Why is it not necessary to flash the field of a DC alternator after it has been overhauled?

Why is it not necessary to flash the field of a DC alternator after it has been overhauled?

• A. The field is excited by battery current, and residual voltage is not used to start producing current.
• B. The residual voltage is used to start producing current.
• C. The field winding is a permanent magnet.
• D. The alternator starts without any excitation.

Answer: (A)

The field winding of a DC generator (alternator) creates the magnetic flux that makes current flow. That flux comes from current in the field windings, which is supplied by the excitation system from the battery through the regulator. When the engine is turning, this excitation gets the field established so the generator can produce output immediately. Residual magnetism is not relied upon to start producing current, especially after an overhaul, because it’s weak and unreliable compared to a properly excited field. So, after overhaul, you don’t need to flash the field because the field can be reliably excited from the battery/voltage regulator, providing the necessary magnetic field to generate output as soon as rotation begins.

The field winding of a DC generator (alternator) creates the magnetic flux that makes current flow. That flux comes from current in the field windings, which is supplied by the excitation system from the battery through the regulator. When the engine is turning, this excitation gets the field established so the generator can produce output immediately. Residual magnetism is not relied upon to start producing current, especially after an overhaul, because it’s weak and unreliable compared to a properly excited field.

So, after overhaul, you don’t need to flash the field because the field can be reliably excited from the battery/voltage regulator, providing the necessary magnetic field to generate output as soon as rotation begins.