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Motronic posted:
i don't know much of anything about electronics in general but does this also apply for modern TVs? i've ran into a few different situations in the field where a TV was plugged into 240v on accident and used and continued to work fine even after the wiring was fixed and back to 120v. one time while doing a panel change my marking tape came off and the neutral for a circuit was landed on a breaker. killed their microwave and the kids Xbox power supply but the TV was fine. the other instance a homeowner decided to start tapping into random junction boxes to add a receptacle for his wall mount TV and ended up picking one that was 240...used his TV for weeks before we figured it out doing some other work for him.
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Jul 4, 2014 02:02
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crocodile posted:i don't know much of anything about electronics in general but does this also apply for modern TVs? i've ran into a few different situations in the field where a TV was plugged into 240v on accident and used and continued to work fine even after the wiring was fixed and back to 120v. one time while doing a panel change my marking tape came off and the neutral for a circuit was landed on a breaker. killed their microwave and the kids Xbox power supply but the TV was fine. the other instance a homeowner decided to start tapping into random junction boxes to add a receptacle for his wall mount TV and ended up picking one that was 240...used his TV for weeks before we figured it out doing some other work for him. Yeah, a lot of TVs use switched mode supplies. Just look at the back of it.....the rating plate will tell you what it will take for voltage/frequency.
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Jul 4, 2014 02:09
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Yeah, many active power factor correction power supplies will handle anything from, iirc, 90 to 264 volts without problems. Check the plate on the back, but it will probably say about the same thing. It is a side benefit of one of the major techniques for handling power factor correction. It also means 50/60Hz compatibility is built in, too.
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Jul 4, 2014 02:13
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Jul 4, 2014 03:03
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Motronic posted:Yeah, a lot of TVs use switched mode supplies. Just look at the back of it.....the rating plate will tell you what it will take for voltage/frequency. This. If the ratings plate says "100-240V 50-60Hz", then it will work in any plug in the world, with a prong adapter if necessary. Hey, copper pipes are good for grounding!  Also, the I've only red labeled NM I've ever seen like that had aluminum wires. 
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Jul 4, 2014 03:22
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 W H YEven if that's some kind of powered water shutoff from hell, it's making my nutsack shrink up into my abdomen.
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Jul 4, 2014 03:41
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On a similar topic, at my old place of work, one of our guys (definitely not an electrician) did a bunch of the wiring for our warehouse, and ended up making a bunch of outlets 3 phase which were not supposed to be. They functioned fine with most stuff, but the way we would occasionally discover one was 3 phase was by plugging either a circular saw or a vacuum in, at which point the motor would run ridiculously fast and burn out in a majestic puff of smoke. So, why didn't these outlets kill computers or phones or such? Do motors just suck up as much voltage as they are fed?
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Jul 4, 2014 03:56
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Slugworth posted:So, why didn't these outlets kill computers or phones or such? Do motors just suck up as much voltage as they are fed? Devices that use AC directly, especially devices that use a lot of power, don't have that kind of voltage converter.
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Jul 4, 2014 04:40
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Mizufusion posted:I am not a redwood expert, but a dawn redwood might work for you. They might not grow as tall as coast redwoods, and they don't have the same dark red bark, but I think they're still pretty. Unlike their relatives, they're actually deciduous trees, which may be a pro or a con depending on your viewpoint. I think it makes the foliage nicer because it's softer and brighter green, especially when the leaves are new. Wiki says "In cultivation, M. glyptostroboides is hardy to USDA Zone 5, making it hardy down to lows of -25°F (-32°C)." so right on the limit for my area, it can get colder but only a few days per year.
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Jul 4, 2014 05:14
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Slugworth posted:On a similar topic, at my old place of work, one of our guys (definitely not an electrician) did a bunch of the wiring for our warehouse, and ended up making a bunch of outlets 3 phase which were not supposed to be. They functioned fine with most stuff, but the way we would occasionally discover one was 3 phase was by plugging either a circular saw or a vacuum in, at which point the motor would run ridiculously fast and burn out in a majestic puff of smoke. They're not exactly three phase because they'd have to have four pin plugs for that but it sounds like the problematic ones were wired to one of the other two phases where it should have been neutral. They were most likely pushing 208v and be glad you don't work there anymore.
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Jul 4, 2014 05:24
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Motronic posted:I can't find any reasonable definition on google for what phase-phase is supposed to mean, so I really can't understand the meaning of your post. I think he's talking about split-phase ~220 (180 degrees) vs phase-to-phase ~208 off a delta/wye transformer (120 degrees), which shouldn't really make a difference.
