# How does a Transformer work – Working Principle electrical engineering

Hey there guys, Paul here from TheEngineeringMindset.com. In this video, we’re going to be looking
at how transformers work. Now this follows on from our series on electrical engineering, so do check out the other videos if you’ve not done so already. Links are in the video description below. Coming up, we’ll be looking at how
to create a magnetic field with electricity, and why only an alternating
current can be used in transformers. How a basic transformer works, then we’ll look at step up
and step down transformers, and finally, we’ll finish on three phase transformers. Now there are two types of electricity, AC and DC. But transformers can only work using AC, or Alternating Current. And if you don’t know the
difference between these two, then please, first of all, watch the video on electricity basics first. Again, you can find links to these videos, and other useful videos, in the video description below. When we connect an AC generator to a closed loop of cable, a current will able to
flow through this cable, and the direction of the
current will alternate backwards and forwards, with the rotation of the generator. The alternation means that the
current reaches it’s maximum and minimum point during the cycle, which gives it its sine wave pattern when connected to an oscilloscope. Now you can think of this
as the tide of the sea as it changes direction, and reaches its maximum and minimum point. As the current flows through the cable, it will emit a magnetic field. If we pass DC current through the cable, the magnetic field will remain constant. But, if we pass AC
current through the cable, then the magnetic field will increase and decrease in strength, and changes polarity as the current changes direction. If we place multiple cables together and pass current through them, then the magnetic fields will combine to create a stronger magnetic field. If we then wrap the cable into a coil, the magnetic field will
become even stronger. If we then place a second
coil in close proximity to the first coil, and then we pass AC, alternating current, through the the first coil, then the magnetic field it creates will induce a current
into the second coil. And this magnetic force will push and pull on the free electrons
forcing them to move. The key component here is
that the magnetic field is changing polarity as well as intensity. This change in intensity and direction of the magnetic field constantly disturbs the free
electrons in a secondary coil, and this forces them to move. This movement is known as
electromotive force or EMF. Electromotive force does not occur when we pass DC current
through the primary coil, and that’s because the
magnetic field is constant, so the electrons are not
being forced to move. The only time it will
cause EMF is very briefly when the primary circuit
is open and closed or when the voltage is
increased or decreased. And that’s because these
actions result in a change to the magnetic field. Therefore, we use alternating current as this change occurs constantly. Now, the problem with this setup is that a lot of the magnetic
field from the primary side is being wasted because it’s not in range
of the secondary coil. So, to fix this engineers place a core of ferromagnetic material such as iron, in a loop between the primary and secondary coils. Now, this loop guides the
magnetic field along a path to the secondary coil, so that they will share the magnetic field and this makes the transformer
much more efficient. Now, the use of an iron core
is not a perfect solution, some energy will be lost through something known as Eddy currents, where the current swells around the core and this heats up the transformer, and this means that the
energy is lost as heat. To reduce this engineers
use laminated sheets of iron to form the core, and this greatly reduces
the Eddy currents. Transformers are
manufactured to be step up or step down transformers, and these are used to increase or decrease the voltage simply by using a
different number of turns within the coil on a secondary side. In a step up transformer the voltage is increased
in the secondary coil, and this will mean that
the current will decrease. But don’t worry too much right now about why that occurs. We’ll look at this in a later
electrical engineering video. To increase the voltage
in a step up transformer, we just need to add more turns to the coil on the secondary side than the primary side. In a step down transformer, the voltage is decreased
in the secondary coil which means that the current increases. To do this we just use
less turns in the coil on the secondary side
compared to the primary side. For example, a power station needs to
transport the electricity it is generated, over to a city some distance away. The power station will
use a step up transformer to increase the voltage and reduce the current, as this will reduce the losses for the long transmission cables. Then, once it reaches a city, this will need to be reduced to make it safe and usable by buildings and homes, so there will need to be
a step down transformer. The Transformers for commercial buildings and power stations are usually in a three
phase configuration. You’ll see this placed
around your cities and towns, and they’ll look something like this. These three phase transformers
can be made from either three separate transformers
that are wired together, or they can be built into one large unit with a shared iron core. In this set up, the coils will typically
sit concentrically within one another with a higher voltage coil on the outside and the lower voltage coil
sitting on the inside. Now these coils are
insulated from one another, so that only the magnetic field will pass between the two coils. To connect the two sides there are many different configurations, but one of the most commonly used, is to connect the coils in a configuration known as Delta Wye, sometimes referred to as delta star. This refers to the
primary side being wired in the Delta configuration and the secondary side being wired in a wire configuration. The centre point of the wye side where all three connectors meet, is often grounded which allows for neutral
line to also be connected. we’ll cover transformer connections and calculations in other
more advanced videos as this can get quite complex, so for now, simply focus on how they work to build your base knowledge. Okay, that’s it for this video. Thank you very much for watching. I hope you’ve enjoyed this and it has helped you. If so then please don’t

