[Elecraft] Issue 12 re Astron Power Supply

[Joe Subich, W4TV]

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_n7ws at 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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