On 2018-04-16 7:17 PM, Don Wilhelm wrote:
> In other words, the total contact resistance of the 8 powerpole
> connectors is not as great as the resistance of 5 feet of #12 wire.
Not according to the specifications.
The specification for contact resistance of a 15A Power Pole is
0.875 milliOhms
<https://powerwerx.azureedge.net/productattachments/ds-pp1545.pdf>
The resistance of *one* 15A Power Pole connector (0.875 milliOhms)
is equivalent to 5.5 feet ( 5.5 * 1.588 / 1000 = 0.873 milliOhms) of
#12 wire.
A 10 foot #12 power cable with 15A PP connectors on both ends would
have a total loop resistance of 6.68 milliOhms (4 * 0.875 for the
connectors + 2 * 1.588 for the wire) - split almost equally between
the wire and the connectors.
73,
... Joe, W4TV
On 2018-04-16 7:17 PM, Don Wilhelm wrote:
Using a fused Rigrunner to connect from the K3 to a power supply can
cause excessive voltage drop. There are 6 points of contact. The APP
contact to the rigrunner itself (2 contacts, the negative must be
considered as well). There are 2 at the fuse contacts, and there are 2
at the the cable connecting the output of the Rigrunner. Add an
additional 2 for the connection to the K3 - that makes a total of 8.
If you consider a 1mohm contact resistance (a practical estimate), then
you have an 0.008 ohm resistance between the power supply and the K3.
At 17 amps current draw for a K3 at 100 watts, the expected IR drop
with that configuration is 0.136 volts due to contact resistance alone.
Add to that the resistance of the wire (#12 wire at 20 degC of 1.558
ohms per 1000 ft.), you have an additional 3.116 milliohms resistance in
a 5 foot cable of #12 wire - for a total of over 1.0 volts from the #12
wire.
In other words, the total contact resistance of the 8 powerpole
connectors is not as great as the resistance of 5 feet of #12 wire.
Yes, connect the the K3/K3S directly to the power supply for best
results, but if you connect through a Rigrunner,, expect some added
voltage drop.
The voltage drop through properly assembled APP connectors is low but
not zero.
73,
Don W3FPR
On 4/16/2018 4:51 PM, Joe Subich, W4TV wrote:
On 2018-04-16 4:26 PM, hawley, charles j jr wrote:
So 4 sets of power pole connectors plus 2 fuses.
Even if the power pole connectors are assembled perfectly and
mated with optimum tension, the resistance in just the four
(15 A) power pole connectors in the negative lead is equivalent
to nearly 40 feet of #12 copper wire!
The voltage at the rig, K3, now drops a volt when putting out 100
Watts.
With the equivalent of 50 feet of power cable (4 connectors plus a
10 foot physical cable), I would not be surprised. Assuming 20A
in transmit (on 15A power poles!), a 1V drop represents 0.05 Ohms
of total circuit losses .... that's pretty good for 10 feet (x2)
of cable plus eight connectors (4 in the + lead, 4 in the - lead)
and the switching device (probably a Schotkey diode). However,
the 0.05 Ohms in the negative lead is probably ten times higher
than in a braided bonding connection directly from the K3 chassis
to the power supply chassis.
I'm surprised that only 75% went through the ground path - that
indicates the ground path has 1/3 as much resistance as the "right"
(V- lead) path.
73,
... Joe, W4TV
On 2018-04-16 4:26 PM, hawley, charles j jr wrote:
About 75% went thru the ground path. The 10 ga to the rig went from
Astron to a battery switching device in case of power outage, to rig
runner and to rig. So 4 sets of power pole connectors plus 2 fuses.
I’m thinking of changing some of that too. The voltage at the rig,
K3, now drops a volt when putting out 100 Watts.
Chuck Jack
KE9UW
Sent from my iPhone, cjack
On Apr 16, 2018, at 3:14 PM, Wes Stewart <wes_n...@triconet.org> wrote:
I would hope that "much of the current..." wasn't really much. The
direct conductor from the negative terminal of the power supply to
the radio should carry the majority of the supply current,
Wes N7WS
On 4/15/2018 7:38 PM, hawley, charles j jr wrote:
This thread prompted me to check out my Astron vs35m. It had a
small black wire from -V connected to the bottom of the chassis.
Perhaps it could be called a case or cabinet...more importantly,
it’s what the green wire from the line cord is connected to. I
disconnected the black wire. When it was connected, much of the
current that would have passed thru the negative power wire from
the power supply to the rig was shunted thru the green power cord
wire, the ground buss bar, and other ground connections.
Chuck Jack
KE9UW
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