## 100 thoughts on “How does a Transformer work – Working Principle electrical engineering”

1. The Engineering Mindset says:

⚠️ Found this video super useful? Buy Paul a coffee to say thanks: ☕

PayPal: https://www.paypal.me/TheEngineerinMindset

2. Frozen Toys says:

Correct me if i'm wrong, the current produved in the secondary coil has an induced emf from the first coil that has alternating magnetic field from alternating current. Which means the magnetic field reverses and so would the secondary coil be AC again?
How does the secondary coild become a DC. Can someone explain?

3. Dunbar Tuason says:

I assume it possible to step up 240 1ph to 480 3ph…..however if you have a 1ph 120/120 line IN, whats the safest way to introduce the L3 from either L1 & L2 on the Step transformer so it powers a 3ph 480 motor without the use of an idler motor phase converter ? Thank you

hui

5. carl browning says:

Please do a basic video on contactors.

6. Ubong Libat says:

Ohhh so that's the growth of the magnetic flux. Thanks (your animation helps me understand)

7. Alain Hardy France says:

J'adore ta vidéo, Bravo pour ta chaîne !

8. Riley Archer says:

I am confused as to why increasing the voltage reduces the current. I can see from the equation P=IV that for a given P you can increase voltage and it decreases current but when you look at the equation I=V/R is says that when you increase voltage then current also increases for a given resistance. Can you please help me understand better?

9. Silvio Roesler says:

Thanks for posting, very informative

10. Andrew Thacker says:

Good info

11. JCM Fitness says:

I’m a first year apprentice so it’s nice to learn these things

12. Alain Hardy France says:

J'adore ta vidéo, Bravo pour ta chaîne !

13. Justin Justin says:

This videos might help me thru school ??

14. Why So Serious? says:

All I know is that..

There more than meets the eye..

They even could be..

Robots in disguise

15. hernje says:

Can you please explain ferro resonance?

16. ayman antoun says:

Thank you very much
I greatly appreciate your video and enjoyed watching it couple times
how the synchronous motor works and induction motor works also?
Look forward to hearing from you
Thanks again for the great work

Myles?

18. VIKDR says:

Still don't know how a truck turns into a giant robot.
(Sorry, couldn't help myself.)

19. Birney Ombok says:

Am an undergraduate student interested in electronics so much,how I wished I could find your books if there is any

20. Paulo Ricardo says:

Thank You so much! ( I am Brazilian)

Nice

22. HO LEE FOOK says:

So what if you used gold wire in place of the copper wire in a generator….has this ever been done

Excellent vid – thanks. However. it appears 2 me that U r depicting maximum field strength at 90° from the poles

24. Justin Justin says:

Failing my dc circuits class wish I had ur knowledge I had the fact I’m failing so disappointed…..7 days left in class no coming back

25. Chris Cash Music says:

Optimus Prime approves this video!

26. TheRobb573 says:

I work as a wireman for Central Electric, and they don't even begin to cover how electricity itself work, much less 3 phase and transformers. They teach you how to crimp terminals onto wires. Most of us never gets to see or know what this equipment does, but essentially we wire up giant breaker buildings and stuff for power substations and companies.

27. Mr Tech Trip says:

Nice video, very informative

28. Bikerchris says:

Wow, great video. Only down side is I now feel like an chimpanzee compared the the people that invented and engineered this so many years ago.

29. Jeremie Russie says:

please you can make some theory video for electrical for exams

30. David Tan says:

Thank you Paul?

31. Neal Cromwell says:

Red yellow blue 20 years out of date there i rembember ryb but the youngsters will not have a clue and you must be one of them

32. bigpardner says:

For instance the circuits at 2:05. If a switch is on the secondary side turning off the light bulb, the primary side is still open and using energy? Is a transformer using AC from a power source constantly using the same power regardless of what is being used on the secondary side?

