Q7

 

Alternators of different numbers of poles

There are two alternators having similar rating in all respect except numbers of poles. One is four pole machine whereas other is six pole machine. Is it feasible to synchronize them for parallel operation?

Answer

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   Answer

Both machines have identical ratings. Rated Voltage is same. Means they run at different RPM. Four pole machine run at 1500 RPM and six pole machine run at 1000 RPM for 50 Hz system. Numbers of pole depends on speed of its prime mover. Alternator of thermal power plant is two poles as steam turbine speed is 3000 RPM. Alternators of hydro power plant have more poles as water turbine speed is very low around 60 to 150 RPM.

Relation is known as 60 × frequency / pair of poles = RPM.

Thermal and Hydro generators are running parallel in the grid system.