If the series field ampere turn are such as to produce the same voltage at rated load as at no load then the generator is flat compound wound generator.
OVER COMPOUND WOUND:
If the series field ampere turn are such as to produce the voltage at rated load as grater then the no load then the generator is over compound wound generator.
UNDER COMPOUND WOUND:
If the series field ampere turn are such as to produce the voltage at rated load as laser then the no load then the generator is under compound wound generator
The field winding of the generator is disconnected from the machine and connected to an external DC power supply. The field or exciting current If is varied and value read on Ammeter A. The machine is derived at constant speed by the prime mover. Ifisincreased by suitable steps & the corresponding value of Eo are measured. On plotting the relation between If & Eo a curve is obtained and that is the O.C.C curve.
IMPORTANCE OF O.C.C CURVE:
1. The O.C.C or No-Load saturated curves for Self-Excited generator whether shunt or series connected, are obtained in a similar way.
2. O-A is called Residual voltage.
3. Due to Residual magnetism in the poles, some e.m.f [=OA] is generated even when [If = 0]
4. After point B saturation of poles starts.
5. O.C.C for a higher speed would lie above this curve and vice versa.
OVER COMPOUND WOUND:
If the series field ampere turn are such as to produce the voltage at rated load as grater then the no load then the generator is over compound wound generator.
UNDER COMPOUND WOUND:
If the series field ampere turn are such as to produce the voltage at rated load as laser then the no load then the generator is under compound wound generator
The field winding of the generator is disconnected from the machine and connected to an external DC power supply. The field or exciting current If is varied and value read on Ammeter A. The machine is derived at constant speed by the prime mover. Ifisincreased by suitable steps & the corresponding value of Eo are measured. On plotting the relation between If & Eo a curve is obtained and that is the O.C.C curve.
IMPORTANCE OF O.C.C CURVE:
1. The O.C.C or No-Load saturated curves for Self-Excited generator whether shunt or series connected, are obtained in a similar way.
2. O-A is called Residual voltage.
3. Due to Residual magnetism in the poles, some e.m.f [=OA] is generated even when [If = 0]
4. After point B saturation of poles starts.
5. O.C.C for a higher speed would lie above this curve and vice versa.