Single-phase generator
Therefore, single-phase generators are found in applications that are most often used when the loads being driven are relatively light,[1] and not connected to a three-phase distribution, for instance, portable engine-generators.
A basic design, called elementary generator,[3] is to have a rectangular loop armature to cut the lines of force between the north and south poles.
The current is sent out of the generator unit through two sets of slip rings and brushes, one of which is used for each end of the armature.
In this two-pole design, as the armature rotates one revolution, it generates one cycle of single phase alternating current (AC).
At zero degrees, the rectangular arm of the armature does not cut any lines of force, giving zero voltage output.
In one rotation, the AC output is produced with one complete cycle as represented in the sine wave.
More poles can also be added to single-phase generator to allow one rotation to produce more than one cycle of AC output.
The current is still delivered out through the two sets of slip rings and brushes in the same fashion as in the two-pole configuration.
As a result, the output voltage is increased 4 time as shown in the sine wave in the diagram.
There are two magnetic poles, north and south, attached to a rotor and two coils which are connected in series and equally spaced on stator.
[9] Even with newer three-phase motors which were introduced to some modern trains, the single-phases transmission for traction networks survive their time and are still in use in many railways today.
[11] In the early development of hydroelectricity, single-phase generators played an important role in demonstrating the benefits of alternating current.
The plant was the first to generate alternating current electric power for industrial application and it was a demonstration of the efficiency in AC transmission.
That left the applications for single-phase hydroelectricity generation to special cases such as in light loads.
An example of using single-phase in a special case was implemented in 1902 at St. Louis Municipal Electric Power Plant.
[13] The main usage of single-phase hydroelectricity generation today is to supply power for traction network for railways.
The other four are single-phase generators are connected to Pelton turbines which have combined capacity of 52 MW to supply the German 15 kV AC railway electrification.
[14] Similar single-phase hydroelectricity generations are also used in another variance of railway electrification system in the United States.
Two out of its 14 turbines are connected to two single-phase generators to supply Amtrak's 25 Hz traction power system.
An installation at St. Louis Municipal Electric Power Plant in the 1900s was an example of using steam engines with single-phase generators.
The St. Louis plant used compound steam engine to drive a 100 kW single-phase generator which produced current at rated power of 1,150 volts.
The single-phase generators were eventually retired in the late 1970s due to concerns of a turbine failure in another station.