33. Josh K says:

In 6 minutes and 30 seconds you have just explained a weeks worth of classroom book study.

34. David 3D says:

Thank you so much

35. gearstil says:

At the min 1.07 the maximum voltage should be when the magnet is in line with the coils, not perpendicular.

36. Xeno Bardock says:

I think the power companies also use the oil cooled capacitors for high amps if i am correct.

37. Rambo's Clone says:

What happens to current when voltage steps up? I've heard the current drops but ohms law says the current should also increase unless the resistance also increases.

38. lazy gizmo says:

If AC goes back and forth, how does AC get pushed through power lines into buildings from the power plant?

39. xierxu says:

Delta/meshi or Star/wye

40. Tomis Kroondyk says:

41. Xeno Bardock says:

Transformers are like a tank. If you step-up voltage, its like filling a tank so current decreases while voltage increases. If you step-down voltage, its like opening a faucet so current increases while voltage decreases.

42. Joel Snyder says:

I am an electrician. Thank you for helping increase my knowledge on how the things we install actually work. Great job, keep the videos coming

43. The Engineering Mindset says:

⚠️ Learn how INDUCTION MOTOR works here: https://youtu.be/N7TZ4gm3aUg ⚠️

44. physics quantum says:

you're the best!! There are no comments on the best video.

45. кто-то что-то says:

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хохо юморок мой юморок эх какой я сасный

46. Krizhnan Kanna says:

you made my day sir,greatly thankful to you,got clarified all my doubts……

47. Ice Rink Diaries says:

Great video. We have transformers around the ice rink and always wondered how they worked. One step closer.

48. NorthernCaliWay says:

Thinking of being an electrician this is a great reference for basic electrical theory

49. IQ NET says:

The only guy who makes internet more meaningful. Thank you sir!

50. PVG Automation says:

Very good video

51. Richard Vaughn says:

One correction though, in north america we use Y to Y transformers for almost all 3 phase service. Distribution grids are typically Y connected but transmission grids are delta connected. 3 phase service is usually just 3 single phase transformers matched and installed beside each other.Rarely you will find 3 core 3 phase distribution transformers used by some utility companiesand sometimes the single phase transformers may be connected phase-to-phase/delta probably depending on the specs of the available supply of transformers on that particular day of installation.

52. bluewaters4567 says:

What do you mean when you say that power stations will use step up transformers to increase the voltage but reduce current to minimize losses over long distances. Does not increasing voltage, increase the current? Is some form of resistor involved to reduce the current?

53. Grey the Wolf says:

Great, this video really helped!

… now, back to opening up that transformer…

54. LORD PRETTYBOY says:

great vid! Hours of trying done in 5 minutes

55. anto Urvez says:

Awesome work Paul and buddies

56. aldo ratmawan says:

Thanks you

57. van lal zual pc. says:

Ulternating current!

58. Sailus54 says:

You really nailed it with those animations. One thing i noticed is there is nothing showing that the current and flux get's larger and smaller during the constant changes, but that may over complicate things. It took me a lot of effort to figure out what alternating current and flux was and I think a lot had to do with lack of good visualization and explanations. Great video

59. Eric Fisher says:

But why the current pass through the coil and not just short-circuit across it?

60. Heather Schulz- Behrend says:

Here is the secret to the transformer nice.

61. Rami A.A says:

Thoroughly enjoyed it thank you

62. Kim Jong Trump says:

Great content ??

63. Timothy Mckee says:

But's that's not what Optimus Prime taught me!

64. Music Unlimited says:

Please make a video on star ,Delta connection

65. ALG hocine says:

thank you

66. Walt Kuznicke says:

Thank you so much ,,,,, from your pleasant audible speech tone, and your very clear and minimal accurate word descriptions. As an electrical engineer I have been the victim of every confusing, inept, stupid, and misleading electrical basics theory in text book form and classrooms. Which proves there's many degreed ill informed idiot authors and their multiplying, the material is simple and understandable if presented in a well informed unassuming way, my sincerest gratitude. It is not magic, but requires an adult SENSITIVITY maturity in educating science .

