How 3 Phase Power works: why 3 phases? 

Question for you guys. This video mainly features north american standard which is convenient since I am located there. But do you create another version of that video for Europeans with more prevalent European standards? Just curious. Great job BTW

Whenever you need massive smoth dc, running a delta wye and a wye wye going through a full wave bridge gives very smooth output, minimizing need for big choke coil.

Would e.g a 6 phase generator waste less energy into thermal energy? Like I wonder with our energy demands (e.g electric cars and like appliances that consumed insignificant power now kinda increased noticeably e.g a GPU can easily consume about 600watthours on its own if not more and that's without calculating the inefficiency of the PSU pulling power from the grid in order to provide 600watts to the GPU )

If the Earth's core is just a big magnet, could we put huge rotating stators in orbit around the Earth and create energy?

@@me1970 no if earth's core had a strong enough mgnetic field to produce power by spinning around a huge stator ring miles outside of the earth (which we wouldbt be able to put in orbit in the first place but lets ignore that) then you wouldnt be able to pick anything that had the slightest piece of metal on it simply because earth would pull it down towards its core ... you know like magnets do.. earths core has a magnetic field but only strong enough for us to detect with compasses or sensors not strong enough to actually have some real "pull" or magnetic intensity.

Have a job vacancy? 😅

@@haikaldaniel3790 Lol sorry no, the fat cats are freaking out because our profits are not matching Covid year gains. We sell home improvement products and covid was a huge boost in sales for us. Now that it is back to normal they feel they are 'losing money'. Greedy idiots. I have 2 months to retirement...

thanks for making me feel more stupider... if that's even a word...

Yeah, where was this guy when I was first learning this stuff almost 30 years ago. He just explained it in seconds like it's nothing. My instructors made it so complicated and confusing.

I was industrial electrician as well, and already understood how 3 phase works, most people cant wrap their head around it, but I have an electronics engineering degree, and we got deep into the math . I still learned a lot , as I was curious as to why not more with 4 or 5 phases.

in the intro it completely overlooks the fact that 230VAC systems exist. I.E. in Europe and parts of Asia...

@@TheExileFox who cares. the principles are identical and he addresses it later in the video.

@@billwall267 I care

@@UmVtCg no you don't

Same!

😂 😂😂

😂😂😂

When that happens don't worry .....it's just a phase

Seeya tomorrow!

Good luck using it tho

As an ordinary person This video is still hard to understand 😂

Three phases is the fewest number of phases whose average power is a constant. That’s why three phase electricity versus four, five, six… phases.

@@dane1234abc1 Not exactly. Three phase is the most economical for starting, (rotating) and running electric motors. No extra equipment is needed to make it work.

Three phases was chosen because it creates the most economic rotating magnetic fields to start and run other motors. Single phase needs extra equipment.

Glad to hear, hope it helps with your studies. If you can share links to your class mates so we help even more people that would be much appreciated

@@EngineeringMindset A great video, particularly the explanation of RMS. One important point about 3 phase that you did not mention was that simply reversing 2 wires reverses the direction of rotation of a motor. This is vital for lifts and escalators, as well a useful in machine shops. Another, less important point was that in HV distribution, one phase is bonded to ground, making emergency tripping simpler. If they are not available already, a video on current transformer use in metering would be great, as well as a video on PAM wound motors having 2 adjacent pole asynchronous speeds. 4 to 6 pole is very useful in refrigeration compressors since it produces ideal torques. The 4 pole speed is ideal for use in temperature pull down.

​@@EngineeringMindset love you man

You mean FOOOL

- Mehdi Sadaghdar

Exactly, video about it here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RiRyzLl4Y8U.html

@@EngineeringMindset you did not get the reference did you lol

Electroboom have set a standard here, albeit unofficial. 😄

Yes... The extra phases (e.g., six-phase) from the power source can be used to cancel out very objectionable low order load harmonic currents often associated with the rectifier type loads that you describe.

Generally acheived by adding a transformer with multiple secondaries that can be combined to phase-shift the winding voltages, so you supply 12-pulse or 18-pulse rectifiers. This reduces the harmonic currents on the supply side, and is commonly used on medium-voltage inverter drives to reduce the stress on the motor insulation and provide a lower harmonic voltage waveform

One could also use a 3 ph motor to drive a generator/ alternator of choice, for those localized requirements.

Also 400 cycle for high power electronics.

