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Dr. Garbanzo posted:I liked it when they did a stack of power upgrades at work and wired the phases backwards for the woodwork rooms. Backwards spinning machinery for days including the table saw Yup. Any three-phase motor, induction or synchronous, can have its direction reversed by swapping any two of the three phases of AC power going to the motor's stator (those are the magnetic coils that don't move). At work we have phase-angle meters for both high (>600V) and low (<=600V) systems. Despite this, we always do a "bump check" of any rotating equipment that is being comissioned. When you "bump" you close and immediately open the circuit breaker to the motor. This makes sure that:
Ideally you do this without the motor coupled to the load it's driving for optimal safety. If you have a big load like a ball mill (giant metal cylinder filled with literal cannonballs to smash up minerals) you'll have couplings and a gearbox in there. This is for big motors larger than, say, 1000HP that aren't off-the-shelf and have to be individually built. Despite all the best engineering, it's still generally a 50-50 shot. For a low voltage motor it can take a couple of minutes to isolate, LO/TO and swap the power leads. For medium voltage it could take an hour for isolation, grounding, LO/TO, and work depending on how well insulated the connections are - removing and re-installing insulation and stress relief cones. Three-Phase fucked around with this message at 21:25 on Jan 21, 2018 |
# ? Jan 21, 2018 21:22 |
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# ? May 14, 2024 03:29 |
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Wait. That can actually happen? I thought it was a joke. Oops. Learned something new, though!
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# ? Jan 21, 2018 21:26 |
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it happens all the time
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# ? Jan 21, 2018 21:37 |
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The worst-case problem isn't if you have motors where the phases are swapped, but if you have something like a generator that isn't phased correctly. If you think you are synchronized and connect a generator to a powerline out of phase, it's like taking two 9V batteries and connecting them positive-negative-positive-negative except potentially a lot more spectacular. Synchronizing a generator is a lot like "DJing electricity". If you want to mix between two tracks at one of those techno beep-boop-beep music clubs, you need to match the following:
For a generator:
If any of those are not within reasonable tolerance and you close the generator breakers you're going to have an extremely bad time. Nowadays synchronizing is controlled by a relay, and a lot of times there are even back up "sync check" relays because you can't afford to screw this up and destroy a multi-million dollar generator. But in the old days synchronization was "DJed" by hand. Three-Phase fucked around with this message at 21:58 on Jan 21, 2018 |
# ? Jan 21, 2018 21:55 |
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# ? Jan 21, 2018 22:02 |
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How much do you need for a fish and chips? Are you drinking it or something?
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# ? Jan 21, 2018 23:02 |
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Drape Culture posted:How much do you need for a fish and chips? Are you drinking it or something? Restaurants usually operate on razor-thin margins, so of course if they can save 50% on vinegar by using malt-flavored industrial 20% acetic acid solution instead of brewed/fermented malt vinegar, they'll do it.
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# ? Jan 21, 2018 23:05 |
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Drape Culture posted:How much do you need for a fish and chips? Are you drinking it or something? https://www.youtube.com/watch?v=642x2Y3Zla0
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# ? Jan 21, 2018 23:38 |
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whoa my comment is up to 1,6K likes I had forgotten about that one
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# ? Jan 21, 2018 23:45 |
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https://www.youtube.com/watch?v=Zu9fcLSEums I'm assuming that the first annunciator that starts flashing is indicating some kind of problem developing with the power grid connection before the control room goes dark.
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# ? Jan 22, 2018 00:34 |
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Best part about the table saw being hooked up backwards is the arbor nut that holds the blade on only really works and remains tight if the saw is spinning the correct way. It only took the guy 5 minutes to fix it in the end as well
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# ? Jan 22, 2018 00:39 |
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Three-Phase posted:https://www.youtube.com/watch?v=Zu9fcLSEums Hmm will the turbines have enough inertia to keep the cooling pumps going before the diesel generators kick in? Maybe someone should test that
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# ? Jan 22, 2018 01:08 |
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^^^ Tom Scott videos are pretty good and he has done work on other channels. The amount of effort he goes through is pretty drat high as he is always on location, does as heap of takes until he gets it right in a single long shot, like the one where he demonstrates a semi-forgotten 3D TV method on a 2D screen, talking and driving up and down a long musical road. So he can't get "lazy" with info-graphics.Three-Phase posted:https://www.youtube.com/watch?v=Zu9fcLSEums Every alarm bell going off doesn't seem to be all that useful unless you are looking to wake up the dead.
