What is an INDUCTION MOTOR (THREE-PHASE ASYNCHRONOUS MOTOR) - RMF Rotating Magnetic Field
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- เผยแพร่เมื่อ 9 มิ.ย. 2019
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An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding.
Since 1885 Italian inventor Galileo Ferraris had shown that two orthogonal coils, in which alternating currents out of phase by 120 degrees flow, generate a rotating magnetic field.
After years of study, Ferraris was able to publish the results of his experiments in 1888.
But it was already in the autumn of 1887, that Serbian physicist Nikola Tesla, after mastering his engineering work on the induction motor, yelds the first patent application.
Today, almost the 90% of industrial engines is represented by induction motors.
Induction motors can be considered among the most reliable electric machines since they keep unaltered their perfomances for many years, with very low maintenance operations.
Let’s try to see in detail the inner working principle of these engines.
The induction motor consists of two main elements: the stator, and the rotor:
The stator is basically a three-coil winding powered by three-phase alternating current.
Each winding passes through the slots of the stator, which are made by stacking thin layers of steel with high magnetic permeability inside a steel or cast iron structure.
The flow of a three-phase current through these windings causes the formation of what Galileo Ferraris had already discovered in 1885, namely, a rotating magnetic field.
It is precisely this rotating magnetic field, R-M-F, that causes the rotation of the rotor.
To better understand how the rotating magnetic field as well as its properties are generated, let us take as an example a simplified version of a stator winding.
As we can see, this winding consists of three coils, connected 120 degrees apart.
A current-carrying wire, generates a magnetic field around it.
If we apply a three-phase electric power to this coil arrangement, the magnetic field will be generated at a specific moment, as shown.
Following the variations of the alternating current as shown, the magnetic field will assume different orientations and form.
When we compare these three results, we can see that it is like the rotation sequences of a magnetic field of uniform strenght.
We can call "synchronous speed" the rotational speed of the magnetic field.
Let’s try now to place a closed conductor inside the rotating magnetic field.
Since there is a variable electromagnetic field in a closed circuit, an induced current will be created on the conductor. We can therefore say that the rotating magnetic field will induce a current in the loop.
So, the situation obtained is a loop subject to induced current, located in the magnetic field.
Like we’ve already seen in our last experiment, the Lorentz force was responsible for the rotation of the tin wire placed over a battery and a magnet. The wire was immersed in a magnetic field and while the electricity flowed into it, a perpendicular force acted on it letting the rotation happen.
Also in this case an electromagnetic force will be produced on the loop, allowing the rotation of the connected rotor.
This same phenomenon happens inside the induction motor, with the only difference that the loop is replaced by a squirrel cage rotor.
Also in this case, the three-phase alternating current, passing through the stator produces a rotating magnetic field.
This is why this engine is called an "induction motor".
Electricity is induced on the rotor by electromagnetic induction, and NOT by direct electrical connection.
To facilitate this electromagnetic induction phenomenon, layers of iron sheets are enclosed within the rotor.
These thin ferromagnetic material layers favour the magnetic induction and minimize the eddy currents.
We can deduce that the induction motor is, by nature, self-starting. This means that: by varying its speed, It spontaneously and automatically develops a driving torque, able to counterbalance the resistant torque applied to the motor shaft, determining a stable operation.
As we can see in this animation, the magnetic field and the rotor are rotating, but how do we know the exact rotational speed of the rotor?
First of all, let’s suppose that the rotor is rotating at the same speed as that of the electromagnetic field.
The same rotational speed of both allows the magnetic field to never cross the loop, so the Lorentz force will be zero... - วิทยาศาสตร์และเทคโนโลยี
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Thank you so much, I used this information for my homework. I'm studying electrical engineering in Mexico at the best school of engineering on the country.
The 3d animation was very useful!
All of your videos are great!
Thanks for these wonderful sessions.
I am glad that I found this channel!!
High quality video!
Nice and clear explanation
I love the way you explained this topic was very educative
Good tutorial for basic know how.
Perfect. Video
Amazing, very useful video
Well done! #inductionmotor
Very interesting video
Please visit our website www.jaescompany.com to see our new projects and find out who we are.
Excuse me
Can induction motor used for long time such one year continuously? With load torque of 10 N.m
The video is excellent in many ways. It could have been mentioned that the relation between the coils of the stator and the loops of the rotor are in fact acting as a conventional transformer with a primary and a short circuit secondary. Also, I do not like to say that the induction causes a current to flow as the sequence is in steps where the fluctuating magnetic field from the stator will induce a voltage in the loop of the rotor which could be open circuited and there will be no current only a voltage and so the rotor will not run at all. Due to the short circuit of the squirrel cage effect on the rotor, the induced voltage will create a current in the rotor loops which in return will create a magnetic field in the rotor which will react which the field in the stator which caused it all to happen. It is imperative to understand that voltage is induced in the rotor if the copper in the rotors has a RATE OF CHANGE WITH RESPECT TO THE ROTATING FIELD. and so for this to happen the rotor must never rotate at the same speed as the rotating field on the stator. It is like a person running with the wind if he runs as fast as the wind in the same direction he will not feel the wind in his face nor on his back, but if he runs faster or slower than the wind then he would feel the wind, IN the case of the induction motor, the rotor loops run at a slower speed than the rotating magnetic wind!
During the video, at all times the rotor loop was shown it is always shown running at the same speed as the magnetic field and also the orientation is such that there will be no voltage induced it as the electric loop is not curling the magnetic loop and as sown there is no rate of change of the magnetic field with respect to the loop, hence no induced voltage nor current in the loop.
