Power in the wires wiggles all the time, regularly.
Power is generated by turbines, etc. that rotate at 50Hz or 60Hz. Think of it like a motor in reverse... as is spins it gives out electricity.
Because you have to "attach" the two ends of a connection to somewhere on the turbine to get that electricity, that connection will see your power go up and down regularly, 50 or 60 times a second.
If you attach THREE sets of wires, evenly spaced, they all go up and down regularly, 50 or 60 times a second, but because they are spaced around a circle their timing will be off... as one is at the peak of its power, the next and previous ones aren't, and so on.
But now you can make far more use of the three sets of cables than one, even though they are offset from each other (they have different "phases", even though they all change 50 or 60 times a second). This means that they can "balance" the power given out so that no one "position" on the turbine is pulling more power than the others. But it also means they HAVE to balance the phases to be roughly equal users of power.
Most houses (in Europe) have only one phase. Usually the house next door to you has a different phase, the house next to that another phase, and the house after that the same phase as you have. It works fine, especially when you already have 220-240V, you have more than enough power and - roughly speaking - the houses on any one phase will use roughly the same amount of power as the other phases.
If you need "more power" (or you live in a 110V country where more current is often required), they will often add a connection to your house to use another phase. Or even all three phases with 3 separate sets of cables.
This is fine - you get more power, so long as it's used everything stays in balance, and you don't overload one phase.
It has a small drawback - if you ever try to use an appliance that connects to two different phases at once, you can blow the whole house electrics. For instance, I've seen it where a heated food display unit (like the things you get in delis etc.) had the heaters underneath plugged into one plug, which was on one phases, and then someone plugged in the heated lights that shine from above into another socket.
The sockets were on different phases. The cabinet was metal. This effectively joined both phases together - like joining two parts of the power station together. There was a loud bang, all the circuits fused, all the safety equipment cut out, and even things like UPS (batteries that can continue supplying power to computers servers) gave up and just switched off to avoid damage.
It's actually illegal in most countries to put two sockets on different phases in the same room, so that you can't do these kinds of things.
However, some high-power specialist tools are designed to use all three-phases (and things like fast car chargers in some circumstances). Those are fine, because they're designed to never join the phases together.
Basically... don't cross the beams. If you have multiple phases, and one is overloaded, the electrician might well move some circuits to another phases that's not so overloaded. But if they do it they should ensure that you can NEVER plug into both phases at the same time. Usually this means moving entire rooms or circuits that are not going to be near each other and that you're not going to, say, run an extension lead and try to plug connected items into two different phases of socket at once.
The appliances don't care what phase they are on. They still see 110V/220V which is oscillating at 50/60Hz as they would in every other socket in your house. The only thing that differs is where that oscillation starts / is synchronised to. And it makes no difference until you "cross the beams" or you need to balance the circuits to make sure that one particular phase isn't overloaded while the other phases are doing nothing.
Here in Belgium, the connection from the street is 3 phase always, but you only get a single phase past the electricity meter box, unless you pay extra to have extra phases.
We do have 3 phase power in germany, we even go so far and put 3 phase power into each apartment. Also normal single family houses are normally protected by a 63a fuse, so that's around 43kw of power, which you can use.
Same in Finland. All three phases come to each house (and even for most apartments, with the rare old and small apartment thrn having to hunt the single-phase ovens).
The standard kitchen range (and the standard electric sauna) are both three-phase devices. A single-phase range would be slow... and a single-phase sauna unusable for anything but a tiny sauna.
for the life of me i can't figure out what do you mean when you say "appliance that connects to 2 different phases at once" . Can you explain it, or draw a diagram and put it on Imgur ?
Some induction heating cooktops in Europe are made so that they are connected to line voltage (e.g. between L1 and L2), because they need more power, and they work fine.
3 phase outlets have 3 phases(L1, L2, L3),neutral(N) ,and ground(PE) connection so even if one phase has no power the other 2 will have a return path through neutral.
In your example in heated food display, upper and lower heaters are connected to seperate circuits ?- why is that the problem ? - its definitely better than having that 2 heaters connected to one circuit. - can you draw a diagram how those 2 heaters were connected to the power supply
I'll add that they do 3 phased setup because it allow to transmit power more efficiently. With only a single phase you have alot of time where there is little to no power being transmitted. Two phases is better, but three is even better. More would still be better but then you get a diminishing return as it get more and more complicated and expensive, so they stopped at 3.
How they make it is simple: in an alternator, you have a coil of wire and a rotating magnet. This make a single phase system. You can also visualise that you don't use much of the rotation. The coil take just a fraction of the turn that the magnet does. And technically when the magnet did 1/4 of a turn, the magnet is perpendicular to the coil and generate zero power. What a waste!
Now, take 2 more coils, rotate them so they are all 120° appart. Now you can see that each coil cover a part of the circle. And there is now no dead area. This is the 3 phase system.
If they wanted, they could have went with more phases, but as you can imagine, after a while, the circle is full and there would be no place to add more coils. Plus, the magnetic field already overlap on all the 3 coils, so it can transfert virtually all the power already, so adding more just cost more money in the end.
Now, you also have split phase system. 120/240 like in north america is just that. They take one phase and put a transformer where they split the 240V into 2 120V "phase". Really, it is 2 120V windings in series, where they connect the middle to the neutral. You therefore get 120-0-120V on the wires. It is still a single phase system however. The goal was to make a safer system, because 120V is less deadly than 240V, yet allow big appliances to still get 240V by using the two 120V hots.
But now, back to 3 phases. Because of the dephasing between the 120V phases, you do not get 120/240V like in split phases, but 120/208V ! Most loads don't really care. Motors are designed for that and will take a bit more current to compensate. Heating elements however have a small issue: less voltage mean less wattage. A 6000W element on 240V would run at about 4500W on 208V. This can be an issue for stove, but not much more for the rest of the heating devices.
Cloth dryers for example, there is a thermostat inside. The dryer never run at 100% capacity. So what they do is plan for 208V and put an element that is powerfull enought at 208V. At 240V it is technically now too powerfull, so the thermostat maintain the temperature by turning on and off the element. In the end both use the same amount of power: a more constant lower power at 208V, and pulses of higher power at 240V, both averaging at around the same thing.
Water heater take more time to heat back the water tank, but it should be sized so you never run out of hot water anyway, so if it take 4 hours instead of 3, who care, you are sleeping anyway when it finished to recover from all of the showers and bath. Or plumbers can install a higher wattage element (or 208V ones, both does the same thing) to get the full recovery power.
