Parameters of an alternator

Replies

• 

  grsalvi

  EMF induced in transformer (voltage output of transformer)
  The theoretical equation is
  E(phase)=4.44*(frequency)*(flux per pole)*(total number of coils).
  
  Though above equation tells what will be the emf induced in each phase of an alternator, lets see what is practically deciding the voltage generated.
  
  You know an alternator works on principle that "when ever the flux linking with a coil is changed ,an emf is induced in the coil".
  
  That's it , the parameters which decide the emf induced in Alternator are :
  a]the flux per pole
  b]number of coils ,since more coils more conductors cut flux ,hence more emf induced.
  c]rate of change of flux, which directly dependent on the RPM on alternator.
• 

  Jeffrey Arulraj

  Alternator has input DC source which generates a mechanical work Which is converted back into AC source
  
  DC is converted into AC in an alternator right pure mech energy is not transferred directly in an alternator
  
  Always the load current is determined by speed in motors not sure about that in an alternator
• 

  grsalvi

  And yes the second part the current flow of alternator is dependent on the load you apply to alternator.
  Increase load ,current increases .As in motors ,mentioned by Conqueror above.
• 

  lal

  Conqueror

  Alternator has input DC source which generates a mechanical work Which is converted back into AC source
  
  DC is converted into AC in an alternator right pure mech energy is not transferred directly in an alternator
  
  Always the load current is determined by speed in motors not sure about that in an alternator

  I would like to disagree. Infact mechanical energy is what gets converted to alternating electrical energy in an alternator. The DC source used in alternators is just used to energise the field. By just energising the field an alternator cannot provide an AC output. For that, the field is rotated to make a varying flux by means of mechanical energy. So actually, its completely the mechanical energy that gets converted to electrical energy at the output.
  
  Current and voltage are dependent to each other. The ratio of voltage and current is a constant, V/I = Z (impedance). When one varies, the other follows to keep the ratio constant for a particular load (impedance). Higher load means lower impedance and vice-versa.
• 

  Jeffrey Arulraj

  Thanks for clearing it out #-Link-Snipped-# now pretty clear about alternator
• 

  ABCD ABCD

  nice question zaveri, had the same time ago. But, number of coils will be three for 3-phase alternator. Err?
  But, what is responsible for frequency of the AC generated?
• 

  lal

  Frequency of the generated AC is goverened by the number of poles and speed of rotor.
  
  f = NP/120
  N = speed in rpm
  P = number of poles
  
  Once a machine is made, its poles will not be changed. So it is safe to say, speed controls the frequency.
• 

  ABCD ABCD

  lal

  Frequency of the generated AC is goverened by the number of poles and speed of rotor.
  
  f = NP/120
  N = speed in rpm
  P = number of poles
  
  Once a machine is made, its poles will not be changed. So it is safe to say, speed controls the frequency.

  Thanks, can you give the source(or book) of this information? I'm interested in reading more about this.
• 

  lal

  mreccentric

  Thanks, can you give the source(or book) of this information? I'm interested in reading more about this.

  Refer any book on electrical machines. Or try the vast web. There are numerous quality sources available on the internet.
• 

  ABCD ABCD

  lal

  Refer any book on electrical machines. Or try the vast web. There are numerous quality sources available on the internet.

  BTW, which book did you refer? I have one will go and check if this is there.
• 

  lal

  I use 'Theory and Performance of Electrical Machines' by J. B. Gupta.
  
  Any text book on Electrical Machines sure will have that theory.
• 

  pinank

  mreccentric

  BTW, which book did you refer? I have one will go and check if this is there.

  you can use Electrical Machines by PS Bhimbra...