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Jul 4, 2014 19:44
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Motronic posted:I can't find any reasonable definition on google for what phase-phase is supposed to mean, so I really can't understand the meaning of your post. No, I'm not part of the crowd who thinks you can have too much amps or some such, my concern with charging a phone off a stove plug or some such is not that it can supply too much power (I know that the device will use what it will use and not more) but that the power would be supplied in the wrong way. By phase-phase I mean like a US 3-wire dryer plug, two hots of 120V each, 180 degrees out of phase. I really don't know if a device that normally expects a single phase with a 240V hot side and a return would work or fail to, and if it fails, in what fashion, if it were supplied with two 120V hots. This is where my understanding of phases is shaky.
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Jul 5, 2014 00:39
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Red_October_7000 posted:I really don't know if a device that normally expects a single phase with a 240V hot side and a return would work or fail to, and if it fails, in what fashion, if it were supplied with two 120V hots. This is where my understanding of phases is shaky. Let's assume that you have two appliances and run 3 wires to each. In case one, you run a 240V hot, a neutrals, and ground. In case two, you run a 120V hot 1, 120V hot 2, and ground. In case 1, you get a 240V hot to neutral voltage at 60Hz. In case 2, you're still getting 240V at 60Hz measuring from hot 1 to hot 2, since the two are 180 degrees out of phase. The appliance doesn't know any different because it can't tell the difference between a bonafide neutral and hot2. The only case in which this is an issue is when the appliance has a neutral/ground bond, which it goddamn well shouldn't, throw that fucker out.
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Jul 5, 2014 03:00
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Tim Thomas posted:The only case in which this is an issue is when the appliance has a neutral/ground bond, which it goddamn well shouldn't, throw that fucker out. And that was NEVER acceptable and nothing was made that way to my knowledge. There are 240v US appliances that use a neutral for 120v portions of themselves, but that needs to be wired to a neutral, not a ground (I would not be at all surprised if people wired the neutral to the ground rather than rewiting outlets). If someone has wired it to a ground it will "work" but you've now violated the cardinal rule that there is exactly ONE place on a service where neutral bonds to ground. That place needs to be your first (or only) panel past the meter or a generator/solar transfer switch if it is placed before the panel. And NOWHERE else. Not at an appliance, not in an outbuilding with it's own panel. Just never, ever ever. E: Tim I know I'm saying things that you already know, just clarifying/expanding for others. Motronic fucked around with this message at 04:24 on Jul 5, 2014 |
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Jul 5, 2014 04:19
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Gromit posted:I used to work for the police in their digital forensics unit, and dropped in on the Kyoto police headquarters in Japan when there on holiday just to say hello. You should make a thread about being in digital forensics and your experiences.
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Jul 5, 2014 07:18
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Tim Thomas posted:Here's what you're missing: two 120V hots on a split phase system is the exact same as what you're thinking of as "single phase with a 240V hot and neutral". This is very simply where my understanding breaks down. Is there no qualitative difference between 240V derived from two 120V positives 180 degrees out of phase and 240V derived from a single phase, which is how I can only assume power is provided in countries where higher voltages are the norm?
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Jul 5, 2014 08:16
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Red_October_7000 posted:This is very simply where my understanding breaks down. Is there no qualitative difference between 240V derived from two 120V positives 180 degrees out of phase and 240V derived from a single phase, which is how I can only assume power is provided in countries where higher voltages are the norm? No difference whatsoever. You're likely thinking about this from the reference of the neutral coming off the split phase (two 120V hots 180 degrees out of phase). Thinking about this, this would be the equivalent of attaching one lead of your voltmeter to the neutral and then the other lead to one of the hots, then the other. Your meter will read 120V both times. Cool poo poo. Now move the lead of your voltmeter on your neutral to the other hot: it's now 240V. Your voltmeter has no idea that there's another neutral in the system! The appliance only knows about the wires it is attached to, and assumes one of the leads to be the reference (we'll call this the neutral, although it's not entirely correct to say so). Since the reference is moving around 120V at 60Hz out of phase to the other lead, the other lead is effectively doubled. Hence, 240V hot single phase. They're physically identical.
