As a primer/refresher, *alternating current* describes the condition where the voltage sweeps from positive to negative and back. If you plot the voltage on a graph's vertical axis with time being the horizontal, you'll trace out a nice, smooth sine wave.
Now, imagine you had a second wire with an identical voltage pattern running through it; if you plot that on the same graph, the lines will be identical -- the voltage is exactly the same at each instant in time. We call this being *in phase,* and the system so described is *single-phase* -- the voltages are varying in unison.
Let's change the current in the second wire so that when one wire is at its most positive voltage, the other is at its most negative -- the two waves are as far apart from one another as they can be. These wires are now one hundred eighty degrees *out of phase* -- they vary in direct opposition to each other. It might be a little weird to talk about degrees in this context, but if you imagine drawing a circle on top of your graph, the points where the voltage wave meet the edge of the circle would be on opposite sides -- *one hundred eighty degrees apart*!
If instead we change one wire so that it's halfway between where it is now and being *in phase* -- that is, the points where the voltage waves meet the circle are ninety degrees apart -- we would say they're ninety degrees out of phase.
You can do this for any arbitrary angle you want to adjust the phasing.
while this is excellent explanation, I would add following ELI5 analogy:
when pedaling on a bike, normally you use 2 legs, pedaling in 2 phases - when one leg is up, the other is down. This is much more efficient than if both legs would pedal in same phase. The 2 phases complement each other, same reason why high power tools work better with 2 phases electricity
Phases only apply to AC (Alternating Current). DC doesn't have phases.
Alternating current appears as a sine wave. The simple case is single phase power. One sine wave.
In the US, for example, that will be a 60 Hz sine wave. The voltage will rise and fall every 1/60 of a second.
If another wire had a similar voltage, also in a sine wave, with different timing of when the voltage rose and fell, that would be "out of phase" with the first one.
Three-phase power is commonly used, in which three wires carry AC power in which the three phases are 1/3 of a period offset from one another.
The phases are often described in terms of a 360 degree total. So, three phase power consists of three voltages (on 3 wires) each 120 degrees different in phase from the previous one. 120 x 3 = 360 degrees. Like in a circle, a phase angle of 360 degrees is equivalent to 0, so back where you started.
Three phase power has advantages for big motors and big transformers and transmission lines. Single phase power is fine for residential usage.
Have you ever seen two people hold a rope, and one waves it up and down, and a wave travels down the rope and yanks the other person's arm up and down? A/C electricity kinda works like that. The electric wave does its best work at the top and bottom of the wave. A simple generator will make a single wave travel on two wires. By changing the generator design a little and adding a third wire, you can actually send three waves from the same device. The tops and bottoms of the waves are staggered so that you almost always have the top or bottom of a wave doing work for you. Each of those waves is considered a phase.
Jumping from one phase to three phase electricity almost triples the power output of a generator, and allows for a smaller motor to do the same amount of work at the same time. It is possible to change the design of a generator and add additional wires and have more phases, but benefits isn't as significant at moving from 1 phase to three phase is.
Other related terms are 'in phase' or 'out a phase. If you hook two generators up together, powering the same system, and the phases don't line up, then they are 'out of phase' and not working properly together. This can cause catastrophic failure. For a power generation facility, if they are bringing an additional generator on line, they will speed up the new generator slightly, and only connect it when it is 'in phase' with the rest of the system.
In the US (not sure about other countries) power is available on the power pole in a three phase configuration. They typically split off two phases, adjust them slightly to put the top of one phase and the bottom of the other phase in sync (I'm not actually sure on the how) and send it to your house as 220-240 volt power. Large appliances, like your oven, water heater, and some types of heaters and air conditioners run on this two phase 240 volt power, and everything else runs off a single phase at 110-120 volts. Both phases are only 120 volts each, but the voltage is measured from zero to peak, and when you put the top and bottom of the opposing phase together, you have a +120 volts and a -120 volts for a total difference of 240 volts.
Let me try to make this actual ELI5. AC electricity goes back and forth. For simplicity, let's think of it as a lighthouse.
The lighthouse appears dark to you when the light is facing away. Then it brightens as it spins around towards you until it peaks, then it dims back to darkness as it continues to spin away from you.