​@@warrenpuckett4203And civil aircraft

Thank for writing this for all of us =)

It would still vary in real life due to magnetic saturation, shape of the magnetic field and so much more tho, that's why 5 phase motor exists

Retired EE here... snarfsnarf's comment is right on! The instantaneous sum of the three sine-squared phase power waveforms (displaced 120 degrees) add up to a constant value flat line with no ripple for balanced passive loads. Some specialized non-linear loads like large rectifiers can benefit from greater than three-phase power sources. For example, a six phase source can cancel otherwise objectionable low-order harmonics in the rectifier's load currents, specifically the 5th and 7th harmonic currents.

At 6 phases, it will be a better electric motor and / or generator. Due to the fact that 6 phases provide different efficiencies depending on the use, with that said, 3 phases is not that efficient at constant use. Look at all the 3 phase EV'S they suck big time due to them using 100kwh ++ batteries that's equal to a 120kw + generator due to the losses at full load.. Just saying 3 phases suck literally 😂😅😂😅

@@MA-is5hh 2015 Study showed that 6-phase was 1-1.74x better in terms of power transmission than 3-phase. It literally is better, 3-phase is cheap and basic compared to the returns of 6-phase. There is no mathematical limit, only an engineering limit.

I'd advise against passing this one. Electricians themselves, and in fact most instructors, are not themselves qualified to understand how non-electricians might grasp certain basic concepts. The reason for this is simple: you already understand them. You've lost the power to see where people lose the train of ideas. I recommend you find several beginners and learn by showing the video and watching and asking where they lose what makes sense. Ask pertinent questions at certain times, like after 3:00, can your student explain electron flow directionality through a wire at forward and reverse sine phase? I suspect most will not, because the video glosses over this.

I don’t but this is fascinating 😅.

It's 2:45 am. I also have an EE degree. Wtf are we doing.

😂

It’s fun to watch and you want to hear someone try a dnteach what you know so well. 😁

@@burnte I'm a pulsed power EE. I haven't touched 3 phase since college 🤣 from what I remember this is a great explanation

So, I don't know engines very well (EE here) but the voltage induced in AC due to a rotor's magnetic flux is kind of like firing pistons at different angles: most efficient when fired at max piston height. Firing a piston when a piston has provided less compression to the air/gas mixture will provide less force to the crankshaft. This is similar to how a rotor magnetic field will induce less voltage when the rotor field is not at a maximum when "cutting" a stator winding in a generator.

And without clogging an exhausted brain with endless formulas, as is done in university.

Absolutely, we covered in detail in our previous video here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-u0SsejDCVkU.html

347/600V is actually commonly used instead of 277/480V in Canada

My apartment even has a shared neutral because of that. It allows you to cut down on the copper required by about a quarter as you're not duplicating the neutral. So, one hot from one phase and another from the other and both of them using the same neutral. It works, but it can be annoying for some things you might want to wire in.

👍 split single phase

3 phase 480 isn't all that rare. Just about all manufacturers have 3 phase 480 systems. Canada uses 600V systems.

Absolutely, we covered it in great detail with step by step math in our last video here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-u0SsejDCVkU.html

If he understood the equations he'd know that both 2 and 3 phase systems deliver constant power.

@@Ryrzard What do you mean by constant power? Wouldn't a resistive heater still flicker?

​@@user-cm4wd1sn8d A 3 phase heater has at least 3 heating elements and while individual element will flicker, the sum of their heat outputs will be a constant without pulsation. That's assuming that they are purely resistive. Heaters, especially high temperature filaments, are not linear devices and their resistance changes with temperature and as a result, they produce some harmonics in the current, some of which would not be canceled out by 3 phase current. But generally speaking, 3 phase power provides constant power for linear loads ("dumb" devices).

Are we talking about the difference between three out of phase and three in phase resistors, for the purpose of producing the same HEAT? Is there any scenario where IR being pulsed above a handful of Hz will make a difference? Heat diffusion in whatever absorbs it is slow and _averagy_ !

@@Trombonauta While resistive heaters have their thermal inertia to smooth their output, the constant aspect is critical for big generators and inverters, as well as big industrial loads like motors. But even at a small home that has a 3 phase motors powering a heat pump or AC it's beneficial because the constant power and lack of pulsation decreases wear and noise.

Yugoslavia doesn't exist anymore. Is Serbia, Croatia, Montenegro, Slovenia, Macedonia and Bosnia- Herzegovina. In which year you live? As of 1991 SFR Yugoslavia ceased to exist.

@@UncleHo5 Does it really matter? It is all the same...

@@Mladjasmilic for me not. But you can ask a Croatian. And you as far as I can see you are denying the present realities. I m not from any of the above country but this is the history. And... subject is closed from my side.

