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Single-phase generator
Single-phase generator (also known as single-phase alternator) is an alternating current electrical generator that produces a single, continuously alternating voltage. Single-phase generators can be used to generate power in single-phase electric power systems. However, polyphase generators are generally used to deliver power in three-phase distribution system and the current is converted to single-phase near the single-phase loads instead. Therefore, single-phase generators are found in applications that are most often used when the loads being driven are relatively light, and not connected to a three-phase distribution, for instance, portable engine-generators. Larger single-phase generators are also used in special applications such as single-phase traction power for railway electrification systems.
The design of revolving armature generators is to have the armature part on a rotor and the magnetic field part on stator. A basic design, called elementary generator, is to have a rectangular loop armature to cut the lines of force between the north and south poles. By cutting lines of force through rotation, it produces electric current. 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). To generate an AC output, the armature is rotated at a constant speed having the number of rotations per second to match the desired frequency (in hertz) of the AC output.
The relationship of armature rotation and the AC output can be seen in this series of pictures. Due to the circular motion of the armature against the straight lines of force, a variable number of lines of force will be cut even at a constant speed of the motion. At zero degrees, the rectangular arm of the armature does not cut any lines of force, giving zero voltage output. As the armature arm rotates at a constant speed toward the 90° position, more lines are cut. The lines of force are cut at most when the armature is at the 90° position, giving out the most current on one direction. As it turns toward the 180° position, lesser number of lines of force are cut, giving out lesser voltage until it becomes zero again at the 180° position. The voltage starts to increase again as the armature heads to the opposite pole at the 270° position. Toward this position, the current is generated on the opposite direction, giving out the maximum voltage on the opposite side. The voltage decrease again as it completes the full rotation. 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. In an example on the left, the stator part is reconfigured to have 4 poles which are equally spaced. A north pole is adjacent to the two south poles. The shape of the armature at the rotor part is also changed. It is no longer a flat rectangle. The arm is bent 90 degrees. This allows one side of the armature to interact with a north pole while the other side interacts with a south pole similarly to the two-pole configuration. 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. The difference is that a cycle of AC output can be completed after a 180 degree rotation of the armature. In one rotation, the AC output will be two cycles. This increases the frequency of the output of the generator. More poles can be added to achieves higher frequency at the same rotation speed of the generator, or same frequency of output at the lower rotation speed of the generator depending on the applications.
This design also allows us to increase the output voltage by modifying the shape of the armature. We can add more rectangular loops to the armature as seen on the picture on the right. The additional loops at the armature arm are connected in series, which are actually additional windings of the same conductor wire to form a coil in rectangular shape. In this example, there are 4 windings in the coil. Since the shapes of all windings are the same, the amount of the lines of force will be cut at the same amount in the same direction at the same time in all windings. This creates in phase AC output for these 4 windings. As a result, the output voltage is increased 4 time as shown in the sine wave in the diagram.
The design of revolving field generators is to have the armature part on stator and the magnetic field part on rotor. A basic design of revolving field single-phase generator is shown on the right. 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. The windings of the two coils are in reverse direction to have the current to flow in the same direction because the two coils always interact with opposing polarities. Since poles and coils are equally spaced and the locations of the poles match to the locations of the coils, the magnetic lines of force are cut at the same amount at any degree of the rotor. As a result, the voltages induced to all windings have the same value at any given time. The voltages from both coils are "in phase" to each other. Therefore, the total output voltage is two times the voltage induced in each winding. In the figure, at the position where pole number 1 and coil number 1 meet, the generator produces the highest output voltage on one direction. As the rotor turns 180 degrees, the output voltage is alternated to produce the highest voltage on the other direction. The frequency of the AC output in this case equals to the number of rotations of the rotor per second.
This design can also allow us to increase the output frequency by adding more poles. In this example on the right, we have 4 coils connected in series on the stator and the field rotor has 4 poles. Both coils and poles are equally spaced. Each pole has opposite polarity to its neighbors which are angled at 90 degrees. Each coils also have opposite winding to its neighbors. This configuration allows the lines of force at 4 poles to be cut by 4 coils at the same amount at a given time. At each 90-degree rotation, the voltage output polarity is switched from one direction to the other. Therefore, there are 4 cycles of the AC output in one rotation. As the 4 coils are wired in series and their outputs are "in phase", the AC output of this single-phase generator will have 4 times the voltage of that generated by each individual coil.
A benefit of the revolving field design is that if the poles are permanent magnets, then there is no need to use any slip ring and brush to deliver electricity out of the generator as the coils are stationary and can be wired directly from the generator to the external loads.
