The two methods of synchronising an alternator are? 

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ALP CBT 2 Electrician Previous Paper: Held on 22 Jan 2019 Shift 3
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  1. Loading effect and phase sequence
  2. Lamp method and synchoroscope method
  3. Two bright and one dark lamp method
  4. Hysteresis loss and friction loss method

Answer (Detailed Solution Below)

Option 2 : Lamp method and synchoroscope method
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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.

Before connecting an alternator into the grid, the following conditions must be satisfied:

Equal voltage: The terminal voltage of incoming alternator must be equal to the bus-bar voltage.

Same frequency: The frequency of generated voltage must be equal to the frequency of the bus-bar voltage.

Phase sequence: The phase sequence of the three phases of alternator must be similar to that of the grid or busbars.

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:​

  • Three Dark Lamps Method
  • Two Bright, One Dark Method
  • Synchroscope Method
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