120 vs 240
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I think that the argument of 120 volts compared to 240 volts is no longer and issue. Modern day houses and circuits require that 120-130 volt outlets provide at least 20 amps. Now, a reasonable 500 to 600 watt amplifier (such as the AL811 and AL-811H, the SB-200, some of the old Yaesu amps) would run fine on today's 120 volt circuit. We do this all the time with portable heaters, window AC units (about 8 amps) etc. The amp is not going to be pulling 20 amps at 120-130 volts. I think there is an average there on CW and SSB. RTTY...of course power down. But, I am sure that this is really a non issue. Lee In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense divine? Common Sense is the image of the Creator expressing revealed truth in my mind. - John W. (Kansas) ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Well, I agree that 120 VAC circuits can handle the 500 watt out or 1200 watt
input, I prefer to make sure that there is more than one 20 circuit available. I typically will run a separate circuit for what I consider High loads and another for everything else. Mel, K6KBE ________________________________ From: Lee Buller <[hidden email]> To: Elecraft Reflector <[hidden email]> Sent: Tue, January 25, 2011 9:53:57 AM Subject: [Elecraft] 120 vs 240 I think that the argument of 120 volts compared to 240 volts is no longer and issue. Modern day houses and circuits require that 120-130 volt outlets provide at least 20 amps. Now, a reasonable 500 to 600 watt amplifier (such as the AL811 and AL-811H, the SB-200, some of the old Yaesu amps) would run fine on today's 120 volt circuit. We do this all the time with portable heaters, window AC units (about 8 amps) etc. The amp is not going to be pulling 20 amps at 120-130 volts. I think there is an average there on CW and SSB. RTTY...of course power down. But, I am sure that this is really a non issue. Lee In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense divine? Common Sense is the image of the Creator expressing revealed truth in my mind. - John W. (Kansas) ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by k0wa@swbell.net
> We do this all the time with portable heaters, window
> AC units (about 8 amps) etc. The quality of the 120V run makes a big difference. For example, if it's a 15A branch circuit feeding multiple outlets across several rooms -- and if wiring is formed with pressure-contact receptacles, -- and the receptacle you need is on the end of the string, don't count on a stiff supply. By contrast, if a dedicated 20A branch circuit is run only to the shack, uses clamp terminals, and the feed is shared between the amp and a few low-current devices, then output power should be more predictable with minimal voltage sag at the 500W level. Anyone considering a new 120V circuit to the shack to avoid these problems (in my case it was dimming lights) may want to consider pulling a companion 4-wire 240V circuit to handle all commercial amps, new and old. Paul, W9AC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Mel
On 25 Jan 2011 at 10:00, Mel Farrer wrote:
> Well, I agree that 120 VAC circuits can handle the 500 watt out or 1200 > watt input, I prefer to make sure that there is more than one 20 circuit > available. I typically will run a separate circuit for what I consider > High loads and another for everything else. > For those of us outside your country we certainly want the KPA500 to work on 230V, and 50Hz as well ....... 120V ain't much use to us... (and this amp is one piece of Elecraft gear I can confidently say I will never be buying. I can work all I want with 5W). 73 Dave G3YMC http://www.davesergeant.com ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by P.B. Christensen
Don't forget about the power factor. The simple power supplies in most tube-type amplifiers have pretty low power factors. I've never measured it, but my AL-82 once blew the 15 A 240 V fuses, which suggests PF was less than about 0.7.
As the KPA-500 uses an unregulated 60 V linear supply (just like the HV supplies in the tube-type amplifiers), it probably also has a power factor in the 0.7 range, and probably draws 11-12 A at 120 V. A dedicated 20 A circuit would improve regulation. 73, Scott K9MA Scott Ellington Madison, Wisconsin USA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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On 1/25/2011 10:37 AM, Scott Ellington wrote:
> but my AL-82 once blew the 15 A 240 V fuses, which suggests PF was less than about 0.7. There are now two elements to power factor -- the phase angle at 60 Hz and the impulsive (non-sine wave) nature of the AC line current due to the input filter capacitor. With any form of power supply, the impulsive current dominates the power factor More to the point, the main thing that blows breakers with very large power supplies is the inrush of current at turn-on to charge the input filter cap. It's a statistically random thing -- if the turn-on occurs at or near zero crossing of the sine wave, the inrush current is small. If it occurs near the positive or negative peak of the sine wave, the inrush current is high and a breaker is more likely to pop. That does NOT cause any sort of destructive failure -- it's merely the inconvenience of having to get up to reset the breaker -- and it ONLY happens when the power supply is first turned on. We learned about these issues in the pro audio world about 30 years ago when audio power amps rated for up to 2kW started coming into wide use. Over the years, various methods were used to soften the turn-on transient, and/or to spread the turn-on times of a rack full of these amps over several seconds so that turning the system on didn't blow the main breaker for a building! The difference between a linear supply and a switching supply in this regard is that while they both have input filter caps, the cap in the linear supply is much larger (and the transformer is usually more robust), so the inrush current will usually be greater. There's a tutorial view of all of this in the audio section of my website. http://audiosystemsgroup.com/publish.htm 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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On Jan 25, 2011, at 1:02 PM, Jim Brown wrote: > On 1/25/2011 10:37 AM, Scott Ellington wrote: >> but my AL-82 once blew the 15 A 240 V fuses, which suggests PF was less than about 0.7. > > More to the point, the main thing that blows breakers with very large > power supplies is the inrush of current at turn-on to charge the input > filter cap. Not in this case. Anyway, the AL-82 has inrush current limiting. > > The difference between a linear supply and a switching supply in this > regard is that while they both have input filter caps, the cap in the > linear supply is much larger (and the transformer is usually more > robust), so the inrush current will usually be greater. Not necessarily. Many switching supplies simply rectify and filter the line voltage to produce 170 or 340 V DC, without even a transformer to limit the current. (All now have at least a thermistor, but they didn't always.) More expensive switching supplies have power factor correction circuitry, which inherently limits inrush current. I don't know that any of the switching supplies commonly used to power transceivers have this feature. (Virtually all computer supplies do, as required by law. How this came about is an interesting story.) 73, Scott K9MA Scott Ellington Madison, Wisconsin USA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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