If a stationary alternator is connected to a live bus bar, then ______.

A stationary alternator is never connected to live bus bars because it will result in a short circuit in the stator winding (since there is no generated emf yet).

Synchronization of Alternator:

• Synchronization of alternator means connecting an alternator into the grid in parallel with many other alternators, that is in a live system of constant voltage and constant frequency.
• Many alternators and loads are connected to a grid, and all the alternators in the grid are having same output voltage and frequency (whatever may be the power).
• It is also said that the alternator is connected to an infinite bus bar.
• It is not a practice to connect a stationary alternator to a live busbar. Under a stationary condition, the emf induced in stator winding is zero.
• If such an alternator is connected to a live bus bar, there is always a danger of short circuit as armature resistance is negligible, and reactance is zero (frequency is zero).
• Before connecting an alternator to the grid, the following conditions must be satisfied:

1. Equal voltage: The terminal voltage of the incoming alternator must be equal to the bus-bar voltage.
2. Similar frequency: The frequency of generated voltage must be equal to the frequency of the bus-bar voltage.
3. Phase sequence: The phase sequence of the three phases of the alternator must be similar to that of the grid or bus bars.
4. Phase angle: The phase angle between the generated voltage and the voltage of the grid must be zero.

• The first condition of voltage equality can be satisfied by a voltmeter.
• To satisfy the conditions of equal frequency and identical phases, one of the following two methods can be used:
  • Synchronization using incandescent lamp
  • Synchronization using a synchroscope.