These are guesses from the ignorant here; bad breaker (I've bought new duds before) or something back feeding into it???
----- Original Message ----- From: "Gene Heskett" <ghesk...@wdtv.com> To: emc-users@lists.sourceforge.net Sent: Tuesday, February 2, 2016 7:14:00 PM Subject: Re: [Emc-users] Odd SSR behaviour? On Monday 01 February 2016 19:09:51 Gene Heskett wrote: > On Monday 01 February 2016 17:49:01 John Kasunich wrote: > > On Mon, Feb 1, 2016, at 05:31 PM, Gene Heskett wrote: > > > Greetings; > > > > > > Those of you reading the mail know I made a soft start circuit for > > > the spindle PSU. > > > > > > It basically consists of two SSR's in series, the first one being > > > the main switch that enables AC power to reach the transformer by > > > way of a 51 Ohm 200 watt inrush limiting resistor. And that after > > > the filters are charged, nominally 10 seconds, a second SSR is > > > fired to short that resistor, allowing the supply to make full > > > output. Controlled by a couple timers driven by the > > > motion.machine_is_on signal. > > > > > > I had set the timers for a fairly speedy off, with the SSR across > > > te resistor being the first one turned off if I unclicked the 2nd > > > button, followed 5 seconds later by the first SSR being shut down. > > > Sort of a soft stop I guess. > > > > > > But today in playing with the pyvcp-pannel, I turned it off with > > > the 2nd button, and the 20 amp breaker I had put back in the > > > service to replace the ill eagle 30 amp dropped instantly. And > > > repeated everytime I stopped it with that button, 100% of the > > > time. > > > > > > I cannot imagine where a momentary short might be. So I piddled > > > with the setp's in the hal file so the softstart SSR was left on > > > for about 5 seconds, but the main SSR was disabled in about .5 > > > seconds, so that main power was disabled before the soft-start SSR > > > was disabled. > > > > > > Now its not tripping the breaker, which is cool. But the question > > > is, why did it trip 100% of the time before I did that? > > > > > > Other than an SSR surge internal breakdown to the case & sink, I > > > cannot come up with a valid reason for that behaviour. > > > > These have metal baseplates? > > Yes, bolted to the case, more for solid mounting than any need for a > heat sink. No detectable heat. > > > Connected to grounded sinks? You > > could rule out a breakdown to sink if you temporarily insulated the > > sinks from ground and went back to the old configuration. A single > > breaker trip with the sinks floating would tend to rule out that > > possibility. > > > > Is there ANY path from incoming line to neutral (or the other phase, > > if this is a 240V circuit) > > Upstream of the first SSR is where the switcher supplies for the axis > motors are fed. They come on with the strip switch. Nothing beyond > the SSR's except the transformers, which are identical, 4 of them with > primaries paralleled, and each secondary has its own rectifier and > filter bank, which are then connected in 2 in series and 2 sets of > that paralleled to double the available voltage and double the > available current. Available DC is in the 126 volt range, available > current on a 50% duty cycle is about 20-25 amps. Jon's PWM servo is > the driver, set for about a 15 amp current limit. The servo amp is > the only load and it would normally be disabled, drawing essentially > zero current when the spindle is stopped. > > > that doesn't go through the transformer? > > If the answer is no (it seems that way from your description), and > > the fault current isn't flowing thru the case of the SSR, then it > > must be flowing thru the transformer. The only way the transformer > > should draw that kind of current is for a cycle or two at startup, > > or if the core saturates due to a large DC component. Is it > > possible that one or both SSRs is only conducting on one half of the > > AC waveform? > > Both tally leds on the SSR's are nice & bright, and the same > brightness as its twin when both are enegized. I haven't looked at it > with a scope in about a month & then I could just barely discern the > cross-over zero but had to really look close. > > It appears I have solved the breaker tripping, but I'd sure like to > know why. I have that "waiting for the other shoe to drop" feeling. > :( > No, not fixed. The other first shoe is dropping, repeatedly. And now I am bumfuzzled. I moved the monitors power cord to a socket that doesn't die when that breaker trips. So I can now watch things with a halmeter while I turn it off. Then I stretched the off times of the SSR driver timers, to 2.5 seconds and 5 seconds after I click on the 2nd from the left axis top row icon. The breaker trips milliseconds after I click on the icon, regardless of the off times set in the two timers. I can see the breaker is tripped, turn my head back to the monitor and the halmeters, and watch the signal to both ssr's stop a from a second to 3 later. I am NOT controlling power to the steppers, they come on and go off with a switch on a power strip that controls this whole box full of stuff. I do not see the spindle motor jump, primarily because when the spindle is stopped, its completely stopped, disabled and has to have the initial bootup sequence generated by the boot module before it is re-enabled and capable of driving the spindle, so thats out. I do not hear or see the steppers take a step, I even felt the Z drive coupleing, not a twitch. This whole thing, sitting idle, draws less than 3 amps, 95% of which would be the steppers on half power, 2.65 amps I measured once with an amprobe, they are just holding position, its a 20 amp breaker. What the heck is tripping it? Since it is not coincident with turning off an ssr, I think that rules out flaky ssr's. If I had an analog amprobe I might see the needle twitch, but both of mine are digital, zero chance of seeing a surge that short. So, whats the next SWAG everybody? 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> ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. 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