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True. Ac is a good way to get things to turn, at fixed speeds.
Power supply in the United States versus Europe
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In a manner of speaking, sort of. Edison claimed that 100ish volt DC was a better system than 100is volt AC, and he was dead wrong. The fundamental point is that high voltage distribution is unequivocally superior, and AC allowed for easy up- and down-conversion, which DC did not.
By over a century of then unimaginable progress.
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That's another difference between the US an Europe. The split phase system doesn't exist here. Everything is supplied with 3 phases (230V/400V). Electric stoves and other hard-wired heaters are the typical application for that in residential settings. Power outlets are usually single phase, but one might encounter 3 phase outlets in the garage or in a home workshop.
The human body is not a linear resistor though. I remember volunteering in school for a little demonstration, that involved a hand cranked magneto, two multi-meters for measuring voltage and current and a classmate writing down the measured values at different speeds, while I was holding the leads.
This was also a lesson in (in)effective communication. I wanted my classmates to quickly ramp up to the maximum voltage I was willing to handle instead of slowly turning up the increasingly uncomfortable experiment, so I just told them: "Faster! Faster!". To them, though, I just sounded like a masochist.
At least here rating means "can be used at that voltage" (actually it can be exceeded by 10% on a permanent basis, probably to account for local variations in voltage).
Two common solid wire types here are H05V-U and H07V-U. They are rated 300V/500V and 450V/750V respectively (1 phase/3 phase). Those types are tested at 2000V or 2500V in the latter case.
Reinhard
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user 30299
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That's another difference between the US an Europe. The split phase system doesn't exist here. Everything is supplied with 3 phases (230V/400V). Electric stoves and other hard-wired heaters are the typical application for that in residential settings. Power outlets are usually single phase, but one might encounter 3 phase outlets in the garage or in a home workshop.
The human body is not a linear resistor though. I remember volunteering in school for a little demonstration, that involved a hand cranked magneto, two multi-meters for measuring voltage and current and a classmate writing down the measured values at different speeds, while I was holding the leads.
This was also a lesson in (in)effective communication. I wanted my classmates to quickly ramp up to the maximum voltage I was willing to handle instead of slowly turning up the increasingly uncomfortable experiment, so I just told them: "Faster! Faster!". To them, though, I just sounded like a masochist.
At least here rating means "can be used at that voltage" (actually it can be exceeded by 10% on a permanent basis, probably to account for local variations in voltage).
Two common solid wire types here are H05V-U and H07V-U. They are rated 300V/500V and 450V/750V respectively (1 phase/3 phase). Those types are tested at 2000V or 2500V in the latter case.
Reinhard
Reinhard, I see you are in Austria. I occasionally work in southern Austria, and also central Germany. Many of the homes and Inns that I stay in will use relays with the wall switches for lights and outlets in the room. You flip the switch and you can hear the relay click in the panel box out in the hallway. Is that a common practice ?
Here (at least in some places) you can get three phase into your home, though you may have to argue with the utility to remind them that they are obligated to provide in on request. I had a cousin who wired his house that way.
For heaters, I take it they are run phase-to-phase? Or is something else done to balance the loads, such as running three elements side by side, i.e. "in parallel" physically but not electrically?
Indeed, I oversimplified. Still a "higher amperage system" does not mean that the human body will conduct more more current at 120 V than it would at 240 V.
It's not completely different here. 600 V wire is supposed to withstand 600 V continuously (and is tested higher), but you shouldn't run it that way. Also, the manufacturer's rating isn't the same as what code allows. As I understand it, The National Electric Code (NEC) takes the factors I named into account, and gives the actual allowed values in use. All that has more to do with current carrying capacity, but is somewhat applicable to voltage as well. It pretty much doesn't come up in home wiring.
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I think they are obligated but you may have to pay for the 2 extra transformers and other work the utility may have to do to bring the power to it and your new meter.
