What is the Difference Between Single Phase and Three Phase???

Single phase power and 3 phase power are terms we hear quite frequently in the electrical world. But what are the differences between them? In the latest episode of Electrician U, Dustin explains the differences and benefits to each in a never-ending pursuit to answer our followers’ questions.

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Let’s start off by defining them. Single phase is referring to a single loop of current flow. One big loop! One can also think of single phase as two hots (typically A and B phase or Black and Red). Current is flowing TO the load on one wire (say the black wire) and returning TO the source on the other wire (say the red wire). They are also alternating back and forth between pulling and pushing the current flow. Try to conceptualize the sine wave chart. As one of the conductors is pushing the current (black), the other is pulling (red). Until they both get to the neutral (or zero point) where it begins to go the other way. Black will pull and red will push.
Three-phase on the other hand is referring to 3 loops of current flow from 3 separate generating sources. Same type of general concept except that they are tied together. As before with single phase, current left on the black, travelled thru the load, and returned on the red. Here in three phase, current leaves on the black, travels thru the load, and returns on the red. However, that red ALSO happens to be powering the one side of its own generator as well that will leave on its red conductor and return on another conductor (blue). This blue is ALSO tied to ITS own generator that current will leave on the blue, travel thru the load, and return on the black, and we start the sequence all over again! So, they are all separate loops but tied together to form another loop so they can share the load amongst themselves.
The terms Primary and Secondary also come into play here. Primary refers to the conductors on the side Feeding the transformer, Secondary refers to the conductors on the other side that will be utilized by us. Transformers operate by induction. When we push/pull current thru the transformer on the primary side of the coil, it induces movement of current on the other secondary coil (transformers have coils that are close to one another but not touching) and that current flow is what provides us the stepped down power we need.
One of the big reasons WHY we would use 3-phase for some applications is due to efficiency. Remember our sine wave chart? On single phase, work is being done when the points are at their farthest distances apart from one another. But when they both come back to the zero point (at the same time, remember), there is no work being done at all as they are both at zero. On a 3-phase system, when one of the 3 phases is doing ALL the pushing, the pulling action on the other end is being shared equally by the other 2 phases. And that alternates between all three of the sets. So, on a sine wave chart, when one conductor is at its highest point, the other two are not exactly opposite of it because they are sharing the work. And, then THEY alternate also. So, at no point is anything sitting idle on a three phase, thus more efficient for larger scale type items like factories, plants, warehouses, etc.
We can also get motors in either single phase or three-phase. Same type of concept and for the same reasons. Efficiency! The three-phase motors share the work among the three points of power.
We hope this answers the age old question of the differences between single phase and three phase. Please continue to follow Dustin and Electrician U as we are constantly adding new content to bring clarity to the electrical trade!

#electrician #electrical #electricity #

[vinzo]

The clarity by which something is defined will determine the effectiveness of its application. Nice work!

[BLud_Bro_FoE]

I am a field electrician and I was unable to go to school, I'm so appreciative of all the content you put forth .thank you so much

[anobody]

The reason why he can explain things this well is because he really understands what he's teaching. If you can't explain something complicated in simple terms then you really don't understand it. These are in some ways not advanced concepts but the way he explains it makes it 100 times easier to understand. Great work.

[Leomej]

I’m a 1st year and always have trouble understanding this. I just knew three phase had 3 hot conductors and single had 2. You’re a great teacher man, seriously thank you

[mollymikna]

Very well done, Dustin. I am a Professional Engineer in Electrical Engineering and you explained a tough concept/topic very well, indeed! Thank you!

[ronlovell]

Excellent simplified explanation, including capacitors at the end. Thanks Dustin!

[retiredfedleo]

Pretty obtuse subject for the average person, very well explained. You have a knack for teaching. Kudos!

[frankgonzalez]

Open up a car alternator. If you look closely at the stator setup in the alternator, you will see it is made up of three separate windings/stators. The three windings/stators produces three phase current as they are set at 120° apart from each other. What turns the three phase current from AC to DC is the diode trio the stators are connected to. Car's used to use generators. The reason alternators are used instead of generators is because alternators are more efficient, smaller and can be controlled easier than generators.

[georgesimpson]

I just completed a four year degree in Electrical engineering, but it is this 23mins video that has given me the understanding... 👍💯

[alexdasilva]

This is an incredibly difficult topic to explain to a DIYer or someone new in the electrical field, yet you cover it expertly and clearly. Thank you so much for everything you do to help us along!

[claimjumper]

I stand amazed. I actually believed I’d never be able to grasp this whole thing, but now I get it. What an excellent presentation. Thank you.

[TeslaFan]

That was fantastic! It’s the first time I truly started to understand some of the principles of electricity! You did a marvelous job in presenting it simply.

[erich]

Could you imagine if Dustin had to keep his hands in one spot for one video? He would probably internally combust lol

[vel]

Good video Dustin. This also happens in reverse even when we don't want it to with three phase. I work on a lot of pump Jacks for oilfield and when they are on drives and the weights are out of balance and crest over the peak and they are weight heavy they start pushing the motor and the motor starts generating voltage back into the drive. This has to either be fixed by balancing the weights properly or a dynamic breaking resistor put in place to catch the motor generated voltage and it shunts it and turns it into heat

[vids]

I think what confuses many new electricians is that we deliver single phase power (to residences) but most of the circuits we use are split-phase. Graphing an example of split phase is helpful. It also helps them understand crossed phases.

[jonathanhaynes]

I'm approaching 60 and I never understood this as I now do. Your breakdown was the key--simple but detailed at the same time. Cheers.

[naturesrelaxationmedia]

Oh, one last comment... maybe 25 years ago i was obliquely involved with the sale of a huge printing company... they moved their ginormous Heidelburg Press to a location that was cost prohibitive to bring in 3phase.... i was fascinated by the way they resolved this... and intently watched out of curiosity this entire process and could understand the electrical hook up but your video shed new light on it... causing a full understand of what they were doing... anyway they made and hooked up a single phase to 3 phase motor device that used single phase to generate onsite 3phase... your explanation in this video sparked that memory and a 25yr old Light Bulb Went OFF.... freak'n cool... the new owner of this company was a very smart guy and smart people rule... : ) you sir obviously like what you do and are a very good teacher to boot, good for you and continued much sucess... " GOAT " status for sure.... hahaha 👍

[bladejacobs]

1st month completed as an apprentice, was told to rephase Motors and when the boss explained i was lost. This visual helped me a lot when I had my lunch break! Thank you

[jimmysmith]

awesome video thanks. im a engineer on a tug boat and we use 3 phase on our gens. i been to some schools for electronics but it was never explained like this. i appreciate it i have a better understanding of how it works now.

[Tom-ftsb]

Best explanation i ve ever heard for this. I'm 60 years old and have been trying to understand this my entire life. great job