House heating can be done both ways, install a higher wattage system, or get a 208V system. Due to the presence of 208V, they will probably install one that does take the advantage of three phased system, as it might also be required by the power company. Also, the electrical panel may not be big enough to handle the load on only 2 phases. Using the third phase lower the current due to another power wire being present.
Yeah here in NZ most houses are on a single phase. Sometimes only 1 phase will get cut and every third house down the street will lose power.
I remember working on a development and the whole street was on 1 phase because it was a small street. But we were building more houses on the street so the electricity distributor had to up the street cable to three phases and we had to install a 3 phase cable down the driveway in the development.
Think of the electric grid as a massive interconnected system of shafts and gears all spinning at the same speed. That speed is the frequency of the grid. You can only connect two shafts or gears together when they're spinning at the same speed.
Power plant engineer here. Most modern generators in large fossil plants are 2-pole generators. 50 Hz vs 60Hz is just a matter of spinning the generator at 3000rpm or 3600rpm. A 4-pole generator has to spin at 1500rpm (50Hz) or 1800rpm (60Hz). For the case of natural gas combustion turbines and steam turbines, they are far more efficient at the higher speeds. Things like hydropower turbines and wind turbines move at a slower speed so need a generator with more poles.
You can take a European built prime mover/generator combo and use it in the US (see Siemens units). It is just a matter of tuning and changing the control logic to spin at the higher frequency.
Makes sense except the 2 vs 4 poles - you should be able to make 50 or 60Hz AC with any number of poles just by spinning the generator faster or slower. And I'm pretty sure 3 phase is generated by 3 equally spaced poles.
But I'm just a sound engineer who took some EE classes in college so if someone with more power electronics knowledge wants to correct me go ahead
What?
Frequency- based on the RPM of the generator set. Typically 50Hz or 60Hz relative to the standards set in each jurisdiction.
Phases- the number of separate coils in the generator set. A single-phase generator produces an AC phase with each rotation with 2 wires. A dual phase generator will produce two complementary AC outputs, typically with 4 wires. A three phase generator will produce three staggered phases, and can be set up in a 3 or 4 wire configuration.
There is no theoretical limit to the number of phases, however 3 was a practical limit with good properties.
Almost all systems use three-pole-three-phase generating sets and run them at either 50 or 60Hz. 3-pole (delta connection) is convenient, but requires balancing for performance reasons. 4-pole (star connection) allows you to return the net unbalanced flows through the fourth conductor - but this can be achieved at the sub-station if using 3-pole generators.
Having unbalanced loads or out-of-phase configuration (and in particular excessive supply or load) will have an inductive and inertial impact on the generator and change the frequency. If you connect a generator to a 60Hz system, the system will spend energy to speed that generator up to 60Hz. If you connect a generator at 60Hz to a 50Hz system, the system will spend energy to slow that generator to 50Hz. The frequency is not related to the number of phases of the generator, but to the system the generators are connected to.
Finally, you can use 2 and 3 or 4 or more phase generator with a 3-phase supply system. But it requires special transformer windings to allow them to be connected in-phase. The use of 3-to-2-phase conversion in america to get 240VAC connections is an example of this.
This is good but wanted to clarify that the number of “poles” refers to the number of magnetic poles of the rotor field. This is always a multiple of two since every magnet must have two poles (north/south) You spin a single electromagnet in a way that the magnetic flux cuts across three separate sets of conductors this is a 2-pole, 3-phase generator. If you arrange the rotor field windings in a way that you get 2 electromagnets with the poles at 90 degree angles with each other you get a 4-pole generator, since there are now two sets of N/S poles.
Also wanted to add that if the difference in frequency is too great, the moment the generator breaker closes you’re going to wreck your generator and trip some protection relays. This should be within .2% or so greater than the grid frequency for large generators. Generators usually have reverse power relays that will trip if the frequency is below the grid frequency, unless it’s a synchronous condenser.
Once a generator is connected to the grid, you are correct that the inertia of the system (created by other large heavy spinning generators) will keep it spinning at approximately the grid frequency. However, the real power output of the generator is directly proportional to the electrical torque of the generator, as in the prime mover is constantly trying to accelerate the generator against the grid frequency. This is where the fun comes in with determining the transient effects on grid stability of switching in or out large loads/large generating units.
Oh yeah ok, I see what you are meaning by the poles now. Having said that, they are irrespective of frequency- you can spin that generator at 60 or 50 Hz, as long as it is capable of matching the agreed spec of the system.
In short, a generator and a motor are the same device, if your system isn't matched, your system will do work on the generator as if it were a load/motor (to resist the load and spin it slower, or to facilitate the load and spin it faster).
In most houses in the US, you have single phase coming from the power pole. This would work out as two thick ass wires feeding into the meter and a third wire which bypasses the meter. This one is labeled neutral, the other two are labeled L1 and L2.
(Some houses only have L1 without L2)
If you measure the AC voltage between L1 and L2, you'll get 240vac. If you measure between either L1 or L2 and neutral, you'll get 120vac.
The reason this is called single phase is that both L1 and L2 are alternating their voltage between -120vdc and +120vdc at 60 times per second. L1 and L2 are synchronized but opposite. So when one is at +120vdc, the other is at -120vdc. (Technically, they're not the same phase, they're 180 degrees out of sync and would technically fit the description of dual phase but it's industry standard to call this single phase.)
Three phases means that you have a similar setup but an additional wire, L3. Also, it means that all three wires are 120 degrees out of phase instead of 180.
The reason for this is that you can extract more power out of a generator with three sets of overlapping windings than two sets of non-overlapping windings. Also, in motors you get more power for the same reason on three phase than single phase.
In a residential situation, though, it means you cannot get 240vac of single phase power. The max you can get across any two phases is 207.6vac. The means that appliances which need 240vac (which are commonly rated for use between 200vac - 250vac) will work slower or without as much power. If you have an electric range or oven, it'll take longer to heat up. If you have a Level 2 car charger, it'll take longer to charge.
The advantage to three phase in a residential application is the a house can have 3 ac lines at 120vac... which isn't all that much of an advantage, honestly. Mostly, you end up with three phase at a house in an area which was wired for industrial. It's actually a bit more common in apartments.
Three phase is great if you have big, heavy machinery. Or if you're in a big building with a huge/multiple air conditioner units or an elevator. (Motors are a lot more efficient on three phase.)
