Salient pole alternator
Smooth cylindrical pure alternator
Projected pole alternator
Impulse turbo alternator
KVA
KW
KVAR
KWH
Must be same
Must be different
Must be low
Must be high
Frequency must be same
Voltage must be different
Sequence must be different
Polarity must be different
To get more voltage
To share more loads
To improve efficiency
To maintain constant frequency