Electrical

Basic Concept of DC Generator and Types of DC generator

What is generator?

Generators are the energy conversion device which is used to convert mechanical energy into electrical energy. Fundamentally, two types of generators are available in the world. One is Alternating Current (AC) generator and Direct Current (DC) generator. AC generator is called alternator which means alternating generator and DC generator is called generator. In this we are going to see about the DC generator Working Principle.

Working Principle:

Generator Works under Faraday law of electromagnetic induction “the momentary conductor kept in a magnetic field the electromotive force induced in the conductor. The direction of current can be known from Fleming Right hand rules.
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Concept of DC generator:

The fundamental generation is AC voltage, but in DC generator the commutator section is converting Alternating AC Voltage to Direct current Voltage. Here carbon brushes take output from the generator to the field load circuit.

Learn More: Why Slip ring Induction motor is preferred for High starting Torque application

Also see:

Difference between Voltage and EMF
What is Voltage Drop Allowable Limit and Calculation
Fleming Left Hand Rule- Easy Remembering Tips

DC generator parts:

DC generator consist of armature winding, field winding, carbon brushes, commutator etc…..

What is armature winding:

Armature is an arrangement of conductor designed to induce the emfs by relative motion in a heteropolar magnetic field. The bunch of conductors are distributed in slots over periphery of the armature and the conductors are connected in series or parallel to form an armature winding. Armature consist of conductor, slot, coil, insulation, coil side etc.
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Closed winding: there is a closed path around the armature. DC machines are wound in closed winding structure. Closed winding are adopted for interconnection to commutator.

Note: Open windings structure uses in AC machine, closed winding structure uses in DC Machine.

Field winding:

Field winding is an electromagnetic coil which produce electromagnetic flux when the current flow through the coil. In Some small type of DC machine, the field windings are not used. Instant of field winding the permanent magnet are used to generate flux.

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Example: feedback generator, Taco generator, home appliance such as small DC motor etc.

Commutator:

Commutator is used to short the armature winding to create closed path. It is a cylindrical structure made up of copper segments stacked together, but insulated from each other by mica. The commutator is an only part differentiate AC machine and DC machine. The Main function of commutator is converting alternating current (AC) voltage in to direct current voltage. In DC generator concern the commutator is to commute or relay the generating current in the armature winding to the output circuits housed over a rotating structure through the brushes of DC generator.

Carbon Brushes:

Carbon brushes are the graphite bar and use to make a solid connection over commutator to connect the DC machine with other electrical circuits. Here the commutator and carbon brushes are used to connect the DC generator with other electrical circuit.

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Types of DC generator:

The DC generators are classified according to the types of excitation to the armature winding:

Self-Excited DC generator
Separately excited DC generator
PMMDC => permanent magnet DC generator

Self-Excited DC generator:

The field coil is directly connected with the armature winding either series-parallel or individual. The self-excited DC generator classified in to three types…

Series generator => field winding is connected in series with the armature winding
Shunt generator => Field winding is connected in parallel with the armature winding
Compound generator => field coils are connected in series and parallel with the armature winding.
- Long shunt
- Short shunt

Separately Excited generator:

For The filed winding, the power will be given through another sources. The field winding does not interfere with armature winding. This types of generator are used to regulate output power of the generator.

Also see: Why Earthing Transformer is used