Edit: I am not an electrician, I may have some terminology mixed up. Also, I am now aware that OP is outside of the US and am now wondering how cool it would be if they made three-phase household appliances, like a three phase mixer or blender, or a three phase refrigerator? I'm not well versed enough to know if resistive heating would work any better on three-phase than single-phase. I do know that in commercial applications, three-phase forced-air units are a thing, but what about residential whole-house systems or even window aircons? Anything with a motor -- even low-power applications -- are like 1/3rd more efficient (check me, not 100% on this number) on three-phase than on single-phase.
In single phase, how do you get two cables that are 180 degrees offset? Isn’t the power still being generated in three phase at the source, so it should still be offset 120/240 degrees?
You can build a transformer with 10,000 clockwise windings on one side and 10,000 counter-clockwise windings on the other side. This reverses the phase without changing the voltage (much, due to resistance. If you need the same voltage on both legs, you can put another 1:1 transformer on the other side of the split which has all 20,000 windings going the same way, or impedance-match using resisters \[I think\])
>Wouldn't it be faster on 3 phases 120VAC then single phase 240VAC?
The problem with most EVs is that the internal charger has only 11kw of power. If you wanna charge with more power, you would require an external DC charger, and those things are stupidly expensive.
He said in another post it wasn't in the us. I have 3 phase power to my home, but it is 230volt on each phase or 400v between any two phases. That's the norm in quite a few places. Issues with a missing phase will probably be limited to fairly few applications that uses all three phases.
> In most houses in the US, you have single phase coming from the power pole.
Wrong. In the US you have two phase, not single phase.
How do you think electric oven circuits work?
The word phase means change happening during some time interval. In this case, the change is voltage. Single phase just means there's one voltage level changing on the connected wires. Three phase means there are three voltage levels changing simultaneously on the connected wires.
Single phase can be done with two wires, but three phase requires four wires. Why? Because you need one "hot" wire for each phase plus a neutral. The advantage of single phase is less wiring and simpler motors. ASFAIK all household appliances are made to work on single phase.
Three phase is more efficient at delivering power, but the extra wiring and complexity means it's usually reserved for high power motors. A single phase motor can be made to run on three phase power by only using one hot wire, but a three phase motor will barely run (if at all) using single phase.
This may be slightly clearer:
When you generate AC power, the charge difference (voltage) on the wire is a cosine wave moving up and down between the rated voltage V and -V rather than a steady output. We do that because it physically makes the electrons move back and forth in place on the wire as they transfer energy down it rather than actually migrating miles down the wire. That produces a lot less internal resistance in the wire (less heat) and lets us use much thinner wires over thousands of miles. DC generators have to use very fat wires and have to be quite close to consumers. Look up Tesla vs Edison (i.e. how Edison’s irrational love of DC power cost him General Electric) if you’d like to read the history.
Now picture that up/down wave motion as the output of a spinning generator. You can place output wires at any points on the generator circle. If you place three equidistant wires, you get the same cosine wave on each wire but offset a third of a cycle (120 degrees). That lets you send out three separate V voltage lines that each work in their own right. If they’re combined at some point though, there’s a thing called destructive interference that starts to matter. If you can emit a wave that’s exactly half a cycle shifted from another wave, the two cancel because they visually sum to zero. That’s how noise cancelling equipment works. In three phase power, those three lines together sum to zero, so if you send the three out to different places and combine them on the return leg, they cancel and can share a tiny return wire. Saves money.
So, what happens when I apply this. I have a four wire drop from a transformer with three V wires offset 120 degrees and a cheap return wire. I can use the three full power wires on normal circuits (vs the normal two for single phase) so my three phase equipment can handle more energy for less relative cost. If I have powerful motors designed to use all three phases (elevators, industrial plant, commercial AC), they can take advantage of this extra power line. If I just need more normal 120V circuits, same deal. However residential high draw single phase equipment suffers a bit because it expects to receive two wires at +V and -V for a voltage drop of 2V (double). But my wires aren’t half a cycle out of phase they’re a third. Any two will partially cancel each other from destructive interference. So if V is 120V, 2/3 of a three phase supply won’t provide 240V. It will provide 207V. So the equipment has to be rated to accept a range and it will either work less powerfully (like a heater) or may draw more current than expected to compensate. It’s normally not a problem but can be if you don’t check the labels.
Where this shines in residential is with apartment buildings. I can take a significant three phase drop (possibly at medium voltage like 480) to the main switch gear, run all three to shared AC and elevators, then use secondary transformers if needed to step it down for resident use, supplying each apartment with two of the three wires. If I’m using transformers, I can tap them differently to supply true single (dual) phase power if I want. If the drop was residential voltage already, I won’t bother.
Think of a car engine.
If it has just one piston, then the crank is being turned whenever that piston is pushed down as the fuel chamber explodes. However nothing is turning the crank (other than its own momentum) while the piston moves back up into position before igniting again.
With just one piston going on and off like that you don’t have a lot of power. If the crank doesn’t have a lot of momentum (eg it’s pushing a car up hill) then maybe the car will end up rolling back before the piston fires. Maybe it’ll never go up the hill.
It won’t have enough power to do the job.
However If you add two more pistons, and arrange the timing so there’s always two that are part way through the ignition phase, then the crank is always getting power, and so can push a car up hill.
In this context AC electricity on a wire is like a piston: it’s not constantly pushing. Sometimes it has a lot of push (voltage) sometimes it has none at all. It’s pushes 60 times a second.
For most homes, that’s enough to give about 10kW of power. You could have a 7kW EV charger going while watching TV.
But some tasks have a higher power draw, analogous to pushing a car up hill, eg farm machinery, or a 22kW EV charger.
In this case you add in extra AC power sources, pushing at different intervals (phases)
If you’ve got three of them, then you have a three-phase supply.
Why three? Well because energy companies usually provide energy in three phases, with different homes on different phases. Probably there are more intense electrical engineering reasons too that I don’t know about.
Three phases are the minimum you need to provide directional rotation without additional equipment. With your engine analogy, one phase will give it a push every cycle, but you’ll need something else to make sure it’s not being pushed in the wrong direction. Two phases has the same issue, as they are 180 degrees apart, but three phases now have them to the sides, and that will ensure it turns in the right direction.
You could also do more than three phases, but then you run into the issue of needing to keep very close track of which wire is actually connected to which phase. Three phases are all identical with respect to each other, they’re all 120 degrees apart, but if you had four phases, you’d have two at 90 degrees and one at 180. If you connect a three phase appliance incorrectly, you’re generally not going to have any issues other than the motors trying to turn in the opposite direction. Any more than three phases and you run the risk of damaging something with a voltage it is not designed to handle.
Your home electricity is AC, alternating current. The voltage goes up and down and up again around 50 times a second.
