KPA-1500 Efficiency As A Function of Input Power
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Thanks for the replies.
Upon further testing, I have found that the efficiency of the KPA-1500 is varies greatly with driving power. The following table illustrates the relationships between exciter power, voltage, current, power-in(voltage x amps), power-out, efficiency, and dissipated power. The following test was made with the KPA-1500 into a dummy load and readings from the KPA-1500 utility software. (Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin) (Dissipated Pwr) 10w 29a 52.7v 1528w 375W 375/1528 = 24.5% 1205w 15w 37a 52.7v 1950w 620w 620/1950 = 31.7% 1335w 20w 43a 52.6v 2262w 861w 861/2262 = 38.0% 1413w 25w 47a 52.6v 2472w 1060w 1060/2472 = 42.8% 1451w 30w 51a 52.6v 2682w 1227w 1227/2682 = 45.7% 1420w 35w 53a 52.5v 2782w 1380w 1380/2782 = 49.5% 1412w 40w 55a 52.5v 2887w 1497w 1497/2887 = 51.9% 1382w 45w 56a 52.5v 2940w 1600w 1600/2940 = 54.4% 1313w 50w 57a 52.5v 2992w 1703w 1703/2992 = 56.9% 1315w 53w 59a 52.5v 3097w 1825w 1825/3097 = 58.9% 1306w The remarkable thing is that DISSIPATED POWER appears to be relatively constant from 375w output through 1825w output. This implies the KPA-1500 will need to dissipate nearly the same amount of heat at low power output as at high power output, if I am interpreting the data correctly. I would like to know from Elecraft if this is normal behavior. Charles K5UA ______________________________________________________________ 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 Message delivered to [hidden email] |
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There was a similar post about the KPA500 in the last year or so. Elecraft responded that the amp was designed for 500 Watts running less was less efficient and running amp at low power was doing it no favors.
With the KPA500, so many wanted 1500 W so now you have it, you want to run less? Sent from my iPhone ...nr4c. bill > On Aug 17, 2018, at 1:17 AM, [hidden email] wrote: > > Thanks for the replies. > > Upon further testing, I have found that the efficiency of the KPA-1500 is varies greatly with driving power. The following table illustrates the relationships between exciter power, voltage, current, power-in(voltage x amps), power-out, efficiency, and dissipated power. The following test was made with the KPA-1500 into a dummy load and readings from the KPA-1500 utility software. > > (Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin) (Dissipated Pwr) > 10w 29a 52.7v 1528w 375W 375/1528 = 24.5% 1205w > 15w 37a 52.7v 1950w 620w 620/1950 = 31.7% 1335w > 20w 43a 52.6v 2262w 861w 861/2262 = 38.0% 1413w > 25w 47a 52.6v 2472w 1060w 1060/2472 = 42.8% 1451w > 30w 51a 52.6v 2682w 1227w 1227/2682 = 45.7% 1420w > 35w 53a 52.5v 2782w 1380w 1380/2782 = 49.5% 1412w > 40w 55a 52.5v 2887w 1497w 1497/2887 = 51.9% 1382w > 45w 56a 52.5v 2940w 1600w 1600/2940 = 54.4% 1313w > 50w 57a 52.5v 2992w 1703w 1703/2992 = 56.9% 1315w > 53w 59a 52.5v 3097w 1825w 1825/3097 = 58.9% 1306w > > The remarkable thing is that DISSIPATED POWER appears to be relatively constant from 375w output through 1825w output. This implies the KPA-1500 will need to dissipate nearly the same amount of heat at low power output as at high power output, if I am interpreting the data correctly. I would like to know from Elecraft if this is normal behavior. > > Charles K5UA > ______________________________________________________________ > 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 > Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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" Upon further testing, I have found that the efficiency of the KPA-1500 is varies greatly with driving power." That's the reason SPE amps have a power range selection choice setting. (Me thinks) 73, Roy K6XK ______________________________________________________________ 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 Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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In reply to this post by charles-2
It's normal.
