DC shunt generators are a common type of generator, most often functioning as battery chargers or exciters for other generators. They are named for the way in which their field winding is connected to the generator's armature. A generator's winding is the coil which generates the magnetic field that motivates the generator. In a DC shunt generator, the winding is situated parallel to the armature, or spinning element, of the generator.
The defining characteristic of a DC shunt generator is how its winding is oriented. DC shunt generators have a field winding situated parallel with the armature of the generator. This causes the voltage to be applied directly across the field circuit, which in turn means that additional flux is created and the total voltage output is increased.
The excitation current of a DC shunt generator is decided by the output voltage and the field resistance of the generator. In most DC shunt generators the excitation is kept at about 0.5 per cent to 5 per cent of the generator's overall electrical output.
Voltage Output Behavior
In this type of generator, the voltage output is very stable as long as the generator works within its defined parameters. However, as the load current gets closer to the generator's full load rating, the voltage output begins to decrease more sharply.
Critical External Resistance
Load current and load resistance are inversely proportional up to a certain point. When load resistance decreases, load current increases. However, every DC shunt generator has a point where load resistance stops decreasing. Rather than further increasing the current, the halting of load resistance instead decreases it. Therefore, load resistance cannot be decreased too far or the generator will cease to excite.