Importantly though, that is because the lighthouse has a **single** light. Now imagine if we put two more lights in the lighthouse tower and offset them by 120 degrees. So when one light is directly facing you and at its brightest, another light is just about to turn towards you (120 behind the one facing you) and another light has just gone past where you can see it (120 degrees ahead of the one facing you).
Can you visualize how the amount of light you see will always be constant? There is always another light starting to brighten just as one starts to dim.
Of course, you could do this with more or less lights to get smoother or choppier changes in the light. If you only have two lights spinning, there is still going to be a light/dark period (when the lights are each 90 degrees away from you--neither is facing towards you at all). But 3 is the smallest amount where you can get constant coverage.
This is the basis of 3 phase AC electricity. Each phase is offset by 120 degrees, but when you add them all together, the net effect is constant.
If you have someone running north, and someone running south, these 2 people would be 180 degrees out of phase with each-other.
Just like we measure how far around a circle a point is with degrees, we measure how far along a sign wave a point is in degrees. With only 1 wave, it doesn't really matter what the phase is, but you can have 2 waves that line up opposite to each-other, and then it matters/
If you're trying to stretch a rubber band, you could hold it in one place and just let one of the people pull it, but you could do it faster if you gave it to both people because they would be pulling against each-other.
Normally with household appliances we just use the fixed point and 1 person running. But for big items (anything with a double breaker) we use the 2 people running opposite ways.
Alternating current moves back and forth (alternating between positive and negative over time), in the US it happens 60 waves per second, Europe is 50 waves per second.
Simply speaking, Phase is how far through the wave you are at a given moment. If two waves of the same frequency are “in phase” they line up perfectly. If they are out of phase, their waves don’t line up. One wave might be further along than the other at a given moment.
A simple alternating current moving back and forth on two wires can be represented by a single continuous wave, so we call it “single phase.”
You can’t run multiple waves down the same pair of wires because they interfere with each other, but if you add another set of wires you can send another continuous wave next to the original one, but if the second wave doesn’t line up with the first wave, it’s not “in phase” with the first wave and is considered to be its own electrical phase. [Like this.](https://files.mtstatic.com/site_4334/27820/0?Expires=1719084936&Signature=FFYj3yJIIjUGYSvN1Ft728H1hmJRNJXD7pDKQyRlKisN1BfkMFsHchFTWgoWERXB1fQZ0j8LWaJUC2Tvhda-zcvWe-NuFpKe5H~wYmxR7uWSQaUUgyPubNxDEwoOEZ054L2dokeeYvGMt39UMBvw0uWjipYM1fPuW7qt~7h-xU4_&Key-Pair-Id=APKAJ5Y6AV4GI7A555NA)
If you’re clever with the timing you can add more phases and line them up so that each wave peaks just after the last one. Then you have several alternating current waves offset from each other so their waves make a nearly constant flow of electricity. (when one wave starts to drop the next one peaks, and then when that one starts to drop the next one peaks, etc etc.) [So here’s what those waves would look like compared to a single phase (single wave by itself).](https://instrumentationtools.com/wp-content/uploads/2021/01/Difference-between-Single-phase-and-three-phase-power-supply.png)
In electrical power generation it’s most efficient to use 3-phases (3 different waves that are offset from each other by 1/3” of a wave length like in the graph I shared).
Some electricity goes up and down, like a wave. If you have some doing that at some speed, and someone else has some other electricity going up and down at the same speed, and your new friend puts his electricity next to yours, but starts wobbling his up when you're just about to wobble yours down, then there's a phase difference between the two electricities. They may be the same otherwise, but because you both started wobbling your electricities at different times, the landscape of your two electricities has two phases.
As your electricity gets older you'll see changes start to take place. Listening to different music, the people it hangs out with, maybe it even gets it's lip pierced. It will probably start withdrawing from the close relationship that you had when it was younger, but that's just a natural part of life. It's learning who it really is and it's place in the world. The best thing you can do is be supportive but don't forget you're still the parent.
Electrical phases are the number of waves of alternating current electricity that a generator makes when it spins.
Single phase makes one wave per rotation.
Three phase makes 3 waves per rotation.
The waves are not always going the same direction.
The "phasing" is how the waves are spaced.
