How does an Alternator Work ?

How does an Alternator Work ?

Alternators are the workhorse of the power
generation industry. It is capable to generate AC power at a
specified frequency. It is also called as synchronous
generator. Electricity is produced in alternators
by Electromagnetic Induction. To generate electricity in a coil, either the coil should rotate with respect to magnetic field or a magnetic field should rotate with
respect to the coil. In the case of alternator the latter
approach is used. Rotor and armature coils are the two main
parts of an alternator. The rotor produces a rotating magnetic flux. Armature coils are stationary and rotating magnetic flux associated
with the rotor induces electricity in the armature
coils. This kind of rotor shown here is known as
salient pole rotor. For gaining better insight of its working let’s consider a rotor with just four poles ‘Rotor coils are excited with a DC power source. Magnetic field produced around it would
be a shown. The rotor is made to rotate by a prime
mover. This makes the rotor flux also rotate
along with it, at the same speed . Such a revolving magnetic flux now intersects armature coils, which is fitted around the rotor. This will generate an alternating EMF across the winding. Here is a slowed down version of the rotor stator interaction. For this four pole system when the rotor turns half revolution, induced EMF takes one complete cycle. It can be easily established that,
frequency of induce EMF, rotor speed and number of poles are connected through following relationship: It is clear here that, frequency electricity produced is synchronized with mechanical rotational speed. For producing 3 phase AC current, two more such armature coils which are in 120 degree phase difference with the first is put in the stator winding. Generally one end of these three
coils are Star connected, and three phase electricity is drawn
from the other ends. It is clear from this equation that, in order to produce 60-hertz electricity a 4-pole rotor should run at following RPM. Such huge rpm will induce a tremendous
centrifugal force on polls of the rotor, and it may fail mechanically over the time. So salient polel rotors are generally
having 10 to 20 polls, which demands lower RPM. Or salient pole rotors are used when the prime mover rotates at relatively lower RPM. Pole core is used to effectively transfer the magnetic flux, and they’re made with fairly thick steel lamina. Such insulated lamina reduce energy
loss due to eddy current formation. Armature winding of three-phase, 12 poll system is shown here. A stator core is used to enhance the magnetic flux transfer. DC current is supplied to rotor via a
pair of slip rings. DC current is supplied from an external source or from a small DC generator which is fitted on the same prime mover. Such alternators are called self excited. With variation of load, Generator terminal output voltage will vary. It is desired to keep the terminal voltage in a specified limit An automatic voltage regulator helps in
achieving this. Voltage regulation can be easily
achieved by controlling the field current. If the terminal voltage is below the desired
limit, AVR increases the field current, thus the field strength. This will result in an increase in
terminal voltage. If terminal voltage is high, the reverse is done. We hope you had a nice introduction on the working of alternators. Thank you !

About the Author: Michael Flood


  1. This is possible or not? In generator stator side we give AC input so as time varying magentic field is vary and so chainging magnetic flux is Link with armature and emf is produced So here there is no need to rotate the rotaer to turbine?

  2. Energy from magnet can be obtained without any mechanical movement. All we need is material capable of being converted from magnetic to nonmagnetic when applying electrical impulses. This will simulate the rotation of the armature in the generators. Such a material was created for other purposes and there is technology. More info ?

  3. Okay so does the small DC alternator on the far right make energy for the alternator Main Power's Magnetic field?

  4. why does the outside remain stationary? can you also spin the outside opposite from the inside?

  5. السلام علیکم و رحمت اللہ و برکاتہ
    Thank you sir
    My WhatsApp number

  6. I request you to also show the subtitles because of your American accent​ sometimes it become difficult to figure out some words.

  7. For constant freq. the prime mover needs to run at constant speed. what if the prime mover turns at slow speed? AVR?

  8. __rot E==dB/dt and rotH==J+dD/dt and HrotE–ErotH==div(H*E) and where is it this here…?? in work of alternator_engine_motor of ellectric power but this formula is not here videoclip describe_ ____archaix lord

  9. Good video, but the audio seems to have some weird glitches. Also, it sounds like the writing was done by a non-native English speaker because there are some odd errors.

  10. How much DC voltage do you need for your rotor so that it can produce an electro magnetics field?

  11. i had a idea for a electric vehicle with five wheels? use the fifth wheel to turn the alternator and charge the battery while driving? 🤔🚗🔋🤷‍♂️ (with a step down transformer and a rectifier) 🤗

  12. Nice

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  13. So to turn a car alternator into a motor you need to apply ac current to the coils, and dc current to the brushes?

  14. How is each phase regulated separately? Say you put a large load on only one phase so you need to bump up the magnetic coil voltage, will that cause the other 2 phases to have too high a voltage? Or do you just regulate based on the average voltage and slight imbalances are just tolerated? The more loads on the system the more balanced it will be so it will probably matter less.

  15. The dude conveniently threw a fancy word with the slightest thought. "Prime Mover". Sounds like God. Get off this kind of monopoly over knowledge. Now I have to go to some other video and listen to their none sense to find out what is meant by Prime Mover. Then that dude will throw in some other word that I have to look up. This is the kind of garbage that makes learning a playground of people's big fat ego. Yea you are the greatest.

  16. How bizarre. No wonder it is a circus. Armature coil is stationary and the rotor turns with its winding creating a rotating magnetic field.
    Okay, another sucker comes along and says it like this: Armature ( which is made of rotor and windings) turns inside a stator. The stator has coils which are stationary. As the armature turns changing magnetic field is created which causes the current in the coil of the stator. That current is drawn from the stationary winding of the Stator.

  17. Terrible video. The regulator regulates the voltage by controlling the current to the coil. is what he says at around 5 minutes at the end of the video. Yet he never shows the coil and where is the wire that feeds current to the coil. However, the so-called armature coil is the output, not input. and the rotor wires is what gets current from the little self-starting generator he calls it. That self-starting generator makes no sense at all. It won't produce shit the way it is and is hooked up to the brush man. Take this goddam video out of here.

  18. Hi,

    Rotation required in alternator..
    Because if both stator and rotor stable position also AC supply will
    Create rotating magnetic field like
    Induction motor.

    So we can generate emf by using this rmf concept?

  19. Can you do video about Car's alternator & explain AVR circuit in detail. And disadvantage of pm rotor in alternator.

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  21. H#N*I/l and rotE#_dB/dt+rot(v*B) and rotH#J+dD/dt and HrotE–ErotH#div (H*E) is lex maxwell for electromagnetyc force from generator and ellectric motor __archaicxn lord

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