At 7:15 the rotor loop should have a rate of change with respect to the stator rotating field.
I would say that it is important to show that Curl H= J + dE/dt but in this case, forget about the latter. hence Curl H=J wherein the case of an induction motor both H and J must have a rate of change as it will not work with DC.
Perhaps a mention of the stepper motor or the DC brushless motor could have been mentioned but then the induction due to the rate of change of the stator magnetic field with respect to the rotor loops would not have been indicated only the rotating functions due to synchronous rotating field as in the synchronous motor when the rotor of an induction motor carries a permanent magnet or a DC field so that it will lock on to the rotating stator field.
Dear Carmel thank a lot for your time and for advice and correct us.We create a new video about plane can you leave a comment and tell us what do you think new version th-cam.com/video/OCh4svEfDmE/w-d-xo.html thanks
Ohw lovely good for all stage people,good luck dear sir
Dear Jerald thanks I advise to watch this video too about motor
th-cam.com/video/VaWGJVHiJC8/w-d-xo.html
OK- You say Lorentz force is what's causing the rotor to turn. What I can't grasp is if Lorentz force is causing the rotation then that rotational force from the Lorentz effect would be applied to the rotor at the moment of start-up when the rotor is stationary. If that's the case then why does a single phase AC induction motor require a starting winding or a shaded pole? Seems like the initial rotor rotation from standstill would take place solely from Lorentz force therefore not requiring the starting winding. Try and clear this up for me.
strong graphics for comprehension
What is an pole in a Induction Motor
very nice explanation
Thank you so much!! If you're interested you can also watch our video about the working principle of DC motors: th-cam.com/video/XiGBl-iIYXc/w-d-xo.html
So that's how induction motor starts!
You can also watch our video about the working principle of mobile phones: th-cam.com/video/3xKn99QMudY/w-d-xo.html
wow loved it kindly also make video on three phase transformer
Hello! Thank you for your comment! We made a video about the workin principle of transformers. If you're interested you can watch it and tell us what do you think: th-cam.com/video/fbu1Xji27vc/w-d-xo.html
@@JAEScompany thanks for replying
You were correct in that I found this video highly informative and your narrator does an excellent job of making each point. These lessons are enjoyable to say the least~!! Many thanks for your work on these videos.
We would like to thank you for your kind words! We are glad that our videos are watched by competent people like you! For this reason we'd like to know your opinion about this video we made, in which we explain the working principle of another type of electric motor: the INDUCTION MOTOR th-cam.com/video/EcbHEOIVGcg/w-d-xo.html If you want to learn more about our projects, please visit our website www.jaescompany.com/
very helpfull
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Good info
thank you Issa where are you from ?
Tesla cars use battery packs so inverter is required. Can your inductance motor be use without the inverter if my car does not use battery pack?
No. Alternating current is important in it's rotation.
Nikola Tesla (1956-1943) - 0:54
1856-1943
very interesting, however some induction motors do use a permanent magnet rotor.
Hello. Thank you so much for your observation! We welcome anyone who brings its own contribution and share its knowledge on our videos. This allows us to improve our contents as well as to correct any misunderstandings. So, if you're interested you can also watch our video about the working principle of a very important device in electronics: the DIODE th-cam.com/video/vqQQN5yf1Oc/w-d-xo.html You can also visit our web site to find out our next projects www.jaescompany.com/
@Grumpy
If it has PM magnets then it is NOT an induction motor. The **KEY** word is INDUCTION. With PM magnets there is no need for induction so it becomes a brushless DC motor or a synchronous motor when it uses PM magnets. Please learn your terms...
Hard to ignore Nikola Tesla 1956 - 1943
mistake 😁
That is a relatively fair assessment of an induction motor. Instead of using a permanent magnet in a rotating electromagnetic field, the em field creates or induces a magnetic field in the rotor.
If we look at Teslas original patent he used a permanent magnet instead of a squirrel cage which differentiates his design from an induction motor.
The clever thing about Teslas was that it was a universal motor and could be driven with AC or rotating DC, which is simulated alternating current used in "brushless DC motors". 😉
thanks you for your comment
4:24
Tesla - 1856-1943
Hello Karl. Unfortunately we made a typing error. Thank you for the correction! Have you had the chance to watch our video about transformers? th-cam.com/video/fbu1Xji27vc/w-d-xo.html We would like to know your opinion about it. If you want to learn more about our projects, please visit our website www.jaescompany.com/
The
00:51 Nicola Tesla 1956 - 1943?
thanks you I think is a mistake thank to notice
subscribed! thank you so much for your work. just reading this material is horrible
now somebody tell me why not all cars are powered by electric motors they are so simple and basically no maintenance i mean it would be in the intrest of the owner to pay almost nothing for maintenance and for powering it.. 85% efficency vs 30% in a combustion engine says everything
Yes exactly. They have had the technology for electric vehicles more than a century but only recently is it finally catching up
@@larslover6559 Battery technology is the hold up.
The fundamental problem lies in the production and disposal of batteries, the battery charging times, and, most importantly, in generating sufficient electrical energy so that all cars can be powered by electricity.
We recommend watching our video on thermal power plants: th-cam.com/video/Ht2wgH_EWQU/w-d-xo.html
Regarding electric cars: th-cam.com/video/flQSQxHVS14/w-d-xo.html
Who is studying for PE exam here 😅
Nice and clear explanation