How do the synchronizing lamps indicate the correctness of phase sequence between existing and incoming Alternators?

The correctness of the phase sequence can be checked by looking at the three sets of lamps connected across the 3-pole of the synchronizing switch. If the lamps grow bright and dark in unison it is an indication of the correctness of the phase sequence. If on the other hand, they become bright and dark one after the other, connections to any two machine terminals have to be interchanged after shutting down the machine.

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State the condition to be satisfied before connecting two alternators in parallel

The following are the three conditions to be satisfied by synchronizing the additional Alternator with the existing one or the common bus-bars.

• The terminal voltage magnitude of the incoming Alternator must be made equal to the existing Alternator or the bus-bar voltage magnitude. 
• The phase sequence of the incoming Alternator voltage
• The phase sequence of the incoming Alternator voltage must be similar to the bus-bar voltage. 
• The frequency of the incoming Alternator voltage must be the same as the bus-bar voltage. 

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What are the causes of changes in voltage in Alternators when loaded?

Variations in terminal voltage in Alternators on load condition are due to the following three causes:

• Voltage variation due to the resistance of the winding, R
• Voltage variation due to the leakage reactance of the winding, Xt
• Voltage variation due to the armature reaction effect, Xa

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How does electrical degree differ from mechanical degree?

Mechanical degree is the unit for accounting the angle between two points based on their mechanical or physical placement.

Electrical degree is used to account the angle between two points in rotating electrical machines. Since all electrical machines operate with the help of magnetic fields, the electrical degree is accounted with reference to the magnetic field. 180 electrical degree is accounted as the angle between adjacent North and South poles.

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