What is an Oscillator?
Principle of DC Generator
Construction of DC Generator | Yoke Pole Armature Brushes of DC Generator
Characteristics of Series Wound DC Generator
Characteristic of Separately Excited DC Generator
EMF Equation of DC Generator
Parallel Operation of DC Generators
Self Excited DC Generators
Phasor Diagram for Synchronous Generator
DC Generators Performance Curves
Types of DC Generators
Characteristic of Shunt Wound DC Generator
Magnetization Curve of DC Generator
Applications of DC Generators
Alternator Synchronous Generator | Definition and Types of Alternator
Working Principle of Alternator
Construction of Alternator
Armature Reaction in Alternator or Synchronous Generator
Armature Winding of Alternator
Rating of Alternator
Derivation of Various Power Conditions in Alternators and Synchronous Motors
Induction Generator | Application of Induction Generator
Motor Generator Set | M G set
Armature Winding | Pole Pitch Coil Span Commutator Pitch
Winding Factor | Pitch Factor | Distribution Factor
Frog Leg Winding | Drum Winding | Gramme Ring Winding
Types of DC Generators
- Field coils excited by permanent magnets – Permanent magnet DC generators.
- Field coils excited by some external source – Separately excited DC generators.
- Field coils excited by the generator itself – Self excited DC generators.
Permanent Magnet DC GeneratorWhen the flux in the magnetic circuit is established by the help of permanent magnets then it is known as Permanent magnet DC generator.
It consists of an armature and one or several permanent magnets situated around the armature. This type of dc generators generates very low power. So, they are rarely found in industrial applications. They are normally used in small applications like dynamos in motor cycles.
Separately Excited DC GeneratorThese are the generators whose field magnets are energized by some external dc source such as battery .
A circuit diagram of separately excited DC generator is shown in figure. Ia = Armature current IL = Load current V = Terminal voltage Eg = Generated emf Voltage drop in the armature = Ia × Ra (R/sub>a is the armature resistance) Let, Ia = IL = I (say) Then, voltage across the load, V = IRa Power generated, Pg = Eg×I Power delivered to the external load, PL = V×I.
Self-excited DC GeneratorsThese are the generators whose field magnets are energized by the current supplied by themselves. In these type of machines field coils are internally connected with the armature. Due to residual magnetism some flux is always present in the poles. When the armature is rotated some emf is induced. Hence some induced current is produced. This small current flows through the field coil as well as the load and thereby strengthening the pole flux. As the pole flux strengthened, it will produce more armature emf, which cause further increase of current through the field. This increased field current further raises armature emf and this cumulative phenomenon continues until the excitation reaches to the rated value. According to the position of the field coils the Self-excited DC generators may be classified as…
- Series wound generators
- Shunt wound generators
- Compound wound generators