DC GENERATOR CHARACTERISTICS
- 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:
- 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…….