On Sunday 25 March 2018 21:58:58 John Kasunich wrote: > On Sun, Mar 25, 2018, at 8:29 PM, Gene Heskett wrote: > > > On Sat, Mar 24, 2018, at 5:54 PM, a k wrote: > > > > I measure supply 120 v ac. > > > > Thats another problem, the std line voltage has been 127 volts for > > several decades. I would at least compare what this one reads > > against a known good meter, because either your building wiring is > > wonkie, or that meter belongs in the trashbin, thats about a 5% > > error. > > I beg to differ on that. 127V is NOT the standard and has never been. > It has been since the 70's John. I could probably find it in my copy of the NEC, and its old, 1996 issue. And then again, maybe not. The NEC sets voltage classes, but is far more concerned with the currents. Some time in the mid 1970's it had been 122 volts for a while, before that 117, and in nominally 1950 its was practice at 112 volts. Then circa 1980 it was raised to 127 and still is. That change wound up costing Nebraska ETV a piece of money because several of the states transmitters had been provisioned with Sola Constant voltage transformers of several tons of mass, but the increased voltage, combined with the summer heat resulted in the grand and glorious failures of at least 3 out of all the 7 that were equipted with GE UHF transmitters.
For KXNE-TV it turned out to be a blessing because it, when by-passed, removed the sola's inductance in between the transmitter and the power line, getting rid of a highly visible hum bar pattern caused by the slow diode switching in the 3 phase 35kv rated high voltage power supplies for the klystron amplifiers. It choked all the diode recovery spikes back into the building causeing blown light bulbs and small fuses. I stuck a scope probe in a wall socket and was amazed to see those voltage spikes topping out at over 3 kilovolts, sitting on the sola's distorted sine wave. With the sola burned up and bypassed, I never had another blown fuse or light bulb until a Heineman circuit breaker single phased the main water pump in the middle of the day. My hand had only about 2 feet to move to hit the beam power off button when I recognized the sound of a single phased 20hp pump motor, but by the time my hand had arrived at the button, it was dark, there was a boom as the klystron burned a hole in the bucket and filled with 30% pure water and ethylene glycol. That boom was $126k$. Part of the boom was the building entrance breaker clearing, a 1200A/phase breaker. By the time I had sourced another breaker, Larry had come up with a monitoring circuit so if any thing ever happened to that breaker again, the GE AK-225 beam power breaker was tripped and the system crowbarred to protect the tube. Anyway thats history, and here in WV I have 126.5 to 127 coming out of any wall plug here at the coyote.den. And I've been looking at that since about 1984. Haveing asked the local redi-kilowatt people, they've all replied that it was +- about a half a volt of 127. But I haven't managed to find it anyplace in my old copy of the NEC. So I can't say its a std. I suppose it could be different in different regions of the country. I do know that the first thing I did to this old GE transmitter which was designed for 110 volt supplies, was to install 3 phase power stats at several locations in order to get the filament voltages down to the tubes design voltages, or if the tube was fresh, as much as 10% low. That cut my budget for tubes by about 90%. > The standard is 120V, with a tolerance of +/-5% at the service > entrance and +5/-10% at the load. See this document: > https://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/ener >gystatus/powerquality/voltage_tolerance.pdf Or any number of other > specs and standards. Or simply look at the nameplate of any appliance > or even the top of a light bulb. > > If you have 127V at your house, you are actually a hair above the +5% > tolerance. Maybe your local power company has set the transformer > taps a bit high to allow for voltage drop at the far end of the line, > and you are stuck with it because you are near the transformer... -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