@@UncleHo5 In Slavic, Jug (Yug) means 'south' and Slavia 'land of Slavs' . So term Yugoslavia still refences not only the country, but also the whole region where south Slavs live. And, no, it does not include Bulgaria, as Bulgarian are Slavic speaking Bulgars, Turkic people, like Yiddish is term for German-speaking Jews. There are also terms like ex-Yu, Yugosphere, West Balkan, etc. As for language, standard Croatian, Bosnian, Serbian and Montenegrin are so similar, that there are maybe 50 words in everyday speak which are different. Macedonian and Slovene not so much. But Croatia has a problem with Yugoslavia, that is true. Few days ago they arrested members of 'Bijelo Dugme', a rock band from '70s and '80s for singing songs which have term 'Yugoslavia' in Lyrics.

@@Mladjasmilic Thank you for this info, I was curious to understand this part of the world more, unlike the other person who replied to you...

that is actually a 4-phase motor.

@@andrewgrillet5835 Nope. Two-phase, 4-wire.

I thought constant would be DC? AC no matter what is bouncing back and forth.

​@runnergo1398 DC just means the voltage never changes sign. If the voltage is constant, it will also be constant power, but constant power does not imply constant voltage, and multiphase AC can also deliver constant power.

@runnergo1398 For balanced three phase AC, the SUM of the pulsating instantaneous power in each phase adds up to a constant value... It's fortuitously just how the trigger works out... It also means the the instantaneous torque that must be delivered to the generator shaft by the prime mover (e.g., the turbine) is also constant, not pulsating.

Car headlights, Christmas lights, and the aforementioned cheap bulbs. There's no end to the flickering

The old florescents flickered so fast you couldn't tell unless they were wearing out

There's several reasons for this, one is the alternating current and a cheap power supply. Another is that leds are often dimmed with pulse-width modulation, which isn't bad in principle, but often the pwm speed is too slow and causes a visible flicker. With car headlights that effect becomes super obvious if you see them in a mirror.

Even a lot of pricier LED bulbs flicker but at a much higher frequency

@@kendokaaa Every LED flickers on AC. But yes, properly build ones flicker in the range of kHz. There are cheap (and expensive) ones that flicker in "low" frequencies that you can easily detect with your smartphone - those should not be used. And there are cheap (and expensive) ones that do it properly.

Thank you for your support. I hope your dad enjoys his gift.

3 phases is the number of phases which was found to deliver the most power to devices without having to engineer in safeguards to keep the system viable. No one has demonstrated that adding more phases is economical and safe.

agreed, ive been scrubbing through looking for the "why not 2" and im not really seeing it. And in the comments, i learned it's because a Harley motor shakes a lot :shrug:

Mikhail Dolivo-Dobrovolsky invented 3 phase generator , 3 phase transformer and induction motor , in Germany 1890s. Same time in Sweden, Jonas Wenström received in 1890 a Swedish patent for same 3 phase system, that was start of ASEA, that is now part of ABB. Nikola Tesla in USA and John Hopkinson in UK, also came in conclusion that 3 phase system had something. So you had 4 men in 4 different countries that all came to same end result, 3 phase AC system, with practical experiments.

I worked on a system that used 9 phases, 200v, roughly 1000hz per phase.

In the USA, you can have 3 phase at your house, but the cost varies significantly depending on the power lines and the distance to your house. For example, my parent's house has a power line with all 3 phases right in front of the house, so the installation cost would be low. However, in my neighborhood, they run 3 phase down the main street, and only branch a single phase down each side street. So I'd have to pay for them to add two phases down half a mile of road - much more expensive. And if you live somewhere with underground power lines? The cost would be insane.

Anything newly built in the last two decades in NL already has three phase as default in the "meterkast"

​@@MichielKlaverThe wiring is there but it's not hooked up by default though, as far as I know 🤔

@@pyramidsinegypt the new hosing projects I've visited the past 10-15 years all had 3-phase main breakers. Probably the heat-pumps are to blame

@@MichielKlaver Ah yeah, I think you're right.

Tesla oroginally used a 2 phase 4 wire system and it can still be found in Philadelphia and Connecticut. A Scott transformer can transfer 3 phase into 2 phase 90 degrees from each oter or vica versa. You confused cable with wire.

I love a succinct Chinese meal.

That sounds similar to what we have in Sweden, (and no, we are not the same country :)) As far as i know, anything other than 3-phase 230/400v is non existent. Just curious, what is the what is the fixed cost for an electric connection in Switzerland? Our model is so far that we pay a fixed cost monthly for 16A main fuses, 20A and 25A is also common. (and on top of that the price of each kWh of course).

Sounds a little dangerous, but can use much smaller copper wires and reduce cist.

@@Sam2sham why would that be dangerous? ever been to Switzerland? here is everything up to code and security is taken extremely serious

@@Superbus753 just the extreme voltage.

