regarding the green wire
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I think we have missed the point. Any line powered device that has a
conductive enclosure should have that enclosure bonded to the 'green wire'. It is a personnel safety issue. The KPA500 is line powered and has a metal enclosure. REPLY: Thus my point, the power supply for any radio is powered by AC and should be wired accordingly as suggested with the "green" wire. the KPA500 does *not* use a separate power supply. It has a built-in power supply and so plugs directly into the mains outlet. REPLY: Thank you. I stand corrected that the unit power is directly supplied by AC thus the need for "green" wire. A power supply transformer can't be considered to be totally isolating for safety purposes unless there is a shield between the primary and the secondary that is grounded to the primary. REPLY: I am aware of transformer supplies. I was referencing to switch-mode supplies (transformer less). I believe they have isolation between primary and secondary. Radios using this type of supply should not need the "green" wire to radio. It should go to the power supply itself as explained above. 72 Ron, wb1hga ______________________________________________________________ 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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>>"I am aware of transformer supplies. I was referencing to switch-mode
supplies (transformer less). I believe they have isolation between primary and secondary. Without a transformer? How are they getting any galvanic isolation? The transformer-less switched mode power supplies I'm familiar are most definitely _NOT_ isolated. I would like to see a design that was isolate. Mark AD5SS On Sun, Sep 4, 2011 at 4:15 PM, ron <[hidden email]> wrote: > I think we have missed the point. Any line powered device that has a > conductive enclosure should have that enclosure bonded to the 'green > wire'. It is a personnel safety issue. The KPA500 is line powered and > has a metal enclosure. > > REPLY: > Thus my point, the power supply for any radio is powered by AC and > should be wired accordingly as suggested with the "green" wire. > > > > > the KPA500 does *not* use a separate power supply. It has a built-in > power supply and so plugs directly into the mains outlet. > > REPLY: > Thank you. I stand corrected that the unit power is directly supplied by > AC thus the need for "green" wire. > > > > > A power supply transformer can't be considered to be totally isolating > for safety purposes unless there is a shield between the primary and the > secondary that is grounded to the primary. > > > REPLY: > I am aware of transformer supplies. I was referencing to switch-mode > supplies (transformer less). I believe they have isolation between > primary and secondary. > Radios using this type of supply should not need the "green" wire to > radio. It should go to the power supply itself as explained above. > > > 72 > Ron, wb1hga > > > > 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 09/04/2011 08:07 PM, Mark Bayern wrote:
> >>"I am aware of transformer supplies. I was referencing to switch-mode > supplies (transformer less). I believe they have isolation between > primary and secondary. > > Without a transformer? How are they getting any galvanic isolation? The > transformer-less switched mode power supplies I'm familiar are > most definitely _NOT_ isolated. I would like to see a design that was > isolate. not a bulky heavy transformer you would think of, The inverter stage converts DC, whether directly from the input or from the rectifier stage to AC by running it through a power oscillator, whose output transformer is very small with few windings at a very high frequency. (I understand the frequency is usually chosen to be above 20 kHz, to make it inaudible) The output voltage is OPTICALLY coupled to the input. The switching is implemented (to achieve high gain) MOSFET amplifier. MOSFETs are low on-resistance and a high current-handling capacity. Unless well designed, they can cause hash in AC line and be picked up by our ham radios. 72 Ron, wb1hga ______________________________________________________________ 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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>>"whose output transformer is very small with few windings ...
But that is not a transformer-less SMPS. It does have a transformer. I'm done with this discussion. Mark On Mon, Sep 5, 2011 at 10:05 AM, ron <[hidden email]> wrote: > On 09/04/2011 08:07 PM, Mark Bayern wrote: > >> >>"I am aware of transformer supplies. I was referencing to switch-mode >> supplies (transformer less). I believe they have isolation between >> primary and secondary. >> >> Without a transformer? How are they getting any galvanic isolation? The >> transformer-less switched mode power supplies I'm familiar are >> most definitely _NOT_ isolated. I would like to see a design that was >> isolate. >> > > > not a bulky heavy transformer you would think of, > The inverter stage converts DC, whether directly from the input or from the > rectifier stage to AC by running it through a power oscillator, whose > output transformer is very small with few windings at a very high frequency. > (I understand the frequency is usually chosen to be above 20 kHz, to make it > inaudible) The output voltage is OPTICALLY coupled to the input. The > switching is implemented (to achieve high gain) MOSFET amplifier. MOSFETs > are low on-resistance and a high current-handling capacity. > Unless well designed, they can cause hash in AC line and be picked up by > our ham radios. > > 72 > Ron, wb1hga > 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 9/5/2011 11:30 AM, Mark Bayern wrote:
>>> "whose output transformer is very small with few windings ... > > But that is not a transformer-less SMPS. It does have a transformer. No magic here. Aircraft AC power used to be 400 Hz, and may still be. It was[is] pretty simple. At 400 Hz, you need a lot less iron in alternators, motors, and transformers so they weigh a lot less. The concept has been around a long time. The turbine generators we used on airborne missions in the mid-60's were 400 Hz, both for weight and because turbines run at high RPM. Two troops could easily carry a 10 KVA turbine generator at a jog. Its diesel 50-60 Hz equivalent was mounted on a trailer and weighed about 1,500 lbs. The 400 Hz power supplies for the KWM-2A's, replacing the 516-F's, weighed about 3-4 lbs, including case. Nothing magic about 400 Hz either, that's just what was "engineering-ly convenient" in airplanes since it was generated by rotating machinery. Use an electronic switch at 25 KHz to create a square wave and you can use a transformer wound on a ferrite core ... even lighter ... but still a transformer. Good for us that power distribution stayed around 25-60 Hz. 25 KHz would have radiated all over the place, and does from an SMPS -- right into your receiver. SAQ in Grimeton, Sweden was on 17.2 KHz and did pretty well on the transatlantic circuit. :-) If I ever make it to Scandinavia, that alternator is on my "must see" list. 73, Fred K6DGW - Northern California Contest Club - CU in the 2011 Cal QSO Party 1-2 Oct 2011 - www.cqp.org ______________________________________________________________ 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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