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Single-phase generator AI simulator
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Single-phase generator
Single-phase generator (also known as single-phase alternator) is an alternating current electrical generator that produces a single, continuously alternating voltage. Single-phase generators can be used to generate power in single-phase electric power systems. However, polyphase generators are generally used to deliver power in three-phase distribution system and the current is converted to single-phase near the single-phase loads instead. Therefore, single-phase generators are found in applications that are most often used when the loads being driven are relatively light, and not connected to a three-phase distribution, for instance, portable engine-generators. Larger single-phase generators are also used in special applications such as single-phase traction power for railway electrification systems.
The design of revolving armature generators is to have the armature part on a rotor and the magnetic field part on stator. A basic design, called elementary generator, is to have a rectangular loop armature to cut the lines of force between the north and south poles. By cutting lines of force through rotation, it produces electric current. 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). To generate an AC output, the armature is rotated at a constant speed having the number of rotations per second to match the desired frequency (in hertz) of the AC output.
The relationship of armature rotation and the AC output can be seen in this series of pictures. Due to the circular motion of the armature against the straight lines of force, a variable number of lines of force will be cut even at a constant speed of the motion. At zero degrees, the rectangular arm of the armature does not cut any lines of force, giving zero voltage output. As the armature arm rotates at a constant speed toward the 90° position, more lines are cut. The lines of force are cut at most when the armature is at the 90° position, giving out the most current on one direction. As it turns toward the 180° position, lesser number of lines of force are cut, giving out lesser voltage until it becomes zero again at the 180° position. The voltage starts to increase again as the armature heads to the opposite pole at the 270° position. Toward this position, the current is generated on the opposite direction, giving out the maximum voltage on the opposite side. The voltage decrease again as it completes the full rotation. 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. In an example on the left, the stator part is reconfigured to have 4 poles which are equally spaced. A north pole is adjacent to the two south poles. The shape of the armature at the rotor part is also changed. It is no longer a flat rectangle. The arm is bent 90 degrees. This allows one side of the armature to interact with a north pole while the other side interacts with a south pole similarly to the two-pole configuration. 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. The difference is that a cycle of AC output can be completed after a 180 degree rotation of the armature. In one rotation, the AC output will be two cycles. This increases the frequency of the output of the generator. More poles can be added to achieves higher frequency at the same rotation speed of the generator, or same frequency of output at the lower rotation speed of the generator depending on the applications.
This design also allows us to increase the output voltage by modifying the shape of the armature. We can add more rectangular loops to the armature as seen on the picture on the right. The additional loops at the armature arm are connected in series, which are actually additional windings of the same conductor wire to form a coil in rectangular shape. In this example, there are 4 windings in the coil. Since the shapes of all windings are the same, the amount of the lines of force will be cut at the same amount in the same direction at the same time in all windings. This creates in phase AC output for these 4 windings. As a result, the output voltage is increased 4 time as shown in the sine wave in the diagram.
The design of revolving field generators is to have the armature part on stator and the magnetic field part on rotor. A basic design of revolving field single-phase generator is shown on the right. 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. The windings of the two coils are in reverse direction to have the current to flow in the same direction because the two coils always interact with opposing polarities. Since poles and coils are equally spaced and the locations of the poles match to the locations of the coils, the magnetic lines of force are cut at the same amount at any degree of the rotor. As a result, the voltages induced to all windings have the same value at any given time. The voltages from both coils are "in phase" to each other. Therefore, the total output voltage is two times the voltage induced in each winding. In the figure, at the position where pole number 1 and coil number 1 meet, the generator produces the highest output voltage on one direction. As the rotor turns 180 degrees, the output voltage is alternated to produce the highest voltage on the other direction. The frequency of the AC output in this case equals to the number of rotations of the rotor per second.
This design can also allow us to increase the output frequency by adding more poles. In this example on the right, we have 4 coils connected in series on the stator and the field rotor has 4 poles. Both coils and poles are equally spaced. Each pole has opposite polarity to its neighbors which are angled at 90 degrees. Each coils also have opposite winding to its neighbors. This configuration allows the lines of force at 4 poles to be cut by 4 coils at the same amount at a given time. At each 90-degree rotation, the voltage output polarity is switched from one direction to the other. Therefore, there are 4 cycles of the AC output in one rotation. As the 4 coils are wired in series and their outputs are "in phase", the AC output of this single-phase generator will have 4 times the voltage of that generated by each individual coil.
A benefit of the revolving field design is that if the poles are permanent magnets, then there is no need to use any slip ring and brush to deliver electricity out of the generator as the coils are stationary and can be wired directly from the generator to the external loads.