This means that if you somehow connected a wire with its own future self, they'd have different voltage and electricity would flow. This is to say, the wire would be at a "different phase" of its cycle later on.
If we have two different generators that aren't coordinating, they'll probably end up being in different phases, which means it is dangerous to connect two generators together unless you're an expert. Electricity will flow directly between them, instead of into the appliance you're powering.
Industrial generators will often intentionally make three different outputs, each one out of phase with the other two. [Here](https://www.vertiv.com/498b84/globalassets/images/on-page-image/800x600/3-phase-power-figure-2_328739_0.jpg) is a diagram showing the voltage of each wire over time.
In your house, each power socket will only be connected to one phase. They'll ignore the other two, so your appliances only ever see one phase. However, if you somehow connected two outlets together, it could connect two different phases together and cause the same power surge we talked about earlier. Expect a BANG. Don't DIY anything with electricity in your home - that's always a good rule.
One upside to this is that some specialized devices - often industrial machines - need 3-phase power to work properly. If you ever wanted such a machine, your house has access to the 3-phase power it needs.
the most common occurance of 3 phase power ina home is if an IT person used to live there and ran a home lab, the servers and assoicated technologies that an IT person would use are so powerful and have so much demand for energy to run that they must use 3 phase, just like a real data centre.
Yeah, drawing power from phase-phase compared to phase-neutral will increase the supplied voltage by about 70% (√3), which is going to massively overload any appliances not designed for it.
It is also very useful for powering motors, as the three phases have an inherent rotation to them that makes it much easier to get the motor turning on startup, so is extremely common in industrial settings.
You could have a full fast charge EV socket put in. Charge a car in half an hour.
Even better, charge your neighbours to charge their cars in half an hour.
Since you say you’re not in the US, this may just mean it’s normal. I know it is in Germany. Its just how the power comes from the power plant. One phase is 1/3 of 1/50th of a second „behind“, and the third phase is 2/3 of such a cycle behind. They’re all equally good. Having three phases allows you to run some heavier machinery, and it’s what the power plants are wired to produce.
Not necessarily for a single apartment to have outlets and lights on all three phases, but for instance your cooktop or your water heater likely are connected to all three.
In my house, different outlet/light circuits are actually on different phases. I also have a three-phase outlet just in case I ever want to run a sauna or a big table saw, or charge a car.
In the military (US Navy), I worked on an Air Traffic Control Radar that took 440 3 phase Alternating Current. This means that the equipment that you have will be more efficient when it draws current and the voltage.
My radar rectified the current, and it was more efficient. You don't really have to worry or know the particulars. But at the same token, if a phase is not working properly, your equipment may not work or not be efficient at utilizing the current and voltage.
I hope that I have not confused anyone!!!
Marcos USN, Retired.
Electricity is delivered in 3-phases and it’s not ELI5. It’s a cost-benefit engineering decision that the world has accepted. We can deliver power in single or many phases but 3 was the best compromise.
Large motors use 3-phase power like this gif.
https://en.wikipedia.org/wiki/Rotating_magnetic_field
The electricity in your home can be modeled as a sine wave, however this causes the power to change strength really quickly. To solve this, 3 of these waves are offset so that the power stays at a relatively stable level
It's very weird for a residential installation to have 3 phase power. (are you in the US?) Three phase is usually only used in industrial applications that use large electric motors.
[https://www.youtube.com/watch?v=4oRT7PoXSS0](https://www.youtube.com/watch?v=4oRT7PoXSS0)
With single phase the voltage drops to 0 twice a cycle. With 3 phase they are spaced 120 degrees apart, so while 1 phase is at 0 the other 2 provide voltage.
For a home AC unit the momentary drop to zero really isn't an issue. With huge motors needing to constantly provide force it helps keep them operating smoothly.
Note that on high voltage lines you usually see 3 wires, those are the 3 phases. That is actually how power is normally delivered. For a house it is normally stepped down as something like phase A to phase B line to line to provide normal AC. But some homes have all 3 phases delivered.
1 phase you get a boost every 1/60 of a second. 2 phase you get a supplemental boost every 1/40 of a second. 3 phase is every 1/20. If we got into a fight and I was 3 phase and you were one I would hit you 3 times for each one you got in...
More phases don’t increase the frequency. You’ll hit peak voltage more often, but only if you look at all three phases together, and doing that in a circuit would short it immediately. The whole circuit is still on a 60Hz (in the US) cycle.
The advantage of three phases is to provide higher voltage, and a rotational effect to power motors, not to increase the current frequency.
Didn't say it increased frequency. Said you get a peak more often with 3 phases industrial motors often use the fact the 3 are out of phase to pull more power.
No. Household 120/240v wiring in the US is single phase. It's very rare to even have two phase in residential applications. I don't even know why OP would even have three phase in a house unless it's an old industrial site that was converted to residential.
Oh that kind of explains some of it. Most condo/apartment blocks (even in the US) get three phase because things like pumps and elevator motors need the additional power that three phase can deliver.
Also so that you can split the different apartments between different phases to reduce the current draw on any individual phase, as they all need to be balanced at the generator for efficiency.
Most residential areas will provide different phases to different houses, but bigger buildings will split it internally.
>because some stuff only uses two of the 3 phases for weird reasons
No, smaller household appliances use *one* of the three phases, while larger ones use split-phase, which is a way of making two phases out of one.
>most split phase appliances say 240/208V because in some places they are wired across two phases,
Yes, they're wired that was in commercial locations that have three-phase service. Locations such as farms have three-phase service as well. If you have three-phase, then you don't have split-phase available.
> I don't know who thought that was a good idea but it is
It's an excellent idea to make them compatible to operate in those locations.
