Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Charles, It is just like your car. You get great gas mileage at certain speeds and driving methods. Worse is at lower speeds, stop and go, and 55 -65 Mph is a good speed for having an efficient mileage car. However, 70-80 is worse on the mileage. Everything has a sweet spot. Nothing is for free as it takes power to do work or in this case to output RF. The front end of the process always has some requirements to get things moving that do little for you, but you got to have them. Does this make any sense? I don't mean to a smart, I am just trying to relate this in a different way that you are probably familiar with. I don't operate RTTY, but it is one of the hardest modes on the equipment similar to AM or FM. I would guess it is a duty cycle requirement, so the equipment doesn't melt down or to not create splatter issues. RTTY equipment needs to be properly adjusted for decoding similar to FT8. 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency
I would think these RF input versus RF output numbers are reasonable. Everyone's setup will vary for all bands. I haven't looked at the KPA-1500 Utility in a while, but "real" efficiency of the amplifier is a different calculation. Amp efficiency is Power Input versus Power Output, and per Elecraft that is somewhere around 50% or so. If you had the equipment to measurement the power input, it would be somewhere in the 3000W range I would assume with a 1500W output. That is why the fans are required and the ventilation of the unit is critical, as there is a lot of heat being dissipated to the space as was discussed in other posts. 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 - adding fans
My KPA1500 is S/N 00059. I don't operate full power all the time. I live in a compromised antenna area, and so I will use the amp as required to make contacts that are difficult assuming I can hear the station well enough to have the QSO. I have not had problems with the weird display issue that has been reported, and also someone recently replaced their antenna tuner to solve a problem which I have not seen either yet. Thanks for this site, as it gives us a heads up if we would have similar issues with our equipment. Maybe I don't run the amp hard enough, my antenna will take 1500 watts, but I probably never push it that hard for long periods. I run FT8, but with 100 watts or less and I have made plenty of contacts. FT8 is whole another discussion. SSB is the least difficult for the amp to deal with. CW is harder and RTTY, FM,FT8 and AM are the worst. The fans on the power supply make some noise, but I have had several tube amps over the last 40 years that are louder. I haven't installed the latest software update issued in July, so I need to see if that makes any difference. I was involved with the design specification, and purchase of medium and high voltage transformers for my career. Cooling of electrical equipment is a little more complex than just installing fans. There are proper air flow requirements to look at in the design, so the air doesn't get short circuited, and actually hurt the process. So more air isn't always better if it is not properly applied. Transformers have RTD's or Thermocouples imbedded in the windings to measure transformer temperature, because that is the "hottest spot" of any transformer. The hot spot temperature is made up of the ambient air temperature normally 40 C maximum is used with a 30C average over a 24 hour period, and the temperature rise of the unit under load. Most electrical equipment design is based on a 40C maximum ambient but I didn't see in the manual what Elecraft considered for a maximum. Regardless, the ambient heat around the amplifier must be controlled and not trapped around the unit. An air conditioned space or proper ventilating for area is critical. If you don't remove the heat your unit will work harder and could make more noise than other units. Wayne or Eric can comment, but RF amplifiers must follow similar laws of physics. The heat sink temperature must be maintained or the devices primarily the LDMOS final amp units will fail. There are average and maximums I would assume are used in the Elecraft design. Ambient air must be kept at a certain maximum and air flows must not be restricted. At this time, it good to provide feedback to the vendor on operational concerns of the equipment, and I did plenty of that over the years. However, I usually realized there were some people, who did this for a living, and I was a consumer maybe a smart consumer, but still I didn't design transformers as my main employment. With all the KPA1500's still under warranty I don't think it is a good idea to modify or change anything with regards to the operation, and design of the KPA1500. Again, I am not Wayne or Eric, but I think you are doing it at your risk. I will wait for Wayne and Eric to come out with improvements, and updates based on customer and other inputs, but I will not modify the KPA1500 in anyway including external programs that change the operation without the supplier approval. I guess after the warranty period anyone can do what they want, but don't expect the supplier to honor any warranty issues that may have been created due to prior modifications of operation. Just as with a transformer, cooling of an RF amplifier is critical to the proper operation and long term reliability and life of the unit. Heat is the main cause of failure of any electrical equipment! 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Power Supply Cable Size
Jim, Please accept my apologies. Sorry for giving you Kudo's for the wrong Handbook. I should have stated that you are are a contributor to the 2018 Edition of "The ARRL Handbook". I have many of your articles and to be honest the ARRL "Grounding Book" has a lot of information that is also in the National Electrical Code and IEEE "Green Book". I worked in industry for over 40 years in the power systems distribution area, and I was an active member of the IEEE IAS Power Systems Reliability Subcommittee. You are very modest about your knowledge and experience. 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Power Supply Cable Size
Jim Brown is on the National Electrical Code Committee, so he knows what he is saying and I would trust his opinion 100%! I guess my thought on any remote wiring is, if your really going to go through all the effort to do the project, then do it with materials, that you know when you purchase them are going to work for the duration of the installation, and provide you a reliable and safe installation. Cost should not be your only consideration. I have never seen any detailed specifications on speaker wire, when I have bought it to wire up my audio system. However, I knew that I was using it to wire up speakers, and the speakers were not a long distance from the amplifier. If the remote run is long, voltage drop in the cable is very critical. You also should consider protecting the wiring, so you may need to think of using conduit or some type of protected raceway as having wires carrying 60V in the open is also not a good idea. I think that considering diesel locomotive wire or similar flexible cable would be a good solution. It all depends on how far away the remote supply is located from the main amplifier and where it is being routed to the final destination. Unfortunately, I have seen people try to use speaker wire or lamp cord to do provide power in crazy ways. One guy I remember years ago was a recent immigrant from Eastern Europe with no electrical knowledge although he was an engineer. He wired his entire basement with speaker wire. Of course, I politely told him that was not a good idea, and that it was against the local and National Electrical Code to install. His initial response was that he thought is was a lot easier to install than the solid wire cable called Romex. 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Power Supply Cable Size
One of previous posts recommended using speaker wire for the remote connection of the KPA-1500 amplifier to the KPA-1500 power supply. Speaker wire is made for speaker systems. Although it may look like "lamp cord" it is not listed for use to wire up a lamp. You should buy rated "lamp cord" for that purpose. I think the same applies for dc wiring. I am not the code inspector for anyone, so do what you want, but if I had a long remote power supply feed, it would be wired with the proper size cable rated for the purpose. I suppose one idea could be to splice the larger size cable required for the longer distance to the Elecraft supplied cable at the termination end of the amplifier. The power supply protection protects the smaller Elecraft wire as designed, so going back to it at the very end is not an issue. -- 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Power Supply Cable Size
I don't think speaker cable has a voltage rating for this purpose. -- 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
