BOB DD

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Jim Brown
Sent: Monday, July 09, 2007 5:56 PM
To: Amps Amps
Subject: Re: [Amps] Transformer question

On Sun, 8 Jul 2007 21:25:22 -0400, Tom W8JI wrote:

>It appears there may be some confusion about what a neutral 
>and a ground are.

Tom's reading of NEC is the same as mine.  

However -- I have heard that there used to be some exception for 
certain heavy appliances. If that execption exists, perhaps 
someone could cite the specific paragraph. 

There is a VERY good reason for the requirement that the equipment 
ground not be a current carrying conductor, and that the neutral 
be bonded at one, and only one point. The principal reason is 
leakage flux and inductance of the return path for load current. 
If the neutral carries all of the load current, all of the flux is 
confined in a small area between the phase and neutral conductors.

If, however, ground is a return path, the return current divides 
between neutral and "the building" -- that is, all of the parallel 
ground paths -- according to ohms law. in that condition, most of 
the load current will NOT be in the neutral, so most of the flux 
will be leakage flux that spreads out over the entire cross 
sectional area of the path. This can establish a massive hum field 
(depending on the magnitude of the current following that spurious 
path), which, by ordinary magnetic induction, will couple into 
lots of wires we don't want it to couple into. Like the shields of 
interconnect audio wiring, and the returns of RS232 cables, and so 
on. 

73,

Jim Brown K9YC


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