@@Sam2sham with the safety culture here thats not a problem. Also every house hets regularly inspected and all electrical installations testet. These inspectors are thorough and don’t miss the slightest difference from code or problem.

Who knew Goldilocks was an electrical engineer?

@@eyerollthereforeiam1709 Maybe she was just going through a phase...

@@PunmasterSTP GROAN! You truly deserve your screen name.

@@eyerollthereforeiam1709 Just let me know if you ever want to hear a pun on a particular topic 👍

The American one looks crazy, so may different voltages.

This is sort of wrong. Usually you have 1 substation (lets say it steps it down from the big transmission lines to 1200V) feeding a town of anywhere from 10,000-20,000. From there it it gets further stepped down on the pole to 120/240 split single phase as most of the grid is designed to be residential load based. Transformers are spaced out every 5-6 poles as step-up transformers to try and keep the secondaries on the poles at a constant voltage. Also the primary sides of the transformers on the poles are fused. In the event of a short or overload on the secondaries of the pole transformers, the utility expects the transformer to blowup as the fuse which in turn would blow the primary side fuse (though this does take a big short/overcurrent and time to cause). Also most substations are equipped with circuit breakers in the event the secondaires out of the substation were to short out. In terms of a Commercial application, the building gets its own transformer as seen in this video due to its needed a 3-phase hookup of either 120/208 or 480/277 depending on the loads the space needs (also the video does fail to show that 277V lighting is a thing). The only time a house would get its own transformer is for one of 2 reasons. The first reason is that is a higher amperage house than normal (higher than 200-300 AMPS). This results in the utility either giving the house its own transformer on the pole or having a transformer installed on the persons property. The other reason occurs when you get to the low population density areas where houses are easily a .25mile to .5mile apart and it is not feasible to have a step-up transformer every 5-6 poles.

Thank you, glad it was useful and thank you for your support, I hope you enjoy them, much appreciated. Send a photo in, maybe we can publish it. Not sure how long you've been a subscriber, but just incase you missed it, we have also covered car alternators, car batteries and starter motors in previous videos along with differentials too!

Not really, it wasn't an arbitrary choice. 3 is the minimum number of phases to supply constant power to a passive load (e.g. motor or heater). Any multiple of 3 (6, 9. 12-phase!) would do the same but going to 6 or 9 phases would give no advantage.

@@snarfsnarfs That's what I said... BTW, 3 phases do not supply constant power, the power still drops, but not that much to cause instabilities in mechanical outputs.

@@gabrielbarrantes6946 in an ideal system the power doesn't drop at all. It is constant power all the way through the cycle. As the instantaneous power from the 1st phase starts to drop, the other 2 phases start to deliver that power in the exact proportion that the sum total stays constant. For circuits containing active components it's different, but for passives like motors/heaters/etc the sum total stays constant through the cycle.

@@snarfsnarfs 2 phases shifted by 90° also show constant power. But then you need 4 wires (two separate phases) or 3 wires (one common to both phases). The current in the common wire is sqrt(2) higher, so a thicker wire is needed. But if you need 3 wires anyway, a three phase system is the optimal solution. as then the current in the common wire is zero and this wire can be omitted. Anyway: you are perfectly right: power is constant in an ideal system, while in the video is said: in an ideal system power still varies a little.

@@user-fl5nv7oh3z That's a really good point. 😀 In the 3phase case we have: p1+p2+p3 = sin^2(x) + sin^2(x + 2×π/3) + sin^2(x - 2×π/3) = 1.5 In the 2phase case it's also constant as you said: p1+p2 = sin^2(x) + sin^2(x + π/2) = 1 I never really thought of it like that before. As you said it still ends up requiring an extra wire (or a thicker common wire) than the 3ph case anyway. Thanks for raising the interesting point. 😀

LOL, no...

I have literally no experience in this, but I’m curious as to why it would be out of phase there. The highlighted area under the curve shows the wave to be at 0 when the magnet is parallel to the coil. Would that not be the case? From someone with no experience that seems correct, but If it’s wrong I’d be interested to know why.

Relax bud. This isn't a video on how to read oscilloscopes. Also, you're holding your phone sideways so you're 90 degrees out of phase

​@@nickdowning5562it's not off phase. When the negative is facing the coils the dot should hit the peak of the negative wave

​@@AfricanLionBat it is wrong, because the stator windings are drawn in the wrong orientation

Absolutely, we covered high leg delta in our previous video here ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-u0SsejDCVkU.html

Absolutely, we also cover high leg delta in detail innour last video here ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-u0SsejDCVkU.html

my rental apartment is 120/208v 2x60a

Good example of cooking /heating time differences. To this you could add brightness of lamps. A lamp taken from a 240V supply country would glow only half as brightly in a 120V country.