Design of field regulators for dc shunt generators

Design of field regulators for dc shunt generators

• 1.
  Name:- Nisarg Amin Topic:-Design Of Field Regulators for DC Shunt Generators 1
• 2.
  Function • The functionof field regulators in case of DC shunt generators is to control the value of field current thereby controlling the terminal voltage of the generator. • The generated EMF in a DC generator is:        A P 60 ZN Eg Eg NEg  NKEg 
• 4.
  • From theabove equation, it is clear that the generated EMF is directly proportional to the product of flux per pole and speed. • If generator runs at constant speed then the generated EMF is directly proportional to the flux per pole and hence to the field current If. • The terminal voltage on load: V = E - IaRa
• 5.
  • With theincrease in load current, terminal voltage will slightly decrease due to the ohmic drop in the armature and due to armature reaction. • This decrease in terminal voltage under load can easily be neutralized by increasing field current slightly and therefore constant terminal voltage can be maintained.
• 6.
  • A D.C.shunt generator should maintain a constant voltage across its terminals irrespective of the magnitude of load being supplied by it. • It is not easy to control the speed of armature in a D.C. shunt generator except by varying the speed of the prime mover.
• 7.
  • So, itI s undesirable to regulate the terminal voltage of a generator by variation of speed. • Therefore it is customary to vary the magnetic flux for this purpose. • This can be easily by inserting a variable or adjustable resistance in series with the main field circuit as shown in figure
• 8.
  • This permitsa wide range of control of induced EMF. • This variable or adjustable resistance is called the shunt field regulator.