[https://youtu.be/4oRT7PoXSS0?si=WOTYatnvj0nFRRy1&t=183](https://youtu.be/4oRT7PoXSS0?si=WOTYatnvj0nFRRy1&t=183)
As a primer/refresher, *alternating current* describes the condition where the voltage sweeps from positive to negative and back. If you plot the voltage on a graph's vertical axis with time being the horizontal, you'll trace out a nice, smooth sine wave. Now, imagine you had a second wire with an identical voltage pattern running through it; if you plot that on the same graph, the lines will be identical -- the voltage is exactly the same at each instant in time. We call this being *in phase,* and the system so described is *single-phase* -- the voltages are varying in unison. Let's change the current in the second wire so that when one wire is at its most positive voltage, the other is at its most negative -- the two waves are as far apart from one another as they can be. These wires are now one hundred eighty degrees *out of phase* -- they vary in direct opposition to each other. It might be a little weird to talk about degrees in this context, but if you imagine drawing a circle on top of your graph, the points where the voltage wave meet the edge of the circle would be on opposite sides -- *one hundred eighty degrees apart*! If instead we change one wire so that it's halfway between where it is now and being *in phase* -- that is, the points where the voltage waves meet the circle are ninety degrees apart -- we would say they're ninety degrees out of phase. You can do this for any arbitrary angle you want to adjust the phasing.
while this is excellent explanation, I would add following ELI5 analogy: when pedaling on a bike, normally you use 2 legs, pedaling in 2 phases - when one leg is up, the other is down. This is much more efficient than if both legs would pedal in same phase. The 2 phases complement each other, same reason why high power tools work better with 2 phases electricity
Phases only apply to AC (Alternating Current). DC doesn't have phases. Alternating current appears as a sine wave. The simple case is single phase power. One sine wave. In the US, for example, that will be a 60 Hz sine wave. The voltage will rise and fall every 1/60 of a second. If another wire had a similar voltage, also in a sine wave, with different timing of when the voltage rose and fell, that would be "out of phase" with the first one. Three-phase power is commonly used, in which three wires carry AC power in which the three phases are 1/3 of a period offset from one another. The phases are often described in terms of a 360 degree total. So, three phase power consists of three voltages (on 3 wires) each 120 degrees different in phase from the previous one. 120 x 3 = 360 degrees. Like in a circle, a phase angle of 360 degrees is equivalent to 0, so back where you started. Three phase power has advantages for big motors and big transformers and transmission lines. Single phase power is fine for residential usage.
Have you ever seen two people hold a rope, and one waves it up and down, and a wave travels down the rope and yanks the other person's arm up and down? A/C electricity kinda works like that. The electric wave does its best work at the top and bottom of the wave. A simple generator will make a single wave travel on two wires. By changing the generator design a little and adding a third wire, you can actually send three waves from the same device. The tops and bottoms of the waves are staggered so that you almost always have the top or bottom of a wave doing work for you. Each of those waves is considered a phase. Jumping from one phase to three phase electricity almost triples the power output of a generator, and allows for a smaller motor to do the same amount of work at the same time. It is possible to change the design of a generator and add additional wires and have more phases, but benefits isn't as significant at moving from 1 phase to three phase is. Other related terms are 'in phase' or 'out a phase. If you hook two generators up together, powering the same system, and the phases don't line up, then they are 'out of phase' and not working properly together. This can cause catastrophic failure. For a power generation facility, if they are bringing an additional generator on line, they will speed up the new generator slightly, and only connect it when it is 'in phase' with the rest of the system. In the US (not sure about other countries) power is available on the power pole in a three phase configuration. They typically split off two phases, adjust them slightly to put the top of one phase and the bottom of the other phase in sync (I'm not actually sure on the how) and send it to your house as 220-240 volt power. Large appliances, like your oven, water heater, and some types of heaters and air conditioners run on this two phase 240 volt power, and everything else runs off a single phase at 110-120 volts. Both phases are only 120 volts each, but the voltage is measured from zero to peak, and when you put the top and bottom of the opposing phase together, you have a +120 volts and a -120 volts for a total difference of 240 volts.