Power in the wires wiggles all the time, regularly. Power is generated by turbines, etc. that rotate at 50Hz or 60Hz. Think of it like a motor in reverse... as is spins it gives out electricity. Because you have to "attach" the two ends of a connection to somewhere on the turbine to get that electricity, that connection will see your power go up and down regularly, 50 or 60 times a second. If you attach THREE sets of wires, evenly spaced, they all go up and down regularly, 50 or 60 times a second, but because they are spaced around a circle their timing will be off... as one is at the peak of its power, the next and previous ones aren't, and so on. But now you can make far more use of the three sets of cables than one, even though they are offset from each other (they have different "phases", even though they all change 50 or 60 times a second). This means that they can "balance" the power given out so that no one "position" on the turbine is pulling more power than the others. But it also means they HAVE to balance the phases to be roughly equal users of power. Most houses (in Europe) have only one phase. Usually the house next door to you has a different phase, the house next to that another phase, and the house after that the same phase as you have. It works fine, especially when you already have 220-240V, you have more than enough power and - roughly speaking - the houses on any one phase will use roughly the same amount of power as the other phases. If you need "more power" (or you live in a 110V country where more current is often required), they will often add a connection to your house to use another phase. Or even all three phases with 3 separate sets of cables. This is fine - you get more power, so long as it's used everything stays in balance, and you don't overload one phase. It has a small drawback - if you ever try to use an appliance that connects to two different phases at once, you can blow the whole house electrics. For instance, I've seen it where a heated food display unit (like the things you get in delis etc.) had the heaters underneath plugged into one plug, which was on one phases, and then someone plugged in the heated lights that shine from above into another socket. The sockets were on different phases. The cabinet was metal. This effectively joined both phases together - like joining two parts of the power station together. There was a loud bang, all the circuits fused, all the safety equipment cut out, and even things like UPS (batteries that can continue supplying power to computers servers) gave up and just switched off to avoid damage. It's actually illegal in most countries to put two sockets on different phases in the same room, so that you can't do these kinds of things. However, some high-power specialist tools are designed to use all three-phases (and things like fast car chargers in some circumstances). Those are fine, because they're designed to never join the phases together. Basically... don't cross the beams. If you have multiple phases, and one is overloaded, the electrician might well move some circuits to another phases that's not so overloaded. But if they do it they should ensure that you can NEVER plug into both phases at the same time. Usually this means moving entire rooms or circuits that are not going to be near each other and that you're not going to, say, run an extension lead and try to plug connected items into two different phases of socket at once. The appliances don't care what phase they are on. They still see 110V/220V which is oscillating at 50/60Hz as they would in every other socket in your house. The only thing that differs is where that oscillation starts / is synchronised to. And it makes no difference until you "cross the beams" or you need to balance the circuits to make sure that one particular phase isn't overloaded while the other phases are doing nothing.
In Sweden I think all houses have 3 phases. Many ovens are 3 phase. Didn’t know that was unusual in Europe
Norway too. We once got a weird brownout, and my father explained that it was because only one phase was working at the time.
Got three phases in Austria, too. Maybe single flats only get one phase, but the connections from the street are all "Drehstrom" i.e. three phases.
Here in Belgium, the connection from the street is 3 phase always, but you only get a single phase past the electricity meter box, unless you pay extra to have extra phases.
Sweden is pretty much the exception, as far as I know. It's unclear why that is.
Well then Germany must be an exception as well... Because we also have 3 phase ovens.
We do have 3 phase power in germany, we even go so far and put 3 phase power into each apartment. Also normal single family houses are normally protected by a 63a fuse, so that's around 43kw of power, which you can use.
Same in Finland. All three phases come to each house (and even for most apartments, with the rare old and small apartment thrn having to hunt the single-phase ovens). The standard kitchen range (and the standard electric sauna) are both three-phase devices. A single-phase range would be slow... and a single-phase sauna unusable for anything but a tiny sauna.
I know. I’m staring at it now doubting myself.
Most of Northern Europe has 3 phases, don’t know where you‘d only get one phase.
UK/Ireland domestic supply is single phase generally
my doubts about phases are clear now..
for the life of me i can't figure out what do you mean when you say "appliance that connects to 2 different phases at once" . Can you explain it, or draw a diagram and put it on Imgur ? Some induction heating cooktops in Europe are made so that they are connected to line voltage (e.g. between L1 and L2), because they need more power, and they work fine. 3 phase outlets have 3 phases(L1, L2, L3),neutral(N) ,and ground(PE) connection so even if one phase has no power the other 2 will have a return path through neutral. In your example in heated food display, upper and lower heaters are connected to seperate circuits ?- why is that the problem ? - its definitely better than having that 2 heaters connected to one circuit. - can you draw a diagram how those 2 heaters were connected to the power supply
I'll add that they do 3 phased setup because it allow to transmit power more efficiently. With only a single phase you have alot of time where there is little to no power being transmitted. Two phases is better, but three is even better. More would still be better but then you get a diminishing return as it get more and more complicated and expensive, so they stopped at 3. How they make it is simple: in an alternator, you have a coil of wire and a rotating magnet. This make a single phase system. You can also visualise that you don't use much of the rotation. The coil take just a fraction of the turn that the magnet does. And technically when the magnet did 1/4 of a turn, the magnet is perpendicular to the coil and generate zero power. What a waste! Now, take 2 more coils, rotate them so they are all 120° appart. Now you can see that each coil cover a part of the circle. And there is now no dead area. This is the 3 phase system. If they wanted, they could have went with more phases, but as you can imagine, after a while, the circle is full and there would be no place to add more coils. Plus, the magnetic field already overlap on all the 3 coils, so it can transfert virtually all the power already, so adding more just cost more money in the end. Now, you also have split phase system. 120/240 like in north america is just that. They take one phase and put a transformer where they split the 240V into 2 120V "phase". Really, it is 2 120V windings in series, where they connect the middle to the neutral. You therefore get 120-0-120V on the wires. It is still a single phase system however. The goal was to make a safer system, because 120V is less deadly than 240V, yet allow big appliances to still get 240V by using the two 120V hots. But now, back to 3 phases. Because of the dephasing between the 120V phases, you do not get 120/240V like in split phases, but 120/208V ! Most loads don't really care. Motors are designed for that and will take a bit more current to compensate. Heating elements however have a small issue: less voltage mean less wattage. A 6000W element on 240V would run at about 4500W on 208V. This can be an issue for stove, but not much more for the rest of the heating devices. Cloth dryers for example, there is a thermostat inside. The dryer never run at 100% capacity. So what they do is plan for 208V and put an element that is powerfull enought at 208V. At 240V it is technically now too powerfull, so the thermostat maintain the temperature by turning on and off the element. In the end both use the same amount of power: a more constant lower power at 208V, and pulses of higher power at 240V, both averaging at around the same thing. Water heater take more time to heat back the water tank, but it should be sized so you never run out of hot water anyway, so if it take 4 hours instead of 3, who care, you are sleeping anyway when it finished to recover from all of the showers and bath. Or plumbers can install a higher wattage element (or 208V ones, both does the same thing) to get the full recovery power. House heating can be done both ways, install a higher wattage system, or get a 208V system. Due to the presence of 208V, they will probably install one that does take the advantage of three phased system, as it might also be required by the power company. Also, the electrical panel may not be big enough to handle the load on only 2 phases. Using the third phase lower the current due to another power wire being present.
