On Monday 07 December 2015 00:01:20 Jon Elson wrote: > On 12/06/2015 10:42 PM, Gene Heskett wrote: > > On Sunday 06 December 2015 22:57:52 Rafael wrote: > >> On 12/06/2015 07:25 PM, Gene Heskett wrote: > >>> Greetings all; > >>> > >>> Before tv's lost their crt's, there was a component in the power > >>> inlet circuit that had a very high negative temp coefficient, > >>> which was used to create a high voltage drop when it was cold, > >>> which in turn forced the first few seconds of its power draw after > >>> being turned on, thru the degaussing coils wrapped around the crt > >>> in order to demagnetise it. > >>> > >>> That voltage drop heated it, and it got hot enough to get down to > >>> just a couple of ohms, which was not enough to overcome the MOV in > >>> series with the coils. This also allowed the tv itself to be > >>> soft-started, and it worked so well that it was often the major > >>> part failure in the tv for the first 3 or 4 years. > >>> > >>> About 3 or 4 of those, wired in parallel, would also serve as an > >>> inrush limiter when I turn on the power supply for my G0704 mill. > >>> But the parts houses we had locally have all evaporated. I just > >>> checked a couple surplus places without finding any of those > >>> critters. > >>> > >>> Does anyone have a suggestion as to where a small handfull of > >>> these could be sourced? Usually bare, they look like a graphite > >>> quarter coin with a lead wire soldered to the middle of a silver > >>> plated dot in the middle of each face. Usually slightly thicker > >>> than a 'merican quarter. > >> > >> I think you are looking for NTC (Negative Temperature Coefficient). > >> Search brings back numerous links to choose from. However, there > >> are better solutions but cost a bit more of course. > > > > Yes, and contrary to a previous poster, the name isn't a Surgistor, > > but a "Thermistor" for the NTC component. > > Digi-Key has them, but maybe not in a current you want. > http://www.digikey.com/product-search/en/circuit-protection/inrush-cur >rent-limiters-icl/656273?k=ntc%20thermistor > > Here's more : > http://www.digikey.com/product-search/en/sensors-transducers/thermisto >rs-ntc/1966148?k=ntc%20thermistor > > Jon
Now that I've thought about it, since the loading is highly dependent on the spindle motors loading,so the draw can run from about 2.75 amps to perhaps 18 or so for locked rotor, at least a 6/1 ratio, the more I realize that is the wrong approach. Far more consistent would be a flat time delay, operated by one of the other supplies in that box, rigged to put a 8 ohm 20 watt R in series with the line in, for perhaps 1/2 second after power on. That should cut the inrush by at least 50% of its peak amperage. Most time delays I can find are more than 1 second, least I found tonight was 6 seconds, and I don't have enough of those 8 ohm 20 watters to last that long. I may, when things slow a bit, see about building my own time delay in hal. Maybe even tie it to the charge pump so I can control the power to the mill with LCNC. Use a time delay hal module to gate the charge pump, first to power it up, then half a second later to close the relay and short the current limiter. The switched charge pump is controlling the vacuum cleaner (older Bucket Max) just fine. And I still have quite a few pins on the 2nd BoB to do that with yet. Thanks Jon. 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> ------------------------------------------------------------------------------ Go from Idea to Many App Stores Faster with Intel(R) XDK Give your users amazing mobile app experiences with Intel(R) XDK. Use one codebase in this all-in-one HTML5 development environment. Design, debug & build mobile apps & 2D/3D high-impact games for multiple OSs. http://pubads.g.doubleclick.net/gampad/clk?id=254741911&iu=/4140 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
