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 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] 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 <[email protected]> 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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