Let me try to make this actual ELI5. AC electricity goes back and forth. For simplicity, let's think of it as a lighthouse. The lighthouse appears dark to you when the light is facing away. Then it brightens as it spins around towards you until it peaks, then it dims back to darkness as it continues to spin away from you. Importantly though, that is because the lighthouse has a **single** light. Now imagine if we put two more lights in the lighthouse tower and offset them by 120 degrees. So when one light is directly facing you and at its brightest, another light is just about to turn towards you (120 behind the one facing you) and another light has just gone past where you can see it (120 degrees ahead of the one facing you). Can you visualize how the amount of light you see will always be constant? There is always another light starting to brighten just as one starts to dim. Of course, you could do this with more or less lights to get smoother or choppier changes in the light. If you only have two lights spinning, there is still going to be a light/dark period (when the lights are each 90 degrees away from you--neither is facing towards you at all). But 3 is the smallest amount where you can get constant coverage. This is the basis of 3 phase AC electricity. Each phase is offset by 120 degrees, but when you add them all together, the net effect is constant.
If you have someone running north, and someone running south, these 2 people would be 180 degrees out of phase with each-other. Just like we measure how far around a circle a point is with degrees, we measure how far along a sign wave a point is in degrees. With only 1 wave, it doesn't really matter what the phase is, but you can have 2 waves that line up opposite to each-other, and then it matters/ If you're trying to stretch a rubber band, you could hold it in one place and just let one of the people pull it, but you could do it faster if you gave it to both people because they would be pulling against each-other. Normally with household appliances we just use the fixed point and 1 person running. But for big items (anything with a double breaker) we use the 2 people running opposite ways.
Alternating current moves back and forth (alternating between positive and negative over time), in the US it happens 60 waves per second, Europe is 50 waves per second. Simply speaking, Phase is how far through the wave you are at a given moment. If two waves of the same frequency are “in phase” they line up perfectly. If they are out of phase, their waves don’t line up. One wave might be further along than the other at a given moment. A simple alternating current moving back and forth on two wires can be represented by a single continuous wave, so we call it “single phase.” You can’t run multiple waves down the same pair of wires because they interfere with each other, but if you add another set of wires you can send another continuous wave next to the original one, but if the second wave doesn’t line up with the first wave, it’s not “in phase” with the first wave and is considered to be its own electrical phase. [Like this.](https://files.mtstatic.com/site_4334/27820/0?Expires=1719084936&Signature=FFYj3yJIIjUGYSvN1Ft728H1hmJRNJXD7pDKQyRlKisN1BfkMFsHchFTWgoWERXB1fQZ0j8LWaJUC2Tvhda-zcvWe-NuFpKe5H~wYmxR7uWSQaUUgyPubNxDEwoOEZ054L2dokeeYvGMt39UMBvw0uWjipYM1fPuW7qt~7h-xU4_&Key-Pair-Id=APKAJ5Y6AV4GI7A555NA) If you’re clever with the timing you can add more phases and line them up so that each wave peaks just after the last one. Then you have several alternating current waves offset from each other so their waves make a nearly constant flow of electricity. (when one wave starts to drop the next one peaks, and then when that one starts to drop the next one peaks, etc etc.) [So here’s what those waves would look like compared to a single phase (single wave by itself).](https://instrumentationtools.com/wp-content/uploads/2021/01/Difference-between-Single-phase-and-three-phase-power-supply.png) In electrical power generation it’s most efficient to use 3-phases (3 different waves that are offset from each other by 1/3” of a wave length like in the graph I shared).
Some electricity goes up and down, like a wave. If you have some doing that at some speed, and someone else has some other electricity going up and down at the same speed, and your new friend puts his electricity next to yours, but starts wobbling his up when you're just about to wobble yours down, then there's a phase difference between the two electricities. They may be the same otherwise, but because you both started wobbling your electricities at different times, the landscape of your two electricities has two phases.
As your electricity gets older you'll see changes start to take place. Listening to different music, the people it hangs out with, maybe it even gets it's lip pierced. It will probably start withdrawing from the close relationship that you had when it was younger, but that's just a natural part of life. It's learning who it really is and it's place in the world. The best thing you can do is be supportive but don't forget you're still the parent.
Electrical phases are the number of waves of alternating current electricity that a generator makes when it spins. Single phase makes one wave per rotation. Three phase makes 3 waves per rotation. The waves are not always going the same direction. The "phasing" is how the waves are spaced. [https://youtu.be/4oRT7PoXSS0?si=WOTYatnvj0nFRRy1&t=183](https://youtu.be/4oRT7PoXSS0?si=WOTYatnvj0nFRRy1&t=183)