This document discusses direct current (DC) generators. It includes a list of group members and sections about the principle and construction of DC generators. The types of generators are identified as separately-excited, self-excited, shunt wound, series wound, and compound wound. Losses in DC generators including copper, iron, mechanical, stray and brush contact resistance losses are defined. Power stages and efficiencies including mechanical, electrical, overall and maximum are explained. Diagrams and an example of a power stage are provided.

1. Welcome
D.C. Generators....

2. Group members
• Md. Emdadul Haque ID : 151-19-1687
• Md. Golam Rabbi ID : 151-19-1719
• Md. Nahid Hasan ID : 151-19-1644
• Naeim Khan ID : 151-19-1639
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3. D.C. Generators
•Principle & working
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4. Construction
}Yoke
}Poles and pole shoes
}Field winding
}Armature core
}Armature winding
}Commentator and
brushes

5. Working Principle
Working
Principle
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6. Types of generators
• A)Separately-excited generators;
• B)Self-excited generators.
i. Shunt wound;
ii. Series wound;
iii. Compound wound
(a)Short-shunt compound wound.
(b)Long-shunt compound wound.
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7. Diagram
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8. Total loss in a D.C. generator
Total loss
Copper losses Iron losses Mechanical losses
(a)Armature Cu loss (a)Hysteresis loss (a)Friction loss
(b) Shunt Cu loss (b)Eddy current loss (b)Windage loss
(c)Series Cu loss
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9. Copper losses
Armature Cu losses=ia2Ra
*This loss is about 30 to 40% of full-load losses
Shunt Cu losses=ish2Rsh
Series Cu losses=ise2Rse
*This loss is about 20 to 30% of F.L. losses.
Loss due to brush contact resistance.
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10. Stray Losses
•Magnetic and mechanical losses are
collectively known as Stray losses. These
are also known as rotational losses for
obvious reasons.
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11. Power Stages in D.C. Generator
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12. An Example of a Power Stage of D.C.
Generator
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13. DC GENERATOR’S EFFICIENCIES
 Mechanical Efficiency
 Electrical Efficiency
 Overall or commercial Efficiency
 Maximum Efficiency
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14. • Mechanical Efficiency = Stage B / Stage A
= E*Ia / Mechanical input
• Electrical Efficiency = Stage C / Stage B
= Vt*IL / E*Ia
• Overall Efficiency = Stage C / Stage A
= Vt*IL / Mechanical input
• Maximum Efficiency : variable losses = constant lossesonstant
loss
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15. Thanks for being with us......
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