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# ? Jan 22, 2018 01:14 |
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oohhboy posted:Every alarm bell going off doesn't seem to be all that useful unless you are looking to wake up the dead. I could easily do a whole thread on alarm management, that's a thing nowadays. Part of the problem is that with modern DCS/SCADA (Distributed Control System or Supervisory Control And Data Aquisition, the computer networks that run modern plants) it's easy to make all kinds of alarms for everything. You can also have problems with alarms. For example, you have a huge pump that you do a routine shutdown on. The pump shuts off. No problem, no emergency. Suddenly the alarms start coming in: code:
Or you have a screen with some alarm that's flashing, and has been flashing for months because the sensor somewhere in the field is broken and the operators just start ignoring it and nobody has went and fixed it. (In fact in plants a lot of times a very small number of bad sensors, like a number of sensors you can count on your hands, can cause more than 90% of the alarm activation that operators have to deal with.) Or when something happens that upsets the processes at a plant (like a power plant, oil refinery, water treatment plant) and suddenly the operator has alarms blaring and literally hundreds of different alarms coming into his computer and he has to try and figure out both a "big picture" of what's going on, and find a way to start working through all the different alarms. It's crazy stuff and has some really serious consequences. Ooh I'd hate to be the insurance adjuster for that... Three-Phase fucked around with this message at 02:13 on Jan 22, 2018 |
# ? Jan 22, 2018 02:08 |
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Three-Phase posted:
She was a little windy in The Netherlands the other day. https://i.imgur.com/gEmJ3T5.mp4
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# ? Jan 22, 2018 02:31 |
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GotLag posted:Substituting a ~20% acetic acid solution with a ~20% acetic acid solution? Scandalous! 4%. 20% would be somewhat unpleasant.
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# ? Jan 22, 2018 02:31 |
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All this pump chat reminded me of a job I went to a few years back. An electric fire pump had been installed in a vault below the building’s parking lot. It drew water from an adjacent tank. IIRC the pump was supplied by 480v 3 phase powering a 50 hp motor (could be wrong, definitely not a electrician). The call from the building owner was as follows. Owner “Hey we had been hearing this low rumbling for the past few hours, and suddenly the whole building shook like a bomb” Me “Ok? Did it set off your fire system?” Owner “not that we know of, I think it just blew up, we have the fire dept here and they say we need you to come.” Turns out the pump had kicked on and sprung a leak on the discharge piping filling the vault with water. The dual sump pumps to keep the pit dry had been probably dead for years since no one had looked in the pit for 7 years! Anywho so the leak filled the vault up till the pump was completely submerged. Then the boom happened. The electrician told me that the pump had experienced either a phase loss, or phase reversal while under full speed. This caused the motor to shred itself? It was a mess is all I know. We ended up supplying an entire new pump, motor, and controller; right back into the same old pit. At least it gets looked at more frequently than every 7 years but drat what a dumb place to put an electric motor.
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# ? Jan 22, 2018 02:55 |
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Three-Phase posted:I could easily do a whole thread on alarm management, that's a thing nowadays. Go ahead on post more. That was a very good taste. I did some light reading on the matter mostly in regards to crew management in aircraft and they have come a long way from defcon 1 on any error or alarm. UI is still pretty terrible pass basic information. Not sure of current GPS units but programming one was like setting the timer on a VCR and because it's aircraft equipment you had to be certified to use each model as they didn't have common controls even within the same company. Then there is the ICU beeping killing people.
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# ? Jan 22, 2018 03:22 |
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SpaceCadetBob posted:All this pump chat reminded me of a job I went to a few years back. One important thing about fire pump motors - they basically have no protection. For all electrical equipment except fire pumps, you need to shut down the system to protect the conductors and equipment. But the idea with a fire water pump is that it must run to protect the building and personnel. Some military equipment has a similar "battle short" setting. If you're in a ship during a battle, you don't want to have the bilge pump motors keeping your ship afloat tripping off. You're saying "I'm willing to risk damaging the motor and equipment to prevent a much more serious problem." Same thing if a building's on fire. "Well, the building burned down, and we're removing bodies, but hey the fire pump wasn't damaged when it overloaded!" The circuit breaker, fuses, or combination that protect the water pump have to be rated to carry the locked rotor current of the motor. That's the current that would flow into the motor if the rotor was physically prevented from spinning. Normally after a short period of locked rotor fuses will blow or breakers will trip to protect the equipment. (There is a time delay at that current level because that's what a