Understanding STAR-DELTA Starter !

Understanding STAR-DELTA Starter !


Three-Phase induction motors are the workhorse of modern industry due to their robustness and simplicity. You might have seen that in order to start a high power rating induction motor a starting technique called [Star-Delta] is used. In this video we will understand why a star double starter is needed and how it is accomplished practically. To understand why a star delta connection is needed [a] proper [understanding] of induction motor operation is imperative. The induction Motor has two main parts a stator and rotor. The input power is given to the stator When connected to a three-Phase power supply the stator of a three-Phase induction motor produces a rotating magnetic field. The RMF is the one which makes the rotor turn. Let’s simplify this winding to understand the connection This is the simplest coil arrangement to produce an RMF. We have three coil sets as shown let’s Denote it with U V and w The ends of each coil are represented as [one] and [two] respectively When excited by a three-Phase ac power supply this simple coil configuration will produce a two pole rotating Magnetic field. This rotating Magnetic field will induce electricity in the rotor bars according to electromagnetic induction So the ruler is like current carrying bars immersed in a magnetic field This will induce an electromagnetic force according to lorentz Force law and the rotor will rotate in the same direction as the RMS This is how the induction motor works. Electricity is induced on the rotor bars due to electromagnetic induction rather than direct connection So it is clear that the induction motor works due to transformer action The stator coil acts like the primary of a transformer and the rotor bar as the secondary Here comes a really interesting problem think of the rotor RMF interaction at the starting of the motor When the induction motor starts the rotor speed is zero and slowly increases This means the rotating Magnetic field will cut the rotor bars at a very high rate As the rotor Gain speed the rate of Flux cut will decrease So a high Emf and current will be induced on the bars at the start As the rotor speed increases the current will lower to the normal value At the start stator current also must be high since the rotor and stator current are coupled due to transformer action Due to this the stator coils will draw a huge amount of current when the motor starts This will produce a large voltage drop in the line and affect other devices when a heavy rating induction motor starts How does one overcome this problem? Star Delta Connection is one of the most commonly used solutions for this You can see in the current design that all the ends of the coils are free We could connect one free end of each of the coils in two different ways Either as star where the end terminals are together Or as Delta, with the one coil is connected to the start of the next coil. This is clearly depicted in the schematic. When we apply a three-Phase voltage across a star connection each coil will receive a much reduced voltage Whereas if one applies a three-Phase voltage across the Delta configuration we will get the same applied voltage So the trick to overcome the high start and current is simple just connect the coils in star at the starting Reduced input voltage means reduced current at the stator coil To necessitate disconnection all the terminals of the coils are fed to the junction box of the motor they are arranged in the following manner. input power is given to the terminal one of the coils. To connect in star what we have to do is just connect the second terminals together After the rotor reaches a considerable speed, the stator current will be normal so that we can switch to Delta configuration. To switch to Delta you just have to connect the terminals as shown However such a manual rearrangement of terminals is practically difficult in practice in order to achieve this, we use contactors. Use of contactors are simple, just draw three cables from the second end of the terminal If these three cables are connected together it is clear that it will result in a star connection This is exactly what a contactor does When this contactor is activated that will result in a star connection To achieve Delta connection the second terminal cables are branched and one more contactor is introduced The second Branch is connected to the input supply as shown So if the second contactor is closed it will result in a delta configuration. The exact timing of contactor action is determined by a timer We hope you developed a clear insight it to start all the connections Please help us at patreon.com so that le can achieve its goals. Thank you

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100 Replies to “Understanding STAR-DELTA Starter !”

  1. If at the start of the spinning the coils and the rotor act like a transformer , does it mean you can get shocked through the rotor ?

  2. You explained a 9 wire Star-Delta configuration. But there is more. There's 6 and 12 wire connection that could be explained.

  3. Thats why when a 3 phase ac motor starts
    The current rises to 500 Amps and gradually drops to 150 Amps as it’s gaining speed
    If you put some metal bars across the Terminal on the induction motor as it starts
    The metal bars will melt

  4. Great presentation!
    Now please explain how Russian developed electric motors that runs on star and delta at the same time with no switches.

  5. To describe the teaching style of this video, is like getting nervous as I might just reveal too much.

  6. Thank you very much, i've finally understand how contactor works including the star and delta connection.

  7. Moo moo says; I'm confused here. My 1945 harvard mechanical engineering book says Delta Star is for 4 wire transmission lines, as its more efficient at less current loss and thusly transfers more juice down the big ass transmission line. Here you showed 3 phase wireing as I see it. Good show on the motor physics and magnetics and current flow data. I am impressed by the whole presentation and "duh" got the picture damn straight. I tend to stick my nose as an ex-mechanic right where it don't belong and I thank you for this show mucho.

  8. At 4:49, suppose if we give input powers to left side terminals(u2,v2,w2) instead of right side, What will happen? Will it be called short circuit then?, Bcoz, we are having technical argument over here.

  9. Thanks a lot….
    Shame on the education system and the lecturers who teach us mammoth syllabus but don't teach practical and fundamental knowledge which we need all life.
    When we reach industry we are ashamed by practical knowledge guys ITI, DIPLOMA.

    Knowledge without practical application is blind.

  10. Yeah! Good tutorial, very well explained, but what the fucking goes on with or without capacitator. 🙄

  11. hi, thanks for the video illustration, i m fresh graduate. i have a question about the star delta connection as u discussed at 4:40, when the coil of the motor are connected in star, u left the ground unconnected or grounded??? any reason why???? thanks 🙂

  12. _rotE==_dB/dt and rotH==J+dD/dt and HrotE–ErotH==div(H*E) ==power engine_motor ellectric identic for difuzion ellectric sound bass _ __archaicxn lord

  13. Bro I have seen tons of videos and even went to school for this. Your video is more valuable than all previous resources I have encountered. Great job man.

  14. I guess I didn't pay attention in premed physics-lol. I thought AC motors meant that the coil continuously attracts the rotor instead of repelling (like in a DC motor)

  15. It’s amazing the things that y’all teach. I’m an ME major and work in natural gas transmission as an engineer. I dig yalls videos.

  16. That was amazing… I mean really amazing.. During all my study and career I knew the motors draw huge starting current but never knew why they do so.. Thanks to you…

  17. Still there are 900 people who disliked this movie. If you still have no idea about the content after watching this crystal clear movie, it is not the movie to blame fella.

  18. I am an EE Engineer and no one has ever explained this crystal clear… Can see great efforts behind this video. Congratulations.. 👏

  19. in this video for star delta starter only 2 contactor and on timer is used , is it possible to make star delta starter by using 2 contactor and a timer

  20. good animation rotE=_dB/dt and rotH=J+dD/dt and HrotE–ErotH=div(H*E) is power ellectric generator_motor and speak_ difuzor sound _thank you _archaicxn lord

  21. Как вы заебали "вращающееся" – ПУЛЬСИРУЮЩЕЕ магнитное поле показывать вращающимся!!!!

  22. Sir Agar Hindi mein mil jaaye Tu To Ham bhi join kar le please share reply Hindi medium Ho To Ham bhi Jarur join Karenge

  23. Just shows how much bull shit they (teach) you in uni, what a fucking waste of time and money. Who has leant more by experience than class here?

  24. how we can say that reducing input voltage mean reducing the current in the stator? because current on the star connection is the same ,,I line = I phase ,,,, and Why the squirrel cage bars are designed at some angle ,,what if straight ?

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