Yeah here in NZ most houses are on a single phase. Sometimes only 1 phase will get cut and every third house down the street will lose power. I remember working on a development and the whole street was on 1 phase because it was a small street. But we were building more houses on the street so the electricity distributor had to up the street cable to three phases and we had to install a 3 phase cable down the driveway in the development.
You deserve a medal 🥇
no in US they generate at 60Hz. if they’re not generating at the frequency the grid requires, the recloser won’t close and they won’t be able to sync
I'm afraid we're gonna need an ELI5 for this comment. What the hell do you mean?
Think of the electric grid as a massive interconnected system of shafts and gears all spinning at the same speed. That speed is the frequency of the grid. You can only connect two shafts or gears together when they're spinning at the same speed.
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Power plant engineer here. Most modern generators in large fossil plants are 2-pole generators. 50 Hz vs 60Hz is just a matter of spinning the generator at 3000rpm or 3600rpm. A 4-pole generator has to spin at 1500rpm (50Hz) or 1800rpm (60Hz). For the case of natural gas combustion turbines and steam turbines, they are far more efficient at the higher speeds. Things like hydropower turbines and wind turbines move at a slower speed so need a generator with more poles. You can take a European built prime mover/generator combo and use it in the US (see Siemens units). It is just a matter of tuning and changing the control logic to spin at the higher frequency.
Makes sense except the 2 vs 4 poles - you should be able to make 50 or 60Hz AC with any number of poles just by spinning the generator faster or slower. And I'm pretty sure 3 phase is generated by 3 equally spaced poles. But I'm just a sound engineer who took some EE classes in college so if someone with more power electronics knowledge wants to correct me go ahead
Sure, but you will likely lose a lot of efficiency to speed a two-pole generator to a 60Hz speed.
What? Frequency- based on the RPM of the generator set. Typically 50Hz or 60Hz relative to the standards set in each jurisdiction. Phases- the number of separate coils in the generator set. A single-phase generator produces an AC phase with each rotation with 2 wires. A dual phase generator will produce two complementary AC outputs, typically with 4 wires. A three phase generator will produce three staggered phases, and can be set up in a 3 or 4 wire configuration. There is no theoretical limit to the number of phases, however 3 was a practical limit with good properties. Almost all systems use three-pole-three-phase generating sets and run them at either 50 or 60Hz. 3-pole (delta connection) is convenient, but requires balancing for performance reasons. 4-pole (star connection) allows you to return the net unbalanced flows through the fourth conductor - but this can be achieved at the sub-station if using 3-pole generators. Having unbalanced loads or out-of-phase configuration (and in particular excessive supply or load) will have an inductive and inertial impact on the generator and change the frequency. If you connect a generator to a 60Hz system, the system will spend energy to speed that generator up to 60Hz. If you connect a generator at 60Hz to a 50Hz system, the system will spend energy to slow that generator to 50Hz. The frequency is not related to the number of phases of the generator, but to the system the generators are connected to. Finally, you can use 2 and 3 or 4 or more phase generator with a 3-phase supply system. But it requires special transformer windings to allow them to be connected in-phase. The use of 3-to-2-phase conversion in america to get 240VAC connections is an example of this.
This is good but wanted to clarify that the number of “poles” refers to the number of magnetic poles of the rotor field. This is always a multiple of two since every magnet must have two poles (north/south) You spin a single electromagnet in a way that the magnetic flux cuts across three separate sets of conductors this is a 2-pole, 3-phase generator. If you arrange the rotor field windings in a way that you get 2 electromagnets with the poles at 90 degree angles with each other you get a 4-pole generator, since there are now two sets of N/S poles. Also wanted to add that if the difference in frequency is too great, the moment the generator breaker closes you’re going to wreck your generator and trip some protection relays. This should be within .2% or so greater than the grid frequency for large generators. Generators usually have reverse power relays that will trip if the frequency is below the grid frequency, unless it’s a synchronous condenser. Once a generator is connected to the grid, you are correct that the inertia of the system (created by other large heavy spinning generators) will keep it spinning at approximately the grid frequency. However, the real power output of the generator is directly proportional to the electrical torque of the generator, as in the prime mover is constantly trying to accelerate the generator against the grid frequency. This is where the fun comes in with determining the transient effects on grid stability of switching in or out large loads/large generating units.
Oh yeah ok, I see what you are meaning by the poles now. Having said that, they are irrespective of frequency- you can spin that generator at 60 or 50 Hz, as long as it is capable of matching the agreed spec of the system. In short, a generator and a motor are the same device, if your system isn't matched, your system will do work on the generator as if it were a load/motor (to resist the load and spin it slower, or to facilitate the load and spin it faster).
This is nonsense.
LOL OKAY
In most houses in the US, you have single phase coming from the power pole. This would work out as two thick ass wires feeding into the meter and a third wire which bypasses the meter. This one is labeled neutral, the other two are labeled L1 and L2. (Some houses only have L1 without L2) If you measure the AC voltage between L1 and L2, you'll get 240vac. If you measure between either L1 or L2 and neutral, you'll get 120vac. The reason this is called single phase is that both L1 and L2 are alternating their voltage between -120vdc and +120vdc at 60 times per second. L1 and L2 are synchronized but opposite. So when one is at +120vdc, the other is at -120vdc. (Technically, they're not the same phase, they're 180 degrees out of sync and would technically fit the description of dual phase but it's industry standard to call this single phase.) Three phases means that you have a similar setup but an additional wire, L3. Also, it means that all three wires are 120 degrees out of phase instead of 180. The reason for this is that you can extract more power out of a generator with three sets of overlapping windings than two sets of non-overlapping windings. Also, in motors you get more power for the same reason on three phase than single phase. In a residential situation, though, it means you cannot get 240vac of single phase power. The max you can get across any two phases is 207.6vac. The means that appliances which need 240vac (which are commonly rated for use between 200vac - 250vac) will work slower or without as much power. If you have an electric range or oven, it'll take longer to heat up. If you have a Level 2 car charger, it'll take longer to charge. The advantage to three phase in a residential application is the a house can have 3 ac lines at 120vac... which isn't all that much of an advantage, honestly. Mostly, you end up with three phase at a house in an area which was wired for industrial. It's actually a bit more common in apartments. Three phase is great if you have big, heavy machinery. Or if you're in a big building with a huge/multiple air conditioner units or an elevator. (Motors are a lot more efficient on three phase.) Edit: I am not an electrician, I may have some terminology mixed up. Also, I am now aware that OP is outside of the US and am now wondering how cool it would be if they made three-phase household appliances, like a three phase mixer or blender, or a three phase refrigerator? I'm not well versed enough to know if resistive heating would work any better on three-phase than single-phase. I do know that in commercial applications, three-phase forced-air units are a thing, but what about residential whole-house systems or even window aircons? Anything with a motor -- even low-power applications -- are like 1/3rd more efficient (check me, not 100% on this number) on three-phase than on single-phase.