motor sees momentarily when it's stopped and suddenly switched on and isn't spinning.) So a motor that would normally have, say, a 100A molded-case breaker would now have a 400A breaker "protecting" it. That additional current allowed might have contributed to the "boom". A phase loss means one of the three phases going to the motor suddenly opens up and supplies no current. Unless the motor is minimally loaded, this causes a serious overload on the other two phases that are trying to keep the motor spinning. If it's not interrupted, the motor will burn out. This is also why you have to be very careful if you protect a motor using fuses that could blow separately rather than a device like a breaker where all phases open simultaneously. I worked on a 4160V motor starter where the fuses had metal pins that sprang out from the fuse when they blew. That pin (or pins) would slam against a fiberglass plate, trip a switch, and open the power contactor that fed power to the fuses. That way the motor wouldn't run on single phase. Not sure how reliable that sort of thing was, a modern protective system would measure the current in each phase and trip if there was an imbalance. (Even an imbalance in current or voltage between the phases, not just an open circuit, is very bad for motors.) Fuses were about the size of a Pringles can. A phase reversal means that instead of CBA it's now running ABC - if the motor is spinning full-bore and suddenly it tries spinning the other way you're going to get a nasty current surge. Normally this would trip the protection, but again, it's a fire pump motor. I'm not sure how a phase reversal would occur when it's running by accident for a pump that should only run in one direction. Bi-directional applications using three-phase motors, like for a trolley crane, could see a phase reversal if they were rapidly changed direction by the operator - I think they have electrial and mechanical interlocks to prevent that. Like instantly shifting your car from "D" to "R" at 60MPH. Three-Phase fucked around with this message at 03:53 on Jan 22, 2018 |
# ? Jan 22, 2018 03:43 |
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Sorry if this was posted somewhere in the thread but it's an absolute classic https://www.youtube.com/watch?v=XKZUFu97vus
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# ? Jan 22, 2018 04:27 |
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oohhboy posted:^^^ Tom Scott videos are pretty good and he has done work on other channels. The amount of effort he goes through is pretty drat high as he is always on location, does as heap of takes until he gets it right in a single long shot, like the one where he demonstrates a semi-forgotten 3D TV method on a 2D screen, talking and driving up and down a long musical road. So he can't get "lazy" with info-graphics. I wish someone would buy him a shirt that fits him though
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# ? Jan 22, 2018 04:34 |
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The Lone Badger posted:4%. 20% would be somewhat unpleasant. lol if you don’t season with reagent grade glacial acetic acid.
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# ? Jan 22, 2018 04:36 |
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Three-Phase posted:But the problem is the pump was shut down. None of those alarms make any sense (all of those would be part of a normal shutdown) and will just distract the operators. That sort of mistake is probably the more egregious configuration errors but it happens. This is a *major* problem in the healthcare field. This whole longform about a massive overdose of antibiotics and the contribution of lovely UI to the chain of events that led to it is worth a read: https://medium.com/backchannel/how-technology-led-a-hospital-to-give-a-patient-38-times-his-dosage-ded7b3688558 But on this specific issue: quote:In the face of growing nationwide concern about alert fatigue, Barbara Drew, the UCSF researcher, set out to quantify the magnitude of the problem. For a full month in early 2013, she and her colleagues electronically tapped into the bedside cardiac alarms in UCSF’s five intensive care units, which monitored an average of 66 patients each day. Mind you, this is just the bedside cardiac monitor, which follows the patient’s EKG, heart rate, blood pressure, respiratory rate, and oxygen saturation. It does not include the IV machine alarms, mechanical ventilator alarms, bed exit alarms, or nurse call bell. Nor does it include any of the alerts in the computer system, such as the Septra overdose alert that Jenny Lucca overlooked.
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# ? Jan 22, 2018 04:37 |
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Serak posted:I wish someone would buy him a shirt that fits him though https://www.youtube.com/watch?v=zYd_8-Ps_kw&t=35s
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# ? Jan 22, 2018 04:38 |
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Worker burned after jackhammering into electricity line in North Hobart street, police say http://www.abc.net.au/news/2018-01-22/high-voltage-line-suspected-in-road-works-accident/9349498 Witnesses heard what was described as at least two "pops" or "explosions". The incident happened outside Phil Hoskinson's business. "It was really loud," he said. "It wasn't like a bomb explosion — more like a fume explosion, a build up of gases. "We just saw the big plume of smoke, grabbed the fire extinguisher, and the bloke was there on our doorstep." He said the worker had managed to get himself up out of the hole but was on fire. "We've dragged him into the workshop and he's stopped breathing for a while, so we just made him comfortable and rolled him on to his side," Mr Hoskinson said.
