Some web resources The schematics shown here are idealised, to make the principles obvious.
Armature at degrees. The relationship of armature rotation and the AC output can be seen in Ac dc three phase generators 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. 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.
Armature of revolving armature single-phase generator with 4 windings and its output sine wave. Single phase generator with four poles 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 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.
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 degrees, the output voltage is alternated to produce the highest voltage on the other direction. 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.Aug 22, · The magnet’s north and south poles cause the current to flow in opposite directions, producing an alternating tranceformingnlp.com DC generators, the coil through which the current flows rotates in a fixed field.
What is the difference between an AC and a DC generator based on their construction? Three phase windings on the stator provide. The main objective of this report is to describe the investigation into operating characteristics of AC-DC Three-Phase generators and motors.
Turbine-driven generators (for short: turbogenerators) take advantage of the fact As it will be shown later, alternators operate with both alternating (ac) and direct-current (dc) electric power. The dc can be considered a particular case of the general ac, with frequency equal to zero.
THREE-PHASE CIRCUITS 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 . The traction alternator usually incorporates integral silicon diode rectifiers to provide the traction motors with up to volts DC (DC traction, which is used directly) or the common inverter bus (AC traction, which is first inverted from dc to three-phase ac).
There are two basic types of 3-phase generators (alternating-current generators): (1) the revolving-armature type (Figure 1) and (2) the revolving-field type (Figure 2).
The 3-phase revolving-armature generator rotates the three single-phase windings, located mechanical degrees apart on the rotor assembly, around the inside of a fixed or.