67. zk zk says:

Tesla

68. Brandon D says:

They mentioned that with the use of Transformers, increasing the voltage decreases the current. They said they would talk more about this later but I cannot find any video where they do. Based on everything I've learned so far about electricity increasing the voltage should increase the current. I've looked all over the internet and found that a lot of people concur with this except on the subject of power lines and Transformers. everyone then says as the voltage increases the current decreases. I have looked all over and cannot find anything that clearly explains how both statements can be true

69. Patrick O'Connor says:

I can seriously appreciate this video channel and the use of animations while the narrative is going on. Something that is often not used in electronic tutorials. GREAT JOB 'The Engineering Mindset' !!! 😀

70. MunsKi says:

the best explanation

71. Highly Polished Turd says:

I've known for decades that transformers have laminated cores, but until now, I didn't know why! I just stumbled across this channel today, and liking it. There's a lot of this I already know, but you are filling in some gaps in my knowledge.

72. beeps says:

Am i the only one who wanted to play Simcity at 3:50?

73. Nim ra says:

In which video does he explain the reason behind current decreasing when voltage increases ?

74. Bett Kiprotich says:

How transformers used in mobile phone chargers operate?

75. rameez shaikh says:

Nice Video ?

76. Sony Rajan says:

Why lv side delta connected?

77. E5Bobby says:

Very well done!  As basic as you've broken it down, and I don't think it can get more basic than what you've done I still need some time for my brain to arrange its thought-process so that this is locked in and not some foreign concept.  The bottom line is that I may watch this several times in order to really know it.  I would rate your video "A+"!!!

78. Md Ashif says:

Why the transformer rating as kva not in Kw?

79. elrunnerdave says:

wow thanks!

80. gaurav proton says:

I needed this thx.
subscribed

81. Brown Uwa says:

The theory of DC current no able to cause magnetic induction was not detailed. You know core carried Magnetomotive Force MMF. the Primary coil and the secondary coil are not electrically coupled together except in the case of Auto-transformer but magnetically coupled together. as you have electrical circuit on both the primary and the secondary where you have the Voltage (EMF), Resistance(impedance) and current which give Voltage (emf) =IxZ, so also you have Magnetic circuit of the CORE where you have magnetomotive force (MMF), reluctance ( R) and Flux linkage MMF=Rx(flux). please can you clarify if DC create Magnetomotive force

82. Matt Maloney says:

Awesome. Thanks.

83. ATIF NACHAN says:

awesome lecture, kindly make a video on diode

84. Benard Asiimwe says:

Hello I have a disturbing question.
I watched a video of students coming from school on a rainy day,
The area was flooded with water and they were trying to cross ,one of the students touched electric pole and power got him ,so the frd tried to help and it got him too,another come to help them but he was stopped by a teacher.Now my question is since water is a good conductor of electricity ,why is it that the other students crossing the same flooded water ,were not affected and even those near them pole , thank u

85. Thomas Sparling says:

Great videos . Please continue to develop more ?

86. mos ab says:

4:05 That's what I was here for. Does anyone know in which video he talked about it?

87. tom110111 says:

What is the difference between a transformer and a rectifier? My understanding from watching your video series is they both convert AC to DC.

88. mark Koliboski says:

Do you know anything about DC cranes and how dynamic braking works?

89. Gerardo Sanchez says:

Why doesn't a generator short? It doesn't have a load, it does have a transformer but those just windings so why does a generator side of generation not short?

90. Hambone says:

Thank you.

91. AJ says:

At 4:40 you mentioned how a power station would use a step-up transformer to increase the voltage… but why would it also decrease the current? Ohms law says the voltage is directly proportional to the current, so I don't understand why increasing the voltage through the transformer would decrease the current.

EDIT: after some googling, I found out that what's missing is the idea of Power which is a product of the voltage and current: "to maintain the same power, if we increase voltage, what happens to the current?". This concept is missing from the textbooks and this video =( Also the voltage in Ohms law relates to potential difference (i.e. between two points) not along a conductor.

92. Jake says:

When is another transformers video coming?

Thank you

94. SKIES TOOK MY DRONE says:

very right thank you.

95. Rolf Müller says:

96. SDK says:

Where's the advanced video on Transformer?

97. mark melnyk says:

Generally speaking the line side of a transformer, primary coil, is the delta, and the load side of the transformer will be a wye connection. So that whatever device you are powering you are able to add a neutral.

98. LOYISO VICTORY says:

my oh my, why didn't I meet you sooner? Could have saved me a lot of headaches.