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All you need to know about Generators

The output power is then taken from the stationary windings. That output power is further connected to the fixed terminals. These number of windings help out in the production of large currents. You can handle a large amount of current because there is no sliding contact of the rings.
3-phase AC Generators

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AC electrical generators are often used in households and industries today. Their presence in some homes and industrial warehouses speaks volumes about their utility. Following are the typical types of AC generators that are often utilized. They all perform the same function of providing electric current.

1.    Rotating Armature Generator

As the name implies, the rotor acts as the armature in this generator. It rotates while the stator provides a stationary electromagnetic field (Mason, 2019). The other details are pretty much the same. The rotor cuts the magnetic field lines. This change in flux creates the electrical current in the form of the output voltage.

From this mechanism, the slip rings and carbon brushes extract the output voltage. The rotating loop comes with attached slip rings. The carbon brushes touch the slip rings by making a sliding electrical contact. The voltage is then transferred from the slip rings to the external circuit. The mechanism of the external course is to make direct contact with the slip rings.

Applications of A Rotating Armature Generator:

When we need a small amount of power of a generator, we prefer a rotating armature generator. We have to build slips, rings, and carbon brushes when we need a large amount of current from a generator. It’s challenging and expensive to do. So, most large AC generators are rotating field generators.

2.    Rotating Field Generator

In a rotating field generator, the rotor makes way for direct current to pass. The rotor has windings in it, The direct current introduces with the help of slip rings and carbon brushes. This results in the rotating magnetic field (Ramen, 2011). While the polarity remains fixed in this case.

The phenomenon of polarity in a rotating field generator is the same as a rotating bar magnet. The magnetic field of the rotor that is rotating cuts through the stator. The stator comes with embedded armature windings. This results in the induction of alternating voltage in the windings. The reason is that at first, the magnetic fields of the first one polarity cuts. Then the other ones create the flux through them.

The output power is then taken from the stationary windings. That output power is further connected to the fixed terminals. These number of windings help out in the production of large currents. You can handle a large amount of current because there is no sliding contact of the rings. Likewise, the whole output structure is completely insulated.

Slip rings and brushes adequate for the DC field supply. The current level in the field is much smaller than in the armature circuit.

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Applications of rotating field generator:

We prefer a rotating field generator when we need a large amount of power of a generator. That’s why the rotating field AC generator is the most used generator in the market.

3.    Polyphase Generator

In its simple construction, a polyphase generator is a three-phase generator. It has two-poles in it. Each of the coils of the three-phase generator produces a sine wave. We build more coils in the stator around the rotor.

This construction produces three-phase AC power. Inside the stator, the coils place at 120o (Osman, 2017). The armature coils come with windings. And this results in the production of three different voltages for the output of three sine waves is at small breaks of time. Due to their placements, they differ in their phase by 120o.



Figure 1: A simplified three-phase AC generator

Suppose there are three waves A, B, and C. If wave A takes X time to start. Then wave B takes one-third lapse of time to generate after wave A. Likewise. Wave C takes the lapse time of two-thirds from the Wave A cycle. In simple words,

Wave A = X time

Wave B = 1/3rd of X time

Wave C = 2/3rd of X time

This is possible by the arrangement of the coils in the stator. The collection of wave production results in that:

When the voltage produced due to wave A reaches its positive peak value and returns to zero. The voltage produced due to wave B comes to its peak negative value. After that, it returns to zero.


Figure 2: A sample output voltage of a three-phase generator

The voltage in phase C has passed zero, and a negative voltage is being induced in the coil. This results in zero voltage induced during a three-phase voltage cycle.

In conclusion,

Wave A = Reaching positive peak value, starts returning to zero.

Wave B = Reaches peak negative value. After that, it starts returning to zero.

Wave C = Just passed zero voltage and moved towards pessimistic induction of voltage.

Applications of Polyphase Generator:

Most electric power generated and distributed in the stations is three-phase. This is due to the following reasons:

  • The full cost of transmission is less than for the same voltage and power in a single-phase system.
  • A three-phase generator has a 180% greater capacity than a single-phase generator. Even if the same size.
  • Single-phase voltage and power are available from a three-phase system. You can do this by using any two of the power leads from the generator.

4.    Air-cooled Generator

Two configurations apply in an air-cooled generator:

  1. Open Ventilated (OV)
  2. Enclosed Water to Air Cooled (TEWAC).

In an open ventilated design, the outdoor air use to cool the generator after it gets heated from working. Through a system of filters, the air enters the generator, cools down it. And then gets discharged outside. While in the TEWAC design, as the name implies. The water to air heat exchangers used for cooling the generator.

Also, in some restructured designs, steam turbine and other gas turbine applications use too. Its construction is like the other generators. It also has two main components, like a rotor and a stator. The generator requires a DC source to magnetize the rotor. This current source is called exciter. Depending on its design as OV and TEWAC, the components vary in several subsystems. 

The standard components are: 

  • Armature: The armature supports the iron core and windings. It consists of a steel plate called a wrapper to cover the frame.
  • Collector rings: The collector rings provide at the generator end of the rotor.

All these components are arranged in such a way to operate as independent parts. This helps process the functioning of the generator.

A facility makes inside the generator to regulate the flow of air to maintain the generator’s cool.

Applications of Air-cooled Generator:

Air-cooled generators can adjust under 30Hp engines within their construction. We can use them to generate more power. They are often used in households, small shops, and restaurants. They are resistant to varying environmental conditions.

Also, pumping Stations and Irrigation operations prefer using air-cooled generators. Because they are optimal in functioning for seldom-used septic or wastewater systems.

Conclusion:

There are many types of generators globally. However, only regular ones could be used in our life. With the improvement, they are continually upgrading to us. It’s believed that there will be a better one coming out in the future. Comment below if you have any queries about the article.

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Hey all, I'm Baymax Yan, working at a generator manufacturer and Having more than 15 years of experience in this field, and I belives that “learn and lives.” The sure thing is that I can often help my work. So I have created the blog to share all my knowledge with you. Hope my sharing helps!

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  1. Hi there, sorry for that. I have no idea about the captcha plugin on the blog platform. And I’m using original WordPress Comment. Maybe you could try Google. Thanks!

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