How Does Brushless Alternator Works? (With Diagram)

Operation Principle of Brushless Alternator
              In all alternators, voltage may be generated by rotating a coil wire in the magnetic field or by rotating a magnetic field within a stationary coil wire .It doesn't matter whether the coil is moving or the magnetic field is moving. Either configuration works equally well and both are used separately or in combination depending on mechanical, electrical and other objectives.

              In the case of brushless alternator both combinations are used
together in one machine.
             Before going to the explanation part you should know about stator,rotor,field windings and armature. The stationary part of an alternator is called the stator and the rotating part is called the rotor. The coils of wire used to produce a magnetic field are called the field winding and the coils that the power are called the armature winding. Here you can see both Armature and Field winding used as rotor as well as startor.


Working Of Brushless Alternator

          Brushless alternators have two parts; one is Excitation alternator part and the other is  main alternator part 

Here we have provided a schematic diagram of Brushless Alternator

Excitation alternator
       Here Armature is rotor and  Exciter Field winding is stator. Exciter field produce a magnetic field by the help of AVR or Residual magnetism. When it starts rotating a voltage is generated in Exciter armature which gives current to the main field to produce magnetic field in Main alternator.

Main Alternator
.      Here main field is rotor and armature is stator. Voltage Produced in the exciter armature pass through the Diode Mounting plate(Rectifier) and goes to the Main Field which produce a magnetic field. When this magnetic field cuts the Main Armature a potential difference is procured. we can take supply out directly, no brushes required . Here the voltage produced can be regulated by exciter field current

AVR(Automatic Voltage Regulator)
       Avr controls the Output voltage by controlling exciter field current. AVR , sensing the out put voltage from main armature , compares it  with the set value and then changes the exciter field current. AVR having diodes which converts A/c into D/c for exciter field 
 3-Phase Brushless Alternator Circuit Diagram




27 Comments


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  1. how does the exciter field i.e the exciter stator gets charged initially ?

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    Replies
    1. residual magnetism ie,when the power is switched off to an electro magnet, it will retains some magnetic power

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    2. Sometimes there is one permanent magnetic and two electromagnets which start the process

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    3. Exciter field consists of 1 permanent magnetic and two electromagnets... https://www.flight-mechanic.com/wp-content/uploads/2020/06/12-324.gif

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    4. So Ive been reading and watching a lot of videos online converting old brushed alternators into a brushless DC motor using a Bldc controller to energize the three phase coils and a low voltage power source as an excite through the old brushes. My question is... Can this same set up or a simlar set up be used to turn the brushless alternator into a Brrushless motor... what would be the advantages and disavantages of this approach.

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  2. Replies
    1. automatic voltage controller

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    2. Residual magnetism or it has a battery supply to...increase the residual magnetism ...so that req volatage can be produced

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    3. After alternators are manufactured, they have no magnetism at all. The exciter stator(exciter field) is temporarily (for few seconds) energized by external 12V battery with the rotor running. Exciter field and main field become electromagnets. The exciter field and main field retain the magnetism till the next operation and there will be no need for external battery use. Little Emf will be induced on main armature and voltage will be tapped on its terminals to the AVR. The AC current flowing to the AVR is rectified and regulated (increased or decreased) to the level that matches required output voltage level then fed to exciter field. This is a closed loop control system. It gives feed back which is inturn used as ref.

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    4. Thank you very much @Hlomza, @bijoy.. This is what i was looking for almost a day in all the sites, the explanation gave me the clarity now.

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  3. Why diode plate is fitted in between exciter armature and main field.exciter armature is already excited and connected on same shaft?

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    Replies
    1. Yes you are correct exciter armature get excited and produce A/C, Diodes convert this A/C to DC for the Main field

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  4. can someone help me ? i get an assignment about 'explain the principle of operation of a brushless type DC altenator' so is this the answer im searching for ?

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    Replies
    1. Operations are same, but at the out put thr will probably have 6 diodes to convert the output from the main alternator to DC.

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  5. 1.Initially Residual magnetism will be in exciter field or main field?

    2.Does Exciter stator or field is made up of permanent magnet?

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    Replies
    1. 1. both exciter field and main field having residual magnetism
      2. No

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  6. how to connect a GAVR-25A to a single phase brushless generator?

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  7. Greatly explained, no doubts at all

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  8. Hi, does brushless alternator is the same as we see in automobile alternators, or Is it that you are referring to you is Permanent magnet Alternator?

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  9. Also is the torque requirements same as that for a normal alternator and an Permanent magnet Alternator?

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  10. Inside the rotor wheee the claw is, are there suppose to be windings inside the claw as well?

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  11. How we get output of the alternator practically, explain please

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