Not only that, but many feeders are single phase. Bringing three phase power to a location that’s on a single phase feeder would require replacement of poles (three phase construction is different than single phase) and additional conductors from the last point where 3 phase power was available. The expenses can add up very quickly. Also, the utility must try and balance the load on all three phases. It’s very seldom that three phases are actually needed, and in those instances where a residential customer wants it it’s usually much less expensive to simply buy a phase converter.
heada
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Exactly. When I asked about getting 3-phase service to my house to support some bigger woodworking tools, they required that I set up a business account with them and pay for the transformer and new cable runs. Minimum $25k cost but possibly higher. Ended up being much cheaper to get a phase converter.
Makes sense. When my cousin (once removed) it, it was probably 50 or 60 years ago. Many things have changed since then, like deregulation and the creation of practical solid state phase converters.
A person living on a farm or ranch has an excellent chance to get 3-ph power because a lot of large well pumps for irrigation require it. A person in the suburbs has a lesser chance, but it can be done. I live a quarter mile from a substation. I might actually be able to afford 3-ph if I really needed it.
Every circumstance is different.
heada
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I can throw a rock and almost hit the high tension, high voltage tower from my house but when asked about 100A 3-phase service it was going to be a new line run from the substation 5 miles to the north of me because everything between me and the substation is residential.A person living on a farm or ranch has an excellent chance to get 3-ph power because a lot of large well pumps for irrigation require it. A person in the suburbs has a lesser chance, but it can be done. I live a quarter mile from a substation. I might actually be able to afford 3-ph if I really needed it.
Every circumstance is different.
Exactly - that 34.5 or 69 or 100 kV transmission line running past your house isn’t useful to you at all. You have to get onto a 3-ph distribution line.
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I had a printing business once and the building our office was in already had 3-phase power but my electrician said the copper costs alone were more than just installing a Ronk. This was in the 90's. It was basically a 3-phase motor that somehow was able to be turned with the split phase (don't ask me how) and the 3rd phase was taken off the unused motor winding. Voila 3-phase power for about $200....
rharshberger
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aka a Rotary Phase Converter....a two phase motor turning a 3 phase motor (turns it into a 3 phase generator)...sort of....its what was done before Solid State Phase Converters became affordable.
heada
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Sure wish I could tap off those lines. I'm 2 hours into an estimated 6 hour power outage. Transformer at the substation gave a really nice light show. My UPSes have all run down and gracefullyshut their computers off. Only good news is that it's only 68 outside right now.
Edit: they just added 5 hours to the estimated restore time. Linemen have the worst jobs but we all need them.
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That assumes that irrigation is common where you live. I can't think of a farm I've seen with irrigation equipment anywhere for hundreds of miles.
The prefect in our now defunct Tripoli prefecture bought a used industrial lathe with a 16 inch chuck. It was 3 phase and he told me he acquired a single to 3 phase "converter" to run it in his shop. Don't know anything about it but I don't think he had to use the power company to install it but am unsure. (He's deceased now so I can't ask.)
I never could understand single vs. 3 phase and my paternal grandfather tried to explain it to me. He worked for Northern Illinois Gas Company for 48 years and retired in 1969 at 65. Why would he know about electricity? Back then if there was a big storm that took out electric power and telephones, EVERYONE was called out. Power company, phone company, gas company and any other city utilities guys (tree trimmers) . Grandpa said if a gas line wasn't involved, they took direction from Com-Ed and the phone company guys to help out where they could to restore phone and telephone service. Probably learned a lot from them. Doubt that happens anymore now. Grandpa was an expert plumber too. Heck if one can deal with high pressure gas lines, water lines would be no big deal. Did straight forward wiring too, no doubt from experience gained from working with the power and telephone company guys back in the day during emergencies.