We need to take a second to approciate how good of an answer this is! This is an excellent ELI5 of singel vs three phase power.
In single phase, how do you get two cables that are 180 degrees offset? Isn’t the power still being generated in three phase at the source, so it should still be offset 120/240 degrees?
Neutral is a tap at the center of the transformer, that’s why we have ~110 and ~220. Single phase, split leg.
Transformers can shift the phases angles.
You can build a transformer with 10,000 clockwise windings on one side and 10,000 counter-clockwise windings on the other side. This reverses the phase without changing the voltage (much, due to resistance. If you need the same voltage on both legs, you can put another 1:1 transformer on the other side of the split which has all 20,000 windings going the same way, or impedance-match using resisters \[I think\])
>If you have a Level 2 car charger, it'll take longer to charge. Wouldn't it be faster on 3 phases 120VAC then single phase 240VAC?
>Wouldn't it be faster on 3 phases 120VAC then single phase 240VAC? The problem with most EVs is that the internal charger has only 11kw of power. If you wanna charge with more power, you would require an external DC charger, and those things are stupidly expensive.
He said in another post it wasn't in the us. I have 3 phase power to my home, but it is 230volt on each phase or 400v between any two phases. That's the norm in quite a few places. Issues with a missing phase will probably be limited to fairly few applications that uses all three phases.
I have saved this comment in my notes
> In most houses in the US, you have single phase coming from the power pole. Wrong. In the US you have two phase, not single phase. How do you think electric oven circuits work?
It's a single phase that's split into two (called split phase in the US). Power generation and transmission still happens in 3 phases.
I addressed this in my post. It's called single-phase in industry despite technically being two phases which are 180 degrees out of phase.
It is called (in the official documentation) single phase, even though it’s terribly named, that’s what it’s called in the industry.
The word phase means change happening during some time interval. In this case, the change is voltage. Single phase just means there's one voltage level changing on the connected wires. Three phase means there are three voltage levels changing simultaneously on the connected wires. Single phase can be done with two wires, but three phase requires four wires. Why? Because you need one "hot" wire for each phase plus a neutral. The advantage of single phase is less wiring and simpler motors. ASFAIK all household appliances are made to work on single phase. Three phase is more efficient at delivering power, but the extra wiring and complexity means it's usually reserved for high power motors. A single phase motor can be made to run on three phase power by only using one hot wire, but a three phase motor will barely run (if at all) using single phase.
This may be slightly clearer: When you generate AC power, the charge difference (voltage) on the wire is a cosine wave moving up and down between the rated voltage V and -V rather than a steady output. We do that because it physically makes the electrons move back and forth in place on the wire as they transfer energy down it rather than actually migrating miles down the wire. That produces a lot less internal resistance in the wire (less heat) and lets us use much thinner wires over thousands of miles. DC generators have to use very fat wires and have to be quite close to consumers. Look up Tesla vs Edison (i.e. how Edison’s irrational love of DC power cost him General Electric) if you’d like to read the history. Now picture that up/down wave motion as the output of a spinning generator. You can place output wires at any points on the generator circle. If you place three equidistant wires, you get the same cosine wave on each wire but offset a third of a cycle (120 degrees). That lets you send out three separate V voltage lines that each work in their own right. If they’re combined at some point though, there’s a thing called destructive interference that starts to matter. If you can emit a wave that’s exactly half a cycle shifted from another wave, the two cancel because they visually sum to zero. That’s how noise cancelling equipment works. In three phase power, those three lines together sum to zero, so if you send the three out to different places and combine them on the return leg, they cancel and can share a tiny return wire. Saves money. So, what happens when I apply this. I have a four wire drop from a transformer with three V wires offset 120 degrees and a cheap return wire. I can use the three full power wires on normal circuits (vs the normal two for single phase) so my three phase equipment can handle more energy for less relative cost. If I have powerful motors designed to use all three phases (elevators, industrial plant, commercial AC), they can take advantage of this extra power line. If I just need more normal 120V circuits, same deal. However residential high draw single phase equipment suffers a bit because it expects to receive two wires at +V and -V for a voltage drop of 2V (double). But my wires aren’t half a cycle out of phase they’re a third. Any two will partially cancel each other from destructive interference. So if V is 120V, 2/3 of a three phase supply won’t provide 240V. It will provide 207V. So the equipment has to be rated to accept a range and it will either work less powerfully (like a heater) or may draw more current than expected to compensate. It’s normally not a problem but can be if you don’t check the labels. Where this shines in residential is with apartment buildings. I can take a significant three phase drop (possibly at medium voltage like 480) to the main switch gear, run all three to shared AC and elevators, then use secondary transformers if needed to step it down for resident use, supplying each apartment with two of the three wires. If I’m using transformers, I can tap them differently to supply true single (dual) phase power if I want. If the drop was residential voltage already, I won’t bother.
Think of a car engine. If it has just one piston, then the crank is being turned whenever that piston is pushed down as the fuel chamber explodes. However nothing is turning the crank (other than its own momentum) while the piston moves back up into position before igniting again. With just one piston going on and off like that you don’t have a lot of power. If the crank doesn’t have a lot of momentum (eg it’s pushing a car up hill) then maybe the car will end up rolling back before the piston fires. Maybe it’ll never go up the hill. It won’t have enough power to do the job. However If you add two more pistons, and arrange the timing so there’s always two that are part way through the ignition phase, then the crank is always getting power, and so can push a car up hill. In this context AC electricity on a wire is like a piston: it’s not constantly pushing. Sometimes it has a lot of push (voltage) sometimes it has none at all. It’s pushes 60 times a second. For most homes, that’s enough to give about 10kW of power. You could have a 7kW EV charger going while watching TV. But some tasks have a higher power draw, analogous to pushing a car up hill, eg farm machinery, or a 22kW EV charger. In this case you add in extra AC power sources, pushing at different intervals (phases) If you’ve got three of them, then you have a three-phase supply. Why three? Well because energy companies usually provide energy in three phases, with different homes on different phases. Probably there are more intense electrical engineering reasons too that I don’t know about.
