Parallel operation of Alternators

Parallel operation of Alternators 

the process of  connecting an alternator in parallel with another, then alternator is called synchronizing.

Advantage of parallel operation of Alternators 

The various advantage of running alternator in parallel




1. better continuity of power supply-can be maintained running a single unit.

2. It gives maximum efficiency , because of running at full load

3. Repairing of a unit  is more convenient and economical

4. the additional unit can be installed and when required with the increase  of load

5. the cost of stand by unit is less.

Condition for parallel operation 

1. The voltage of both the alternators must be same. the incoming voltage of the alternator to be
synchronized and the running voltage of the bus bar must be same.

2. the frequency must be same

3. the phase sequence must be same

Method of synchronizing or parallel operation of alternator

the following are the method of the parallel operation

1. Dark lamp method

2. Bright lamp method

3. Dark and Bright lamp method

4. synchronoscope method

Equipment required for parallel operation of Alternator 

1. Double range voltmeter

2. Double range frequency meter

3. Synchroscope

4. Lamps for Dark and bright lamp method

Load sharing of Alternator

1. By changing the excitation  of current

2. By increasing the steam supply of one Alternator

Why Alternator paralleling ?

1. At the junction point voltage must be same even though not the same at the Alternator

2. At the junction point the phase sequence for three phase must be same

3. The incoming machine must be in phase at the moment of parallel point.

4.  At the paralleling point the line frequencies must be identical. In vast majority of cases,means the same frequency changing is not economic.

5. the prime-movers must have relatively similar and dropping speed-load characteristics.