MAGNETISATION CURVE
The magnetisation curve is the relationship between air-gap flux Ø and the field winding Mmf or field winding current.
The dashed straight line, tangent to the straight line portion of magnetization curve at speed ωm , is called air-gap line.
OPERATING CHARACTERISTICS
DC Generators
No-load characteristic
Ea = f (If) with speed n = constant. This characteristic is also called saturation curve, open-circuit characteristic, magnetization curve or no-load magnetization curve.
Load characteristic
Vt = f (If) with both Ia and n constant. This characteristic is also called magnetization curve.
External characteristic
Vt = f (IL) with both If and n constant.
Armature characteristic or regulation curve
If = f (Ia) with both Vt and n constant
Remember :
Separately-Excited Generator
These generators are used when a wide range of output voltage is required.
No-load Characteristic
Load characteristic
External characteristics
Armature Characteristic or Voltage Regulation
Shunt Generators
Remember :
No-load Characteristics
Load Characteristic
External Characteristic
Armature Characteristic
Voltage Building in Shunt Generator
Failure to Build-up
No-residual Magnetism
Field Connections Reversed
High Field Circuit Resistance
Series Generator
These generators are used mainly as series boosters connected in the line, to neutralise the effect of line ohmic drop.
No load Characteristic
Load Characteristic (load magnetization curve)
External Characteristic
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