Even at zero output, (keyed ON but with no drive power) the idling current required to obtain linear class amplification will cause significant power dissipation in the final, regardless if its solid or hollow state. 73, Charlie k3ICH -----Original Message----- From: [hidden email] <[hidden email]> On Behalf Of [hidden email] Sent: Friday, August 17, 2018 1:18 AM To: [hidden email] Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power Thanks for the replies. Upon further testing, I have found that the efficiency of the KPA-1500 is varies greatly with driving power. The following table illustrates the relationships between exciter power, voltage, current, power-in(voltage x amps), power-out, efficiency, and dissipated power. The following test was made with the KPA-1500 into a dummy load and readings from the KPA-1500 utility software. (Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin) (Dissipated Pwr) 10w 29a 52.7v 1528w 375W 375/1528 = 24.5% 1205w 15w 37a 52.7v 1950w 620w 620/1950 = 31.7% 1335w 20w 43a 52.6v 2262w 861w 861/2262 = 38.0% 1413w 25w 47a 52.6v 2472w 1060w 1060/2472 = 42.8% 1451w 30w 51a 52.6v 2682w 1227w 1227/2682 = 45.7% 1420w 35w 53a 52.5v 2782w 1380w 1380/2782 = 49.5% 1412w 40w 55a 52.5v 2887w 1497w 1497/2887 = 51.9% 1382w 45w 56a 52.5v 2940w 1600w 1600/2940 = 54.4% 1313w 50w 57a 52.5v 2992w 1703w 1703/2992 = 56.9% 1315w 53w 59a 52.5v 3097w 1825w 1825/3097 = 58.9% 1306w The remarkable thing is that DISSIPATED POWER appears to be relatively constant from 375w output through 1825w output. This implies the KPA-1500 will need to dissipate nearly the same amount of heat at low power output as at high power output, if I am interpreting the data correctly. I would like to know from Elecraft if this is normal behavior. Charles K5UA ______________________________________________________________ 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 Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by charles-2
I believe most every electrical device and piece of equipment will have some
type efficiency curve for power in and power out. A motor sitting at idle is using power, but doing almost no real work. However, at no load it is still using watts. Typically a motor has the best efficiency at around 75% load or so. I am sure an amplifier or any electronic device is similar to a motor or transformer. There are always "no load losses", that you need to have regardless of the load on the device or output of the device. Also, I am not sure you are looking at the entire picture with your numbers. I see that you are multiplying the DC amperes x DC volts. In reality, the power supply has to make that DC power, and it also has some electrical power loss. You should really use a power meter on the 240V feed from your panel to get the exact input power required for the KPA-1500. That is why Elecraft recommends a 20A feeder at nominal 240V input. The range of the power supply is 195V to 250V. At maximum power output of the amp there will be less amperes used at 250V than 195V but it will require the same input power. There is a maximum power dissipation hard fault @ 2050 watts. So, that would say if you are dissipating 2050 watts, and putting out 1500 watts RF, that would require 3550 watts of input power. At 240V that is about 15 amps and at 195V that is over 18 amps. You don't want to run it that high or at that efficiency. You need to make some changes in your setup to keep below that level. The calculations are even worse for the "efficiency" using the power used on the 240V side, but that is what you are really paying for in your monthly electric bill. What you did probably is close enough for discussion and Elecraft metering reflects those numbers, but it is worth noting there are many factors that enter into an "efficiency" calculation. Loading the amp into a dummy load gives you one set of data. However, the better your antenna matches at each frequency without needing the tuner, the less heat the tuner will create doing it's job to match to 50 ohms, so the amp can put out maximum power. Of course, if your antenna has a high SWR, because of it's electrical design, you are just making heat somewhere, and not putting your power used to good RF output production for getting your station heard on the airwaves. Bill, K8ZCT -- Sent from: http://elecraft.365791.n2.nabble.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 Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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In reply to this post by charles-2
Not sure why that's a surprise. It's a linear amp ... the bias point is what draws the current, and therefore essentially determines the dissipation. There's nothing remarkable about it. Amplifier 101. Dave AB7E On 8/16/2018 10:17 PM, [hidden email] wrote: > Thanks for the replies. > > Upon further testing, I have found that the efficiency of the KPA-1500 > is varies greatly with driving power. The following table illustrates > the relationships between exciter power, voltage, current, > power-in(voltage x amps), power-out, efficiency, and dissipated power. > The following test was made with the KPA-1500 into a dummy load and > readings from the KPA-1500 utility software. > > (Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin) > (Dissipated Pwr) > 10w 29a 52.7v 1528w 375W 375/1528 = > 24.5% 1205w > 15w 37a 52.7v 1950w 620w 620/1950 = > 31.7% 1335w > 20w 43a 52.6v 2262w 861w 861/2262 = > 38.0% 1413w > 25w 47a 52.6v 2472w 1060w 1060/2472 = > 42.8% 1451w > 30w 51a 52.6v 2682w 1227w 1227/2682 = > 45.7% 1420w > 35w 53a 52.5v 2782w 1380w 1380/2782 = > 49.5% 1412w > 40w 55a 52.5v 2887w 1497w 1497/2887 = > 51.9% 1382w > 45w 56a 52.5v 2940w 1600w 1600/2940 = > 54.4% 1313w > 50w 57a 52.5v 2992w 1703w 1703/2992 = > 56.9% 1315w > 53w 59a 52.5v 3097w 1825w 1825/3097 = > 58.9% 1306w > > The remarkable thing is that DISSIPATED POWER appears to be relatively > constant from 375w output through 1825w output. This implies the > KPA-1500 will need to dissipate nearly the same amount of heat at low > power output as at high power output, if I am interpreting the data > correctly. I would like to know from Elecraft if this is normal behavior. > > Charles K5UA > ______________________________________________________________ > 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 > Message delivered to [hidden email] > ______________________________________________________________ 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 Message delivered to [hidden email] |
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