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Jul 5, 2014 12:42
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Red_October_7000 posted:This is very simply where my understanding breaks down. Is there no qualitative difference between 240V derived from two 120V positives 180 degrees out of phase and 240V derived from a single phase, which is how I can only assume power is provided in countries where higher voltages are the norm? In countries with typical 240V, you normally get 50 hz, instead of 60 hz. There's also different fusing requirements for circuits. Switch mode power supplies in many electronics will often handle it fine, if rated for the voltage difference (my PC's power supply is rated 100-240V, 50-60 hZ). Anything like a microwave, appliances with motors, stuff with heating elements, alarm clocks, etc, will not like the difference between 50 hz and 60 hz. But assuming you're dealing with only 60 hz, there's no difference to the equipment about two 180 degree 120V lines vs one 240V and one neutral. North America uses 60 hz; most of the rest of the world uses 50 hz. Adding to the fun, all of Japan uses 100 volts. Half uses 50 hz, half uses 60 hz. And much of Japan uses US style 2 prong polarized plugs.
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Jul 5, 2014 13:38
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the other thing is 240v single phase/split phase (logically equivalent to any 240 load) vs 208v pulled off two phases of a 3ph system. Those are somewhat different, and I have never found any reasonable explanation of how you can add two same-amplitude sines 120 degrees out of phase and get anything resembling a sine wave. I guess I just don't get that. How can an AC motor run smoothly off such a wonky not-sine wave? Heating/pure resistive loads, sure, all they care about is RMS voltage, but motors get pissed if you feed them non sinusoidal power.
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Jul 5, 2014 15:18
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kastein posted:Those are somewhat different, and I have never found any reasonable explanation of how you can add two same-amplitude sines 120 degrees out of phase and get anything resembling a sine wave. Sure looks like a sine wave to me:  The dark wave is the sum of the two lighter waves, one of which is 2pi/3 further along than the other.
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Jul 5, 2014 15:35
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Turns out, adding any number of sine waves of the same frequency will result in a sine wave. http://2000clicks.com/mathhelp/GeometryTrigEquivPhaseShift.aspx The special case where the amplitudes are equal, and 180 degrees out of phase resulting in total destructive interference is also a sine wave, with amplitude = 0.
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Jul 5, 2014 15:44
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Well hell, it sure didn't look like that when I did it last  I have no idea what I did.
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Jul 5, 2014 15:45
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So can you americans explain why you don't have 3-phase in residential dwellings. It's pretty much standard in scandinavia and I think germany too. Doesn't seem to be a technical limitation, unless there's something else different about american power systems than just the volts and hertz.
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Jul 5, 2014 19:18
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We don't need it? Some folks have 3-phase setups in their garages, and it's not difficult to get it installed if you want it, but what normal household needs are there that demand three-phase setups?
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Jul 5, 2014 19:27
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His Divine Shadow posted:So can you americans explain why you don't have 3-phase in residential dwellings. It's pretty much standard in scandinavia and I think germany too. Doesn't seem to be a technical limitation, unless there's something else different about american power systems than just the volts and hertz. Likely due to cost. When you have sprawling cities, you just have to run one phase of HV down each alley or out into the boonies then a cheaper single-phase transformer.
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Jul 5, 2014 19:40
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Leperflesh posted:We don't need it? Some folks have 3-phase setups in their garages, and it's not difficult to get it installed if you want it, but what normal household needs are there that demand three-phase setups? We run our stoves and heavy electricity gulping stuff like that on 3-phase so we do get use out of it regularly. And since starting to set up a garage workshop I became more aware or just how awesome it is, now I get access to 3-phase machinery which opens up a whole other range of equipment for me.
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Jul 5, 2014 19:41
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kastein posted:Well hell, it sure didn't look like that when I did it last
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Jul 5, 2014 20:09
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It's a combination of legacy and cost, which I guess comes down to cost. I've heard it said that one of the "nice" parts about Europe is that so much infrastructure was toast after World War II that the countries started with a clean sheet in many cases, so whatever the optimum of the time was pursued instead of trying to bandaid the existing infrastructure.
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Jul 5, 2014 20:35
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Zemyla posted:You probably added two sine waves with different frequencies.. I did something dumb, but not that dumb. Give me at least a little credit here, I do in fact realize that all 3 legs of a 3 phase power system are the same frequency.
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Jul 5, 2014 20:55
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The reasoning behind using single vs three-phase in the U.S. was because of the added cost of 3 phase transformers vs single phase, the fact that we are a large country and spread out, which would increase the costs; and that when we first started widespread electrical distribution, the majority of the electrical loads were resistive in nature and thus do not benefit from 3 phase current like AC motors do. It's definitely not cheap to have the power company put up a 3 phase transformer on your power pole, but it varies by area. The rates are also different, I think you pay a base minimum no matter how much you use. Of course rotary converters are very easy to make, not to mention VFDs and static converters.