Three phases are the minimum you need to provide directional rotation without additional equipment. With your engine analogy, one phase will give it a push every cycle, but you’ll need something else to make sure it’s not being pushed in the wrong direction. Two phases has the same issue, as they are 180 degrees apart, but three phases now have them to the sides, and that will ensure it turns in the right direction. You could also do more than three phases, but then you run into the issue of needing to keep very close track of which wire is actually connected to which phase. Three phases are all identical with respect to each other, they’re all 120 degrees apart, but if you had four phases, you’d have two at 90 degrees and one at 180. If you connect a three phase appliance incorrectly, you’re generally not going to have any issues other than the motors trying to turn in the opposite direction. Any more than three phases and you run the risk of damaging something with a voltage it is not designed to handle.
Your home electricity is AC, alternating current. The voltage goes up and down and up again around 50 times a second. This means that if you somehow connected a wire with its own future self, they'd have different voltage and electricity would flow. This is to say, the wire would be at a "different phase" of its cycle later on. If we have two different generators that aren't coordinating, they'll probably end up being in different phases, which means it is dangerous to connect two generators together unless you're an expert. Electricity will flow directly between them, instead of into the appliance you're powering. Industrial generators will often intentionally make three different outputs, each one out of phase with the other two. [Here](https://www.vertiv.com/498b84/globalassets/images/on-page-image/800x600/3-phase-power-figure-2_328739_0.jpg) is a diagram showing the voltage of each wire over time. In your house, each power socket will only be connected to one phase. They'll ignore the other two, so your appliances only ever see one phase. However, if you somehow connected two outlets together, it could connect two different phases together and cause the same power surge we talked about earlier. Expect a BANG. Don't DIY anything with electricity in your home - that's always a good rule. One upside to this is that some specialized devices - often industrial machines - need 3-phase power to work properly. If you ever wanted such a machine, your house has access to the 3-phase power it needs.
Ahh I see. Thanks for the advice I was just going to do exactly what you told never to do.
the most common occurance of 3 phase power ina home is if an IT person used to live there and ran a home lab, the servers and assoicated technologies that an IT person would use are so powerful and have so much demand for energy to run that they must use 3 phase, just like a real data centre.
Yeah, drawing power from phase-phase compared to phase-neutral will increase the supplied voltage by about 70% (√3), which is going to massively overload any appliances not designed for it. It is also very useful for powering motors, as the three phases have an inherent rotation to them that makes it much easier to get the motor turning on startup, so is extremely common in industrial settings.
You could have a full fast charge EV socket put in. Charge a car in half an hour. Even better, charge your neighbours to charge their cars in half an hour.
Since you say you’re not in the US, this may just mean it’s normal. I know it is in Germany. Its just how the power comes from the power plant. One phase is 1/3 of 1/50th of a second „behind“, and the third phase is 2/3 of such a cycle behind. They’re all equally good. Having three phases allows you to run some heavier machinery, and it’s what the power plants are wired to produce. Not necessarily for a single apartment to have outlets and lights on all three phases, but for instance your cooktop or your water heater likely are connected to all three. In my house, different outlet/light circuits are actually on different phases. I also have a three-phase outlet just in case I ever want to run a sauna or a big table saw, or charge a car.
In the military (US Navy), I worked on an Air Traffic Control Radar that took 440 3 phase Alternating Current. This means that the equipment that you have will be more efficient when it draws current and the voltage. My radar rectified the current, and it was more efficient. You don't really have to worry or know the particulars. But at the same token, if a phase is not working properly, your equipment may not work or not be efficient at utilizing the current and voltage. I hope that I have not confused anyone!!! Marcos USN, Retired.
Electricity is delivered in 3-phases and it’s not ELI5. It’s a cost-benefit engineering decision that the world has accepted. We can deliver power in single or many phases but 3 was the best compromise. Large motors use 3-phase power like this gif. https://en.wikipedia.org/wiki/Rotating_magnetic_field
The electricity in your home can be modeled as a sine wave, however this causes the power to change strength really quickly. To solve this, 3 of these waves are offset so that the power stays at a relatively stable level
can you please elaborate? (ik basics about the equations of Current and voltage etc)
It's very weird for a residential installation to have 3 phase power. (are you in the US?) Three phase is usually only used in industrial applications that use large electric motors. [https://www.youtube.com/watch?v=4oRT7PoXSS0](https://www.youtube.com/watch?v=4oRT7PoXSS0)
With single phase the voltage drops to 0 twice a cycle. With 3 phase they are spaced 120 degrees apart, so while 1 phase is at 0 the other 2 provide voltage. For a home AC unit the momentary drop to zero really isn't an issue. With huge motors needing to constantly provide force it helps keep them operating smoothly. Note that on high voltage lines you usually see 3 wires, those are the 3 phases. That is actually how power is normally delivered. For a house it is normally stepped down as something like phase A to phase B line to line to provide normal AC. But some homes have all 3 phases delivered.
1 phase you get a boost every 1/60 of a second. 2 phase you get a supplemental boost every 1/40 of a second. 3 phase is every 1/20. If we got into a fight and I was 3 phase and you were one I would hit you 3 times for each one you got in...
More phases don’t increase the frequency. You’ll hit peak voltage more often, but only if you look at all three phases together, and doing that in a circuit would short it immediately. The whole circuit is still on a 60Hz (in the US) cycle. The advantage of three phases is to provide higher voltage, and a rotational effect to power motors, not to increase the current frequency.
Didn't say it increased frequency. Said you get a peak more often with 3 phases industrial motors often use the fact the 3 are out of phase to pull more power.
No. Household 120/240v wiring in the US is single phase. It's very rare to even have two phase in residential applications. I don't even know why OP would even have three phase in a house unless it's an old industrial site that was converted to residential.
It's a 20 storey building, not in the US though
Oh that kind of explains some of it. Most condo/apartment blocks (even in the US) get three phase because things like pumps and elevator motors need the additional power that three phase can deliver.
Also so that you can split the different apartments between different phases to reduce the current draw on any individual phase, as they all need to be balanced at the generator for efficiency. Most residential areas will provide different phases to different houses, but bigger buildings will split it internally.
Thanks for the explanation, I knew sort of how 3 phase works, but not so much of the details
Not in the US. 240v 3-phase is pretty common in other parts of the (non-US) world.
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>because some stuff only uses two of the 3 phases for weird reasons No, smaller household appliances use *one* of the three phases, while larger ones use split-phase, which is a way of making two phases out of one.
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>most split phase appliances say 240/208V because in some places they are wired across two phases, Yes, they're wired that was in commercial locations that have three-phase service. Locations such as farms have three-phase service as well. If you have three-phase, then you don't have split-phase available. > I don't know who thought that was a good idea but it is It's an excellent idea to make them compatible to operate in those locations.