How does an Induction Motor work ?

How does an Induction Motor work ?


The invention of Induction Motors permanently altered the course of human civilization This hundred-Year-old motor invented by the great scientist Nikola Tesla is the most common motor type even today In fact about 50% of global electric power consumption is due to induction motors Let’s get into the workings of induction motors or more specifically into Nikola Tesla’s genius thinking The induction Motor has two main parts the stator and rotor The stator is basically a three coil winding and three-phase AC power input is given to it The winding passes through the slots of the stator which are made by stacking thin highly permeable steel laminations Inside a steel or cast iron frame When a three-phase current passes through this winding something very interesting happens It produces a rotating magnetic field This RMF is what causes the rotor to turn To understand how the rotating magnetic field is generated as well as its properties let’s consider a simplified stator winding Here the three coils are connected 120º apart A wire carrying current produces a magnetic field around it When a three-phase power is applied to this special arrangement the magnetic field produced will be as shown at a particular instant With variations in AC current the magnetic field takes different orientations If you compare these three instances you can see that it is like a magnetic field of uniform strength rotating The rotational speed of the magnetic field is known as the synchronous speed Assume that you are putting a closed conductor inside it According to Faraday’s law because the Magnetic field is varying an EMF will be induced in the loop The EMF will produce a current in the loop thus, the situation has become like a current carrying loop situated in the magnetic field according to the Lorentz Force law an electromagnetic force will be produced on the loop and the loop will start to rotate The same phenomenon occurs inside an induction motor as well Here instead of a simple loop something very similar to a squirrel cage is used The three-phase AC current passing through the stator produces a rotating magnetic field So as in the previous case current will be induced in the bars of the squirrel cage Which is shorted by end rings, so the rotor will start to rotate That’s why the motor is called an induction motor Electricity is induced on the rotor with help of electromagnetic induction rather than direct connection To aid such electromagnetic induction insulated iron core lamina are packed inside the rotor Such small sizes of iron make sure the Eddy current losses are minimum You can see that the induction motor has a big advantage. It is inherently self-starting As you can see both the magnetic field and rotor are rotating But at what speed will the rotor rotate? To obtain the answer to this question let’s consider different cases Consider a case where the rotor speed is the same as that of the magnetic field Due to the fact that both are rotating at the same speed The magnetic field will never cut the loop Thus there will not be any induced EMF and current This translates to zero force on the rotor bar and the rotor will gradually slow down As it slows down the magnetic field will cut the rotor loop So the induced current and force will rise again The rotor will then speed up In short the rotor will never be able to catch up to the speed of the magnetic field It rotates at a specific speed which is slightly less than the synchronous speed The difference between the synchronous and rotor speeds is known as slip Now let’s understand why induction motors rule both the industrial and domestic worlds You can note that induction motors do not require a permanent magnet They do not even have brushes commutator rings or position sensor like other electrical machine counterparts Induction motors are also self started The most important advantage is that induction motor speed can be controlled easily by controlling the input power frequency To understand it properly let’s once again consider the simple coil arrangement We learned that a rotating magnetic field is produced due to the three-phase input power It is quite clear that the speed of the RMF is proportional to the frequency of the input power Because the rotor always tries to catch up with the RMF the rotor speed is also proportional to frequency of the AC power Thus by using a variable frequency drive one can control the speed of the induction motor very easily This property of the induction motor makes them an attractive choice for elevators, cranes even in electric cars Due to the high-speed band of induction motors electric cars are capable to run with a single speed transmission another interesting property of the induction motor is that when the rotor is moved by a prime mover it can also act like a generator In this case you have to make sure that the RMF speed is always less than the rotor speed We believe that you have now developed a clear understanding of the ingenious operation principles behind an induction motor as well as why it is still ruling the domestic and industrial worlds We hope you will support us at patreon.com So that we can continue our educational service Thank you!

100 thoughts on “How does an Induction Motor work ?

  1. A superb explanation with excellent graphics. You really cracked it here! I've worked with these machines for 20 years and always struggled to explain them to trainees. Thank you.

  2. You cant use an induction motor to generate electric current because there is no permenant magnetic field. You need some kind of excitarion current to induce a magnetic field in the rotor for the moving rotor to produce current in the stator windings. And induction motors are also know as asynchronous motor because it is not synchronous because the rotor speed is less than the rotational magntic field. A synchronous motor which is used in electric vehicels has no slip because the motor speed is the sme ws the frequency or rotation of the magnetin field because it has a permanent magnet inside.