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# ? Jan 22, 2018 06:07 |
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Three-Phase posted:My theory is it's a delta-wye motor starter (starts the motor in this case with 347V across the windings, then switches once it's started to the full 600V) but if the different contact sets are operated at the wrong time you can cause a dead-short. Interesting, most delta-wye starters I've seen here go in the opposite direction. Say you have a 7.5kw 3ph motor which is usually the biggest size you can run on a consumer hookup and what might come with an electric log splitter. Such a motor is rated for 400-690V and it starts off in the 690V mode (Delta), being fed 400V, then switched to 400V mode (Wye) as the motor speeds up. Such motors are also used in industry but there I understand they just direct start them at 690V. Papa Emeritus III posted:Wait. That can actually happen? I thought it was a joke. When I added more outlets in my garage the electrican had me start up the table saw to see everything was wired in the "right" direction. Though there is no right or wrong phase arrangement, more that it's in line with what my machines were already hooked up for. His Divine Shadow fucked around with this message at 08:27 on Jan 22, 2018 |
# ? Jan 22, 2018 08:24 |
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Serak posted:I wish someone would buy him a shirt that fits him though https://www.youtube.com/watch?v=p4SoSBo_nsI
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# ? Jan 22, 2018 16:13 |
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oohhboy posted:^^^ Tom Scott videos are pretty good and he has done work on other channels. The amount of effort he goes through is pretty drat high as he is always on location, does as heap of takes until he gets it right in a single long shot, like the one where he demonstrates a semi-forgotten 3D TV method on a 2D screen, talking and driving up and down a long musical road. So he can't get "lazy" with info-graphics. His content is great but I absolutely can't stand the cadence of his speech. He's got that dumb youtube voice
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# ? Jan 22, 2018 16:30 |
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I think he's got one of the more listenable voices of many youtubers. There are plenty others that I have a much harder time listening to even if their content is interesting. (Dave from EEVblog comes to mind)
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# ? Jan 22, 2018 16:46 |
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HDS - that’s interesting! I had never heard of that but I did some searching and did see special motors that were configured for “low voltage start/high voltage run” or “high voltage start/low voltage run”.
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# ? Jan 22, 2018 17:14 |
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Platystemon posted:lol if you don’t season with reagent grade glacial acetic acid. Harder to get in small amounts than you might expect. My bottle, which I use to fumigate beehive equipment, keeps showing up in OSHA areas as my partner tries to helpfully tidy. Right next to actual condiments is not an appropriate storage location for glacial acetic acid.
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# ? Jan 22, 2018 17:32 |
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POOL IS CLOSED posted:Harder to get in small amounts than you might expect. Have you considered putting a big old skull on it?
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# ? Jan 22, 2018 17:37 |
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Collateral Damage posted:I think he's got one of the more listenable voices of many youtubers. There are plenty others that I have a much harder time listening to even if their content is interesting. (Dave from EEVblog comes to mind) I genuinely wish that youtube had a pitchshift filter to get the frequency of his voice down to human-audible levels. Bats lcan hear him, but have little interested in electronics.
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# ? Jan 22, 2018 17:53 |
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Volcott posted:Have you considered putting a big old skull on it? I think skulls are contraindicated as signage here because of the alarming variety of skull themed baking tools we own. I stored it in a mini fridge with some hazard tape on the bottle in the end.
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# ? Jan 22, 2018 17:59 |
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POOL IS CLOSED posted:I think skulls are contraindicated as signage here because of the alarming variety of skull themed baking tools we own. I stored it in a mini fridge with some hazard tape on the bottle in the end. Mr. Yuk
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# ? Jan 22, 2018 18:02 |
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Messing with the new guy https://i.imgur.com/7Ai1ghN.mp4
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# ? Jan 22, 2018 18:28 |
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Three-Phase posted:HDS - that’s interesting! I had never heard of that but I did some searching and did see special motors that were configured for “low voltage start/high voltage run” or “high voltage start/low voltage run”. As I understand it these are normal 3ph motors that can be run normally in either configuration. As it was explained to me, when you put regular domestic 400V 3ph over the windings in 690V mode, the motor runs slower and uses less amps, so it's easier on the fuses during startup phase when it would otherwise draw most, then it switches to 400V mode and it runs normally. The control logic is all in a separate Y-D unit and can be fitted to any 400/690V 3ph motor. Most motors here tend to be 230/400V and are rated 5kw and less, those are run in 400V and direct started, like on my table saw and band saw (2.2 and 2.5kw motors). They can be reconfigured for 230V (Delta) if you are in Norway, or North America. And as I understand it 400/690 motors are the same, just a step bigger. Also I mixed up Delta and Wye in my first example, in a 400/690 motor 400V is Delta. I am so used to thinking of 400V as Wye. His Divine Shadow fucked around with this message at 18:30 on Jan 22, 2018 |
# ? Jan 22, 2018 18:28 |
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POOL IS CLOSED posted:I think skulls are contraindicated as signage here because of the alarming variety of skull themed baking tools we own. I stored it in a mini fridge with some hazard tape on the bottle in the end. Glancing at an SDS, it should actually have a corrosive pictogram: Which I'll take as an opportunity to repost this comedy option:
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# ? Jan 22, 2018 18:48 |
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I'm going to print out both for the chaos option, thanks. (Okay one goes on the liquor cabinet.)
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# ? Jan 22, 2018 18:52 |
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# ? May 14, 2024 03:29 |
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zakharov posted:Sorry if this was posted somewhere in the thread but it's an absolute classic Yeah, that one's been around and spliced and over to the main house and spliced and painted over the old cord. So good.
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# ? Jan 22, 2018 19:27 |