As an aside the Prefect of our local group, acquired a pile of adapters so he could turn smaller casings in the usual HPR range on his "monster" 3 phase lathe. I think he turned a very large P motor but all three flights failed for various reasons. First one over pressurized and blew. Second with a newly turned motor casing flew fine but there was a chute problem (I wasn't there so I didn't witness it) and the rocket hit hard. We later surmised the R/F from the GPS trackers dorked the deployment altimeters. Later did a ground test with the same "new" hardware and discovered that was true. If only the test had occurred pre flight and the disaster could have been avoided. I have the same altimeters and won't fly them with trackers. They work fine otherwise.
Could not repair and salvaged some parts for a new rocket with the motor surviving. Third flight, the motor had a closure failure, blew out from the aft closure dropping burning grains on the ground. Rocket made it off the radio tower rail in slo-mo, tipped over, caught fire and burned after it hit the burning grains on the ground. He gave up on the really large motors after that. I've flown several casings made by him. He bought a second smaller lathe to turn nozzles as the graphite powder gets everywhere even with a vacuum cleaner connected up to get most of the dust while turning. Sorry for rambling but the "3 phase thing" brought back some memories. Kurt
This is more common in larger or connecting rooms like hallways or stairways, where multiple switches control a group of lights. You typically wouldn't see that in, for example, your living room here. If multiple switches are used, the traveler system is the common approach for homes (to the extend that I have seen it).
In theory, it could also be an Instabus based installation. But those are exotic for cost reasons.
Reinhard
That's a big chuck and must have been a decent lathe. A converter and the single phase feeding it would really struggle to cope for the heavy jobs the machine was capable of, but for al-alloy work with modest cuts it sounds like it coped. I can imagine the initial spin-up of a 16" chuck would've probably dimmed a few lights for a moment
TP
My father did this with the family home he had built in the early '50's. Low voltage, low current goes through all the electrical switches in the house and when one flips a switch, a click is heard from the relay downstairs for the selected circuit. Also put a rotary switch in the kitchen so one can turn on any light, anywhere in the house, inside or out. I thought that was really smart given the times back in the day. Kurt
He said it came off of a U.S. Navy ship and had a data plate that read, "Paint approved via "such and such" statute February 1942." It was painted Navy grey but we saw on the supports there were some remnants of Army olive drab so it might have served in the Army too! He got it from a machine shop up in Chicago that I believe was going to all CNC stuff.That's a big chuck and must have been a decent lathe. A converter and the single phase feeding it would really struggle to cope for the heavy jobs the machine was capable of, but for al-alloy work with modest cuts it sounds like it coped. I can imagine the initial spin-up of a 16" chuck would've probably dimmed a few lights for a moment
TP
The prefect used it to turn motor casings and used adapters to turn the smaller ones. Probably didn't take that much power to do.
I was told that 3 phase power was/is common on Navy ships. I sort have wondered what happened to it after the prefect passed away. Might still be sitting in his shop as it would be a "witch" to move. He had a concrete pad poured and had a crane lower the lathe on the pad. Then built the shop walls and roof around it. Now that was hardcore rocketry if you ask me. Kurt
That is pretty damn hard core. I thought I was pretty hard core having a few tonne of 3 phase CNC equipment in the man cave, but I never had to build around it.
TP
TP
boatgeek
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On commercial ships at least, small motors (~1 HP or less) are 120VAC, larger motors (~5 HP or more) are 480VAC, and there's a gray area in the middle where they might be 1 phase 240VAC*, 3 phase 208VAC, or 3 phase 480VAC. That gets a little weird sometimes if there's a large motor on a small boat** that only generates 120 or 240VAC. I believe the Navy boats are similar.
When you get into multiple MW, it's often worth it to go to 690VAC (the top of low voltage in the marine world) to reduce current and required wire size. If you're going really large (like say a cruise ship), it may be worth going to medium voltage somewhere in limited areas. That adds significant new requirements for wire insulation, so you'd need a good reason to go that far.
We have now exhausted my knowledge of
* Technically 2 phases of 120VAC that add up to 1 phase of 240VAC.
** Say with a generating plant smaller than 50 kW--most anything bigger will be 3-phase
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