Alternator basic characteristics- what we needs to know.

Alternator Rating:

Generally the alternator are nothing but AC generator. so the alternators are producing AC voltages. normally alternator rating voltage ,current, frequency and speed  all are designed by manufacturer. but the power factor of alternator can not be designed by manufacturer because they don’t know the nature of connecting load . that’s why alternator always designed for KVA rating not in KW.


The alternator output current is always depend on the armature heating loss. when the heating loss if its high it will damage the insulation of alternators. The heating loss generally called as I2R loss or coper loss. the output voltage of the alternator is depend on the rotating speed of the alternators.

N= 120f/p

the  speed of the alternator is already designed by the manufacturer it cant be changed. for small ratings of alternator rated in volt ampere VA. the mostly all characteristics alternator ratings is build with name plate on the alternators.


Alternator characteristics

the alternator having 3 characteristics , they are given below,

  1. output current with speed of alternator

If speed of the alternator is decreased then output current of the alternator also decreased. so speed and output current of alternators both are directly proportional.

2. efficiency with speed of alternator

If speed of the alternator running  lower then rated speed then efficiency of the alternator will be reduced .

3. current drop with increasing alternator temperature.

The output current of the alternator is depend on the temperature produced by armature in the alternators. if temperature increased then out put current of alternator will be reduced.  because the output current of alternators and temperature of armature both are indirectly proportional.

other some important characteristics of alternators are,

  1. open circuit characteristics (OSC)
  2. short circuit characteristics (SCC)

open circuit characteristics:

its drawn between  the open circuit voltage and filed current If.

Short circuit characteristics:

Its drawn between the short circuit current and field current If.





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