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.
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.
the alternator having 3 characteristics , they are given below,
- 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,
- open circuit characteristics (OSC)
- 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.