There are three distinct varieties of direct current (DC) generators: series-wound, shunt-wound, and compound-wound. The connection of the field windings to the outside circuit distinguishes the various designs.
Series-Wound DC Generators
The term “series-wound DC generator” refers to a type of generator in which the field windings are connected to the armature and the external circuit in a series configuration (load). Look at the example in Figure 1.
Because the load current flows through the field windings, a series-wound generator has only a few turns of low-resistance wire in them.
This is known as the generator’s voltage regulation, and it refers to the generator’s capacity to maintain a constant voltage output regardless of changes in the load. The voltage regulation in series-wound generators is subpar. Voltage regulation is a problem with series-wound DC generators, so they are rarely used.
To adjust the voltage produced by a series-wound generator, a rheostat (variable resistor) is wired in parallel with the field windings.
Shunt-Wound DC Generators
DC generators with their field windings connected in parallel (shunt) with the armature and the external circuit are known as shunt-wound generators (load). For more information, please refer to Figure 2.
The output is reduced because current flowing through the field windings is not used. High-resistance wire is wound tightly into many turns in the field windings to limit the amount of current that can flow through them.
If the load is constant, a shunt-wound generator is the best option. But if the load changes, so does the voltage. A rheostat connected in series with the shunt field allows for regulation of the generator’s output voltage when using a shunt winding.
Compound-Wound DC Generators
A DC generator with both series and shunt field windings is known as a compound-wound generator. It is possible to combine the benefits of series field windings and shunt field windings in a compound-wound generator.
In most cases, the shunt field will be more powerful. In this case, the series field is only employed to counteract factors that would otherwise reduce the output voltage. View Figure 3.