This document discusses different types of DC generators, including permanent magnet, separately excited, and self-excited generators. It focuses on self-excited DC generators, which can be series wound, shunt wound, or compound wound. The document provides details on the magnetic or open circuit characteristic curve, which shows the relationship between field current and generated voltage without a load. It also discusses the internal and external characteristic curves when the generator is loaded, accounting for voltage drops due to armature reaction and ohmic losses. Characteristics of series wound and shunt wound generators are covered as well.

1. DC GENERATOR
CURVE
BY, ABHINABA
GHOSH

2. TYPES OF GENERATOR:
• FIELD COILS EXCITED BY PERMANENT MAGNETS – PERMANENT MAGNET DC
GENERATORS
• FIELD COILS EXCITED BY SOME EXTERNAL SOURCE – SEPARATELY EXCITED DC
GENERATORS
• FIELD COILS EXCITED BY THE GENERATOR ITSELF – SELF EXCITED DC
GENERATORS

3. SELF EXITED GENERATOR:
• ACCORDING TO THE POSITION OF THE FIELD COILS THE SELF-EXCITED DC
GENERATORS MAY BE CLASSIFIED AS…
• A. SERIES WOUND GENERATORS
• B. SHUNT WOUND GENERATORS
• C. COMPOUND WOUND GENERATORS
COMPOUND WOUND GENERATORS ALSO OF
2 TYPES:
a. COMMUTATIVELY COMPOUND WOUND

4. SERIES AND SHUNT WOUND:

5. COMPOUND WOUND:

6. CHARACTERISTIC OF SEPARATELY EXCITED
DC GENERATOR
• MAGNETIC OR OPEN CIRCUIT CHARACTERISTIC
• THE CURVE WHICH GIVES THE RELATION BETWEEN FIELD CURRENT (IF) AND THE GENERATED
VOLTAGE (E0) IN THE ARMATURE ON NO LOAD IS CALLED OPEN CIRCUIT CHARACTERISTICS
• THE PLOT OF THIS CURVE IS PRACTICALLY SAME FOR ALL TYPES OF GENERATORS, WHETHER THEY
ARE SEPARATELY EXCITED OR SELF-EXCITED.
• THIS CURVE IS ALSO KNOWN AS NO LOAD SATURATION CHARACTERISTIC CURVE OF DC
GENERATOR.

7. OTHER CHARACTERISTICS:
• WHEN THE GENERATOR IS LOADED THEN THE VOLTAGE DROPS DUE TO TWO MAIN
REASONS-
• 1) DUE TO ARMATURE REACTION,
• 2) DUE TO OHMIC DROP ( IARA ).
INTERNAL CHARACTERISTICS:
THE INTERNAL CHARACTERISTIC OF THE SEPARATELY EXCITED DC GENERATOR IS
OBTAINED BY SUBTRACTING THE DROPS DUE TO ARMATURE REACTION FROM NO
LOAD VOLTAGE. IT IS A EG VS IF CURVE.
EXTERNAL CHARACTERISTICS:
• HE EXTERNAL CHARACTERISTIC OF THE SEPARATELY EXCITED DC GENERATOR IS
OBTAINED BY SUBTRACTING THE DROPS DUE TO OHMIC LOSS ( IA RA ) IN THE
ARMATURE FROM GENERATED VOLTAGE ( EG ).
• TERMINAL VOLTAGE(V) = EG - IA RA.

8. THE CURVE:

9. CURVE FOR SHUNT WOUND:

10. CHARACTERISTICS OF SERIES WOUND:

11. • THAT IS WHY SERIES DC GENERATOR IS CALLED CONSTANT CURRENT DC
GENERATOR.
• FOR SHUNT WOUND LOAD RESISTANCE OF THE MACHINE MUST BE MAINTAINED
PROPERLY.

12. • THANK YOU…….