[Elecraft] [KPA500]KPA500 power cord question

[iain macdonnell - N6ML]

Hi Clyde,

Can we boil this down a bit? Would a 220/240V input get me more power
out of the KPA-500 (vs. a 20A 110V circuit, say)? A cleaner signal?
Less input power consumed? Anything discernible?

     ~iain / N6ML


On Tue, May 3, 2011 at 7:21 PM, Clyde Washburn <k2ue at rochester.rr.com> wrote:
> Currently the nominal voltages for most US power companies is 240/120V single phase, although in some areas 120/208V 3-phase is
> common, with 120V outlets being served by any one phase, and 208V circuits being fed across any 2 phases.  Accordingly, most US
> appliances either have specific performance ratings that differ slightly for 208V vs. 240V (resistive heaters and A/C compressors
> are a common example), or have power supply taps to accommodate either (common in electronic equipment).
>
> The major advantage of 240V operation is improved voltage regulation:  the same circuit, fed with the same wire (such as a common
> 20A 12 gauge circuit), will have the same resistance in either case.  But since the current is roughly half at 240V, the I*R drop
> will be half, which will be 1/4 the relative amount compared to the doubled voltage.  You can see that unregulated supplies will
> perform much better, if the current is high enough for line drop to be noticeable.
>
> US plugs and receptacles are rated for either 125V (max) or 250V (max), and are non-mating between voltages, for safety.  However
> 20A receptacles of ether voltage will accept 15A plugs of the same voltage, so the ideal hamshack receptacle for a linear is a
> 250V/20A receptacle wired to a 240V or 208V 20A circuit, which will also accept 15A 250V plugs, the smallest and most common type.
> Since 20A wiring and circuit breakers cost very little more than 15A, there is little point in installing 15A circuits, unless it is
> advantageous to use existing wiring in an house or building where new wire installation is difficult.  Please note that if you
> convert an existing 120V wire run to 208 or 240V, you are obligated by code (and common sense) to remark the white (formerly
> neutral) wire with red paint or tape at all points of access, to identify as a "hot" lead.  And receptacle ratings should never
> exceed the rating of the circuit they are on:  never use a 20A receptacle on a 15A circuit.
>
> In the specific case of the KPA500, it requires 1000VA (volt-amperes), so that is 8.3A at 120V, 4.8A at 208V, or 4.2A at 240V.  8.3A
> is not a particularly heavy load for a 20A circuit, but if it is a 15A circuit or is also loaded with all the other hamshack gear,
> then either a separate 120V circuit for the linear, or preferably a 240V circuit is a good idea.
>
> _____________________
> Clyde Washburn, K2UE
> 82 Lasalle Pkwy
> Victor, NY 14564-9610
> 585-317-7006
> k2ue at rochester.rr.com
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of iain macdonnell - N6ML
> Sent: Tuesday, May 03, 2011 2:21 PM
> To: K2GN
> Cc: Elecraft - K3
> Subject: Re: [Elecraft] [KPA500]KPA500 power cord question
>
> On Tue, May 3, 2011 at 5:59 PM, K2GN <k2gn at k2gn.com> wrote:
>> GA,
>>
>> I am in the process of rebuilding my shack and planning for the future.
>>
>> I will order a KPA500 and want to be ready for it power wise.
>>
>> I want to run it on 220V as it is available in a nearby panel.
>>
>> Question is:
>>
>> The manual states for 220V operation I would need an adaptor or new
>> plug on the power cord.
>>
>> Is this a choice that I have as far as wall outlet and matching plug?
>> If so, no problem, my electrician can fix it up.
>>
>> If it's some special, I need specs for it.
>
> I think that's left as an exercise for you ... find a heavy computer power cord, cut the plug off, and install one that matches your
> outlet .. or install a matching pair that you like.
>
> I'd be interested to hear about benefits (if any) of running the
> KPA-500 on 220V vs 110V (in the US)......
>
>    ~iain / N6ML
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