DC Generators Principle of Generator Action Types of DC Generators Separately Excited Self Excited Voltage Regulation Power and Efficiency Power Stages Losses in DC Generators Efficiency
Principle of Generator Action Requirements for Generator Action or Generating Voltage Presence of magnetic lines of force Motion of conductors cutting the flux When a conductor moves at constant speed across a uniformly dense magnetic field, voltage is generated in the conductor. 1 volt is generated for every 100,000,000 lines cut per second
Principle of Generator Action Commutation
Principle of Generator Action Average Voltage of a Generator If the magnetic field is not uniform, the generated voltage can be defined by its average value as defined by 𝐸 ??? = Ø ? × 10 −8 ????? Where 𝐸 ??? Average generated voltage per conductor Volts Ø Total flux cut by the conductor Maxwells ? Time during cutting took place Seconds
Principle of Generator Action General Voltage Equation 𝐸 ? = 𝑃 × 𝑧 × ??? × Ø × 10 −8 60 × 𝜕 Where 𝐸 ? Generated voltage Volts 𝑃 Number of poles Unitless 𝑧 Number of armature conductors Unitless ??? Speed of the armature Rev per min Ø Flux per pole Maxwells 𝜕 Number of parallel paths Unitless
Principle of Generator Action General Voltage Equation For Lap Winding 𝜕 = ?𝑃 Where ? = 1 for simplex winding ? = 2 for duplex winding 𝜕 Number of armature paths Unitless ? Multiplicity factor Unitless 𝑃 Number of poles Unitless
Principle of Generator Action General Voltage Equation For Wave Winding 𝜕 = 2? Where ? = 1 for simplex winding ? = 2 for duplex winding 𝜕 Number of armature paths Unitless ? Multiplicity factor Unitless
Types of DC Generators
Types of DC Generators Separately Excited Field windings are energized by an external DC source. The generated voltage is purely dependent on the amount of current passing through the field windings.
Types of DC Generators Equivalent Circuit of a Separately Excited Generator 𝑉 𝐿 = 𝐸 ? − 𝐼 ? ? ? + ? ? − 𝑉 ? 𝐼 ? = 𝐸 ? ? Where 𝑉 𝐿 Voltage across the load Volts 𝐸 ? Generated voltage Volts 𝐼 ? Exciting current Amperes ? ? Field winding resistance Ohms
Types of DC Generators Equivalent Circuit of a Separately Excited Generator 𝐼 ? ∝ Ø ? Where 𝐼 ? Exciting current Amperes Ø ? Field flux Maxwells
Types of DC Generators Self Excited Field windings are energized by the output of the generator itself.
Types of DC Generators Shunt Generator A generator whose field windings (shunt winding) are connected across or in parallel with the armature conductors and the brushes.
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- Magnetic Field, DC GENERATORS