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How does self excited generator starts ?

A self-excited generator is a type of DC generator that initiates its own field excitation to generate electrical power. The process of starting a self-excited generator involves creating an initial magnetic field within the generator’s field winding. Here is a detailed explanation of how a self-excited generator starts:

  1. Components of a Self-Excited Generator:
    • A self-excited generator consists of a rotor (armature), a stator (field winding), brushes, and a commutator. The field winding is a coil of wire wound around the stator, and the rotor consists of a coil of wire connected to a commutator.
  2. Initial Conditions:
    • Initially, the generator is at rest, and there is no magnetic field in the field winding. Therefore, there is no induced electromotive force (EMF) in the armature.
  3. Manual Rotation or External Voltage:
    • To initiate the starting process, the rotor may be manually rotated to create an initial magnetic field. Alternatively, an external voltage source can be applied to the field winding to induce a small initial magnetic field.
  4. Induced EMF in the Armature:
    • As the rotor starts to turn or an external voltage is applied, a small induced EMF is generated in the armature coil due to the changing magnetic field.
  5. Current Flow in the Field Winding:
    • The induced EMF in the armature causes a small current to flow through the field winding. This initial current establishes a weak magnetic field around the field winding.
  6. Regeneration Process:
    • The weak magnetic field induces a slightly larger EMF in the armature. This induced EMF further increases the current flowing through the field winding, thus strengthening the magnetic field.
  7. Positive Feedback Loop:
    • This process continues, creating a positive feedback loop. As the magnetic field strength increases, so does the induced EMF in the armature, leading to a higher current flow in the field winding and a stronger magnetic field.
  8. Saturation:
    • The process continues until the magnetic field saturates, reaching a point where further increases in the field current do not significantly enhance the field strength.
  9. Steady-State Operation:
    • At this point, the generator has reached steady-state operation. The self-excited generator is now capable of generating a stable and continuous electrical output without the need for an external voltage source.
  10. Voltage Regulation:
    • The generated voltage can be regulated by adjusting the resistance in the field circuit. This helps maintain a constant voltage output under varying load conditions.

In summary, a self-excited generator starts by establishing an initial magnetic field within the field winding through manual rotation or an external voltage source. The induced EMF in the armature initiates a positive feedback loop, gradually building up the magnetic field strength until the generator reaches steady-state operation, producing a stable electrical output.

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