Actually and most likely there are three phases in the neighborhood. Each
transformer has a single line connected to one phase to provide step-down to
240 volts center tapped. The next group of homes will be picked off of
another phase and so on. On our street of 12 houses, there are 6
transformers with one transformer serving 2 homes. Hence, there are 2
transformers per phase.
Yes, be sure all equipment is bonded by a separate ground wire, chassis to
power supply of that station. In my case, having 2 separate stations on the
desk they have the equipment bonded back to the power supply of each
station. I do not loop from chassis to chassis. That says I have 5 or 6
ground wires connected to a common point on the power supply. It doesn't
require "killer size" wire. Just some #12 AWG copper such as auto primary
wire is used. I apply lugs with them being crimped and soldered at each
end. I prefer the VACO brand of lugs.
Now the next thing is power to the station. Again in my case, covering
approximately 75 ft. distance from the breaker panel, I bring a #10 x 4
conductor to a break-out group of outlets. The breaker in the panel is 30A
double pole. The #10 x 4 then is defined as L1, L2, Neutral and Ground.
Although Neutral and Ground are connected to a common buss bar in the
breaker panel, ground never carries current except in the instance of a
primary fault where Neutral carries only the difference in current between
L1 and L2. In all cases, 3rd pin equipment ground is in place. This
configuration is used to provide 240 volts to a single 20A 240V outlet for
the amp. Then I use L1, Neutral and Ground for three duplex outlets in a
box, and then L2, Neutral and Ground for a 2nd set of duplex outlets in a
box. I do not have an external station ground due to the location of the
equipment in the residence. All lightning protection is done at the point
where the feedlines and rotor cables enter the structure. {Topic for
another discussion.}
All this makes for clean power, no ground loops, and a very safe
installation.
73
Bob K4TAX
----- Original Message -----
From: "Gary Hoffman" <ghoffman@spacetech.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Thursday, April 02, 2009 8:50 PM
Subject: Re: [TenTec] Corsair II buzz
Hmmm....in our neighborhood we certainly have nothing remotely like a 240
v
delta system serving residences, being center tapped and all as mentioned
below.
What we have are moderately high voltage lines - on my street they are at
like 3400 volts, phase to phase. While three phases are available, only
two
are run down my street, because that is all they need for our low power
use.
Local transformers, that service a couple of houses each, pick off power
from these two primary phases, and produce a center tapped 240 V AC
secondary.
If there were a buzz around here, it sure would not be due to the source
described.
----- Original Message -----
From: "Jim Brown" <k9yc@audiosystemsgroup.com>
To: <Gary@doctorgary.net>; "Discussion of Ten-Tec Equipment"
<tentec@contesting.com>
Sent: Thursday, April 02, 2009 9:13 PM
Subject: Re: [TenTec] Corsair II buzz
Gary Smith wrote:
Thanks
I have noticed the "buzz" on several different power supplies
including a deep cycle battery. It's definitely not a hum but sounds
like something with odd harmonics, a definite buzz.
The most common source of "buzz" consists of "triplen" harmonics of the
AC power line, coupled from the 3-phase power line that is probably
providing your residential service. See my recommendations for bonding
together the gear in your station to kill this noise. Triplen harmonics
are harmonics whose orders are divisible by three -- 180 Hz, 360 Hz, 540
Hz, and so on.
http://audiosystemsgroup.com/RFI-Ham.pdf and
http://audiosystemsgroup.com/HamInterfacing.pdf
The first one is a tutorial in text form that covers a lot of material,
including this. The second is a Power Point that covers much of the same
material.
My solutions are very simple and inexpensive, and don't involve going
inside the radio.
These harmonics are produced in power systems by current flowing at the
peak of the cycle to charge the input filter capacitors in electronic
power supplies (both linear and switchers). Most current cancels in the
neutral (and in the green wires) of 3-phase systems, but triplen
harmonics add. So-called "high leg Delta" power distribution is widely
used in neighborhoods where a few small users need 3-phase but most need
120/240V. It's a 240V Delta, but with one side being center-tapped to
feed residences. This triplen current is the source of what we call
"ground buzz." It's there because there's no neutral feed to those
3-phase users, so all their triplen current goes to ground in the
neutral for residences!
This is yet another reason why it's a very good thing to bond all
grounds together (the most important being lightning). To learn more see
the tutorials.
73,
Jim Brown K9YC
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|