  3. Crazy why Eddy currents matter here but plane propeller wings they don't . So you can use radiator to make power very clear WTF why all do learned . Is like it dumbed all down why Americans all fighting to see who kills America best ifiits learn what this country founded in . Tesla was shown much . Why he wanted to give it away . If he was a Idiot like Westinghouse or illumanti he could of bought and sold all illumanti and Rockefeller rothchild all of the idiots and he died Broke big deal richest guy on plant he was he new it why he stayed just and honest .

  4. 1- speed of the moter can not be more then 100 or 120 cycle per second because it is the frequency of ac current???
    2- direction of the rotation of motor will be decided on what fact??

  5. What if they had a DC motor with a rotor with sections of stator that curve towards the rotor, so that the stator attracts multiple rotor magnets, but then the current cuts off and the cycle starts again?

  6. wow, I learned all of these laws in school, but I never could have put it all together to create or understand this motor

  7. Now make a levitating UFO the germans did it, so can you!! If you figure it out font sell it to the military just drop the video how you did it on everyone's door step

  8. You keep calling it a three-phase motor but almost all domestic properties only have a single phase feed so how come?

  9. Nikola Tesla was a genius. He gave us some much to our modern world. I still don't understand why school textbooks don't tell students about him.😢

  10. Я понял только спмд, кондуктор, сейм и лупа – короче у какого-то кондуктора из сейма под лупу обнаружили спид! А этот кондуктор наверное стырил этот мотор и разобрал!

  11. Пожалуйста, поддержите нас на https://www.patreon.com/LearnEngineering, чтобы мы могли добавить еще одного участника в команду и выпустить 2 учебных видео / месяц.У вас заголовок на русском и просьба на русском. Видео на английском. Вы какую аудиторию просите поддержать вас?

  12. If it’s self-starting and does this continuous slowing down and then speeding up, isn’t this a perpetual motion machine?

  13. How does an induction motor starts!

    :burrrrrm…burrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrmmmmmmmmmmmmm
    burrrrrrrrrrrrrrrrrrrrrr…burrrr…burr…burrrrrrrrrrrrrrrrrrrrrrrmmm….bumm..bumm bu-bumm bumm

  14. For Ukrainian: "Та що ви верзете усілякі нісенітниці! Облиште, геть усе спаплюжили перекладом"!

  15. 22 years since i started as an apprentice winder and induction motor mechanic, this was nice to see, good job and very well explained. 👌

  16. Brilliant… You are ruling the youtube 😛… None of video available on youtube is comparable to it.
    And glad to know that every animation is made in Blender ❤️

  17. Its a very helpfull video as well as very much technical content on it.
    Thank you sir for such kind of representation.

  18. Would it be possible to use laminated, nickel-plated steel disks instead of iron core lamina ( 3:15 ) inside the rotor to minimize the eddy current losses?
    Basically my question is: Would laminated steel disks work instead of iron disks?

  19. still after 30 years of my education find it hard to understand ac electromagnetic units, will watch again & again to understand it.

  20. Interesting so there is no need for coil excitation as well? Even when used as a generator? Also why are the squirrel cage bars at an angle, I'm assuming there is a reason?

  21. So when you supply dc current to each of the three winding at the same time you get a rotating field in the way you are showing? And the coils don't seem to be wound like spring but just like looped twisted wires, basically like a cable that is made with stranded wires. And each winding look identical. Oh, you got more clear in the second part. AC current.

  22. Thanks a lot for the vdo. Respect every scientist or physicists bcz they gave all several contribution in several fields.

  23. Does this mean that the induction motor rotor is limited with the max speed by the frequency? 50 to 60 Hertz? I know you can get variable frequency drives to control the frequency within the 50 to 60 Hertz.

  24. I just had a chapter on induction motors for my HVAC class. This helped me cement my understanding of an induction motor. Thanks for the video!

  25. It would be great f you could upload a simple video showing the magnetic field around the coil using the angle of 2:13 (this animation is too short, and start with a weird/confusing angle, after 2:13 it's easier to see, but it's too short). You already have made the hard work with your 3D software, you just need to publish a 1 minutes of it. Com'on!

  26. 2:56 "which is shorted by end rings, so the rotor will start to rotate" (I guess it means that the bars of the squirrel cage touch each others on the front and back), but
    1) where the electricity produce by induction goes on the bars? (There is no ground right?).
    2) What would happens they were not shorted?
    3) And what would happen if the bar where not laminated but made of a single copper piece.

  27. @2:57. Is are the arrows on the square cage showing the induced flow of conventional current or electron flow?

  28. Except that Tesla 3 is switching from induction motors (as in model S) to permanent magnet (e.g. neodymium) motors (they say "to improve efficiency").
    Otherwise great graphics and amazingly well presented.

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