The important point is whether the voltage to the finals at full output is as different when the KPA500 is supplied by 240 or 120V mains. I believe the answer is "no". AFAIK, the KPA500, and it's power supply, was designed and tested to meet all of its performance specifications with either a 120V or 240V mains supply.
There's a reason why 240V is so popular as the standard mains voltage throughout most of Europe for virtually everything in the home. It does make things easier, especially when handling heavy loads. But that does not mean it justifies the expense of new wiring to operate the KPA500. Ron AC7AC -----Original Message----- From: Joe Subich, W4TV [mailto:[email protected]] Sent: Tuesday, May 03, 2011 2:19 PM To: Ron D'Eau Claire Cc: 'iain macdonnell - N6ML'; 'Clyde Washburn'; 'Elecraft - K3' Subject: Re: [Elecraft] [KPA500]KPA500 power cord question > No. The KPA500 peak demand is less from your 120 volt outlet than > most household vacuum cleaners or window air conditioners. And, > unless you are running a full-carrier mode, the average demand by > your KPA500 is far below the peak. While the average current requirement may be less that the typical vacuum cleaner or window air conditioner, the peak current demand *will* be significantly higher if the KPA-500 has a capacitor input filter in the (analog) power supply. What Ron refers to as "peak" is a long term (multi-cycle) peak current and that is much less than the true instantaneous peak current in a "linear" capacitor input filter power supply. Depending on the conduction angle of the rectifier/capacitor circuit, instantaneous peak currents use can be many times the average current requirement - and significantly higher than the multi-cycle peak current one would read on an amp meter in the supply line. It is the instantaneous peak current use that drives losses in the supply wiring and thus the effective source voltage regulation while it is the longer term currents (and duty cycle) that impact heating. Even with a relatively low power (average current < 10A), the peak currents can easily exceed 50A unless the power supply includes "power factor correction". While this will not trip breakers or even cause heating in the wiring because of the very short duration, with even 0.5 Ohms of resistance in the power lines, connectors, etc. 50 A peak currents can result in significant "short term" (partial cycle) voltage drops. Reducing the voltage drop in the supply by half is *always* a good idea. Using 240V instead of 120V - particularly if it is already available - is never a bad idea and certainly worth sacrificing an inexpensive IEC cable by cutting off the 115V plug and replacing it with the proper 240V/15A plug (often known as an "air conditioner" plug after the old window air conditioners that required 220V/15A). 73, ... Joe, W4TV ______________________________________________________________ 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