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Jul 5, 2014 20:59
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What is the benefit of three phase? I always thought three phase was for sensitive machinery that needed more consistent amperage, in which DC power would be too bulky or something.
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Jul 5, 2014 22:14
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ijustam posted:What is the benefit of three phase? I always thought three phase was for sensitive machinery that needed more consistent amperage, in which DC power would be too bulky or something. Three phase isn't for "sensitive" machinery. It's just really good for running large motors efficiently. Bottom line, we'd be better off with a typically higher voltage supply to a residence, whether that's 240v outlets or 208v outlets (two phases of split phase or two phases of 3 phase). It would reduce the amperage required as well as make it easier to do things like run a simple water kettle in a meaningful way (notice they are quite popular in Europe but not so much in the US.......mine take like 5-10 minutes to boil a full pot of tap water). But this would require not only a re-thinking of the distribution side of the power grid, but a lot of home wiring, load centers, meters and mostly devices. That's a lot to overcome. I spec all of my datacenter stuff as 240 or 208 as available. Most times I'll use 30A 3 phase as feeders and peel them off in the rack in a PDU to get to the line voltage I need. I agree with Chauncey here on why we have what we have for a typical residence in the US. It's not optimal, but it made sense at the time and now momentum carries it on. Leperfish is right that it's usually not "difficult" to get 3 phase to a home or garage, but it is goddamn expensive when you're the only special snowflake that needs it (so you're paying for that 120 degree wye transformer they have to hang on the pole just for you).
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Jul 5, 2014 22:26
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In induction motors you get more torque out of an equivalent motor, the motor is also more durable. I've also heard they consume less power as they are more efficient. And with an induction stove that we're putting in our new house, it'll definitely benefit from 3-phase, it'll boil a full kettle of water faster than dedicated electric kettle can. I've also wondered they those things weren't more popular in the US. Also finland is pretty big and not densely populated, we're a lot like a US state in that regard. Edit: I think this goes a ways to explaining why 3-phase is more common here: http://electrical-engineering-portal.com/north-american-versus-european-distribution-systems His Divine Shadow fucked around with this message at 22:41 on Jul 5, 2014 |
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Jul 5, 2014 22:32
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Why is it that AC power is referred to as both 110/120 and 220/240? Is it an RMS vs peak difference?
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Jul 6, 2014 01:01
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SkunkDuster posted:Why is it that AC power is referred to as both 110/120 and 220/240? Is it an RMS vs peak difference? It's a variance in what you're going to get at your house. You'll find it anywhere from under 110 to 135+ depending on where you are. Rural areas usually have a lot more variance (due to distance between transformers). While you should bitch to your local utility if this is the case, it may not get you anywhere. In fact, 130V lightbulbs are a thing exactly because of this.
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Jul 6, 2014 01:22
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Until NEMA finally adopts a plug standard that isn't dangerous as gently caress by design, I'm pretty OK without having 240V be the in-home voltage of choice. I like designing at work around 3 phase 208 wye or delta just as much as the next capital equipment automation rear end in a top hat, but I refuse to use NEMA on principle. Begin electrical connector chat.
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Jul 6, 2014 05:25
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Tim Thomas posted:Begin electrical connector chat. You don't like plugs that do this?  What? Are you some kind of person who hates electrical burns and house fires?
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Jul 6, 2014 06:45
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Motronic posted:It's a variance in what you're going to get at your house. I always figured the 130V bulbs were just another way of saying "contractor pack, long life". The house I'm in now had several of the original 130V bulbs... from 1994. They were still working when I started swapping them out for CFLs about 5 years ago. Still have them in a box just in case a CFL craps out and I don't have another handy, plus we have a couple of fixtures that just don't look right with a CFL or LED.Both my UPS and Kill-A-Watt seem to agree that my household voltage ranges from 122-125, depending on the time of day. Sitting at 122 now; I assume because some generation capacity was idled due to it being late at night. It tends to creep up a little during the day, though in the hottest months it'll dip down to about 118 (about the same time ERCOT starts asking people to voluntarily shed loads).
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Jul 6, 2014 06:52
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Tim Thomas posted:Until NEMA finally adopts a plug standard that isn't dangerous as gently caress by design, I'm pretty OK without having 240V be the in-home voltage of choice. I like designing at work around 3 phase 208 wye or delta just as much as the next capital equipment automation rear end in a top hat, but I refuse to use NEMA on principle. I've no complaints about this style:   Also found in a flat non grounded version: 
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Jul 6, 2014 07:13
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Plugchat always makes me so glad of UK mains plugs. Super-safe, you guys. Unless you're treading on one.
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Jul 6, 2014 09:31
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