1. No-Load Characteristics
For series generator, armature current (Ia) = field current (If). So for no load characteristics we need to separately excited the generator. Hence, no-load characteristics are same as that of Characteristics Separately Excited Generator.
2. Load Characteristics
This is also obtained by separately exciting the generator field winding. So same characteristics as load characteristics. So, same characteristics as that of Separately Excited Generator.
The slope of line OC depends on total resistance in series circuit i.e. sum of armature circuit resistance(Ra), series field resistance(Rse) and load resistance (RL).
If total series resistance > Critical Resistance (Rcr), voltage build-up will not take place.
Curve 3 is obtained by adding (Ia r) to curve 2 where r=Ra + Rse
1. No-Load Characteristics
2. Load Characteristics
3. Internal Characteristics
3. External Characteristics
As Load Resistance is reduced, Armature Current increases and since it is same as field current also increases which leads to increase in flux and hence induced voltage also increases. Now, the terminal voltage V = Ea - Ia(Ra + Rse), increases until breakdown point is reached and after that machine enters saturation and Ⲫ becomes constant, so Ea becomes constant and due to increase in armature current terminal voltage reduces.
4. Armature Characteristics
Armature characteristics will be straight line as Field Current is same as Armature Current or Load Current.
→ The circuit shown below indicates how Series Generator is used in a line to increase the voltage or act as a booster.
Series Generator mainly used as series booster connected in the transmission line to neutralize ohmic drop.
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