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I'm looking for a second opinion here. I'm working on a repair technician course for a piece of equipment that is dual-fed 480VAC and 230VAC, each three phase. Initially, there were all over me to make sure the students knew all about arc flash hazards. Then when I pushed them hard enough on getting the right PPE in, they changed their tune and decided to install some magic fuses on the 480 line that bring the hazard down to class zero. Now they claim it's all business as usual. I just need to review Lock-Out Tag-Out. Can these fuses really reduce the hazard? I'm more a mechanical guy than electrical, I have trouble making sense of the NFPA standard.
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Sep 14, 2011 00:40
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| # ¿ May 7, 2024 11:23 |
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KaiserBen posted:Short answer: No. Long answer: Hell no. That's what I suspected. The only real explanation I had was that the clearing time of these fuses was fast enough that it all didn't matter. Basically, "It's cool bro."
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Sep 14, 2011 02:18
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Simply Perfect!
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Feb 11, 2012 17:41
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Three-Phase posted:As an aside: I was joking around with co-workers about how cool it would be to have an ordering option to include an ABB engineer with the larger drives. I work with a guy who used to do ABB field service. I'd be happy to put him in a box and ship him out to you. (He's really not that bad, just tells some bad jokes sometimes.)
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Feb 18, 2012 15:09
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"So there's the new Megadrive... wait, who the hell's that guy?"
"Oh, he's Paul. You add an '-ENG' to the end of the part number, and they also ship a engineer in that other crate."
"Hallo! Ich kam mit dem Hochspannungs-Laufwerk!"
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The low voltage compartment also works well as a place to keep your beer while racking a breaker.
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Apr 7, 2012 12:49
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I was going to make a post saying that the bow-tie was part of the necessary PPE, but you beat me to it and with a good reason even. I work on printers myself, and would agree that ties do not belong anywhere near a roll-feed printer.
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Apr 9, 2012 22:52
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I was talking to a guy at work about PPE requirements. He told me that NFPA 70E only applied to facility wiring, not to appliance wiring (i.e. anything with a UL sticker on it). I know this guy will make stuff up just to show how "smart" he is. Is basis in reality for this?
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May 16, 2012 01:37
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Three-Phase posted:Are you talking about equipment that would be directly wired into an electrical system at a lower voltage (<600V) that still bears the UL sticker? Are you wiring up live, or testing live equipment with protective covers removed? This is 480 VAC equipment, testing operation and verifying input voltage, etc. Also, whoever decided to put 24V, 120V, and 480V all in the same cabinet in this equipment was a moron. They probably also got a pat on the back for saving the company money.
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May 16, 2012 22:42
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It seems like it would be dangerous to put a sign on your truck saying "Yep, its grounded!" It would create a false sense of security if you ever forgot to take the sign down.
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Aug 29, 2012 00:43
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grover posted:Cross-posting from the generator thread: Cool stuff. Does my laptop charger care much about these waveform abnormalities?
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Nov 7, 2012 00:44
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I'm sorry 911 dispatcher, but I can't hear you over my factory exploding.
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Feb 20, 2013 23:17
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But:quote:See how the arc flash is minimum, as the ground fault current is just 5 A Basically, it's cool bro, don't worry about it.
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May 19, 2013 19:38
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Sir, I can't hear you over the explosions and fire alarm. Could you please repeat the nature of your emergency?
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Jun 29, 2013 00:52
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https://www.youtube.com/watch?v=TXtiHJKClEw This is a video from a different control room showing a simulated scram. They use the ding sound from The Price is Right, nothing like the cacophonie in the other video.
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Jul 7, 2013 15:05
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 Get three trefoils to trigger the meltdown jackpot.
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Jul 7, 2013 16:52
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It could have been a brown-out. A brown-out is when the voltage supplied to your home is lower than normal. Think of it like turning down a dimmer switch, but on your whole neighborhood. Lights might be dimmer, and other things will behave strangely. Electronics probably will either work normally, or not work at all.
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Jul 11, 2013 00:33
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Even if your electronics are on the same circuit, their power supplies will have different sensitivities to the brown-out. Really cheap power supplies will put out a correspondingly lower voltage. Nicer ones will notice that they can't put out their normal voltage and will switch off entirely. Others will still be able to put out their full voltage and will happily chug along.
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Jul 11, 2013 01:18
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One of my coworkers used to work for ABB. He was visiting customer site in South America, and was walking down some sort of hallway, and one side had a chain link fence for a wall. Something didn't quite feel right, and realized on the other side of that fence, within a foot or two, was an un-insulated high voltage "bus duct".
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Jul 12, 2013 20:09
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What about solar and/or wind generation that allows for sending power back into the grid?
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Aug 1, 2013 00:22
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White House calls for increased spending on the electircal grid: http://hosted.ap.org/dynamic/stories/U/US_OBAMA_ELECTRIC_GRID?SITE=AP&SECTION=HOME&TEMPLATE=DEFAULT Where should the spending be targeted? Is it a matter of like-for-like replacement of old poo poo, adding capacity, or something else?
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Aug 13, 2013 17:48
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They make CF cards that are at faster than SD.  It isn't a media bandwidth issue. It could be a interface bandwidth issue, or they just want you to buy a more expensive product to get more features. I tried to find out what speed they supported on the Power Visa, but it doesn't say. I did notice they tried to say you could use only Dranetz brand CF cards. Yeah, right. Bosch-Rexroth tries to do the same thing, and even uses a messed up partitioning scheme to force you into it. I fixed that with dd. No more $1500 replacement CF cards.
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Sep 22, 2013 14:44
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I'd imagine you must have to. Some parts take days to machine. You can do damage to a part if the spindle were to just spin down on its own, like if you are tapping threads, or if the axes aren't held in place without power, and they just drop.
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Oct 16, 2013 01:53
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I think Tons of Cooling has BTU beat as far as archaic units go.
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Dec 24, 2013 13:43
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Call the local fire department / fire marshal / building inspector and have them do an inspection. They will have their own CO meters. They also probably have better access to the local permits, and if they really don't have an occupancy permit, will know immediately.
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Mar 19, 2014 11:37
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Is the frequency of the grid still adjusted at night to ensure a correct daily average for clocks that use the 60 Hz (or 50 Hz) signal as a reference? Timekeeping seems pretty related to industrial electricity.
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Sep 2, 2016 20:26
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