Table Of Content
DC GENERATOR WORKING
A DC generator is a machine employed for converting mechanical energy to direct current (DC) electric power on the principle of electromagnetic induction. Below is a step-by-step account of the operation of a DC generator
DC GENERATOR WORKING PRINCIPLES
Working Principle of a DC Generator The technique relies on the Law of Electromagnetic Induction of Faraday, which states that if a conductor is brought into a magnetic field, it generates an EMF in the conductor.
KEY ELEMENT OF A DC GENERATOR
- Yoke (Frame)—To provide structural support and bear the flux.
2. Poles & Pole Shoes— Production of the magnetic field.
3. Field Windings— Supplied with current to produce an electromagnet.
4. Armature Core— The moving component where voltage is induced.
5. Armature Windings— EMF production occurs in conductors here.
6. Commutator— Conversion of AC to DC.
7. Brushes— Receive current from the commutator and deliver it to the external circuit.
Working Setup Of A Dc Generator
Armature Rotation :
Armature is designed to rotate as a result of an external mechanical force (e.g., turbine, engine).
Cutting of Magnetic Flux :
Armature windings are designed to cut the magnetic flux created by the field poles, hence creating an alternating EMF (AC)
Rectification by commutator:
A commutator (a circular ring cut in half) at the proper time commutates the polarity of induced EMF and results in AC-to-DC pulsating conversion.
Current Collection by Brushes :
Carbon brushes collect the converted current from the commutator and deliver it to the external load.
Output DC Voltage :
The result is a pulsating but one-way DC voltage, which may be filtered out by employing supplementary windings or filters.
Key Equations Induced EMF (E):
Where:
- P = Poles
- Ï• = Flux per pole (Weber)
- Z = Number of armature conductors
- N = Speed in RPM
- A = Number of parallel paths
Types of DC Generators :
- Separately Excited Generator—Field winding is fed from an external source.
- Self-Excited Generator—Field winding fed by the generator.
- Series Wound—Field winding in series with armature.
- Shunt Wound—Field winding in parallel with the armature.
- Compound Wound—Series and shunt windings compounded.
Applications of DC Generators
- Used in electroplating, battery charging, welding machines, and as exciters for AC generators.
- Earlier used in traction systems, but now mostly replaced by AC generators with rectifiers.
Summary
A DC generator works by rotating an armature in a magnetic field and generating an EMF. The commutator converts AC to DC, with the output being received by brushes. The developed voltage is a function of speed, flux, and machine design.