AC Generator: Working Principles, Parts, Applications

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ac electric generators

Electricity has become one of the essential needs in our daily needs along with Roti, Kapda, Makan and Education. Without electricity or alternating currents in batteries, we cannot think of switching our fans in scorching heat to using a heater or electric kettle in extreme cold. But all these machine operates on a fundamental principle of physics which is known as electromagnetic induction. In essence, electromagnetic induction dictates that a voltage, or electromotive force (EMF), is induced in a conductor whenever there is relative motion between a magnetic field and the conductor. In this blog, let us understand what is ac electric generators, their parts and working principles, advantages, uses, etc.

What is an AC Generator?

An AC generator is an electromechanical device which converts mechanical energy into electrical energy in the form of an alternating current (AC). This workhorse machine operates on a fundamental principle of physics known as Farraday’s law of electromagnetic induction. This principle states that whenever a conductor moves through a magnetic field, an electric current is induced within the conductor.

Credits: Pinterest

Parts of AC Generators

The different parts of AC Generators are – 

  • Stator
  • Rotor
  • Rotor Windings
  • Field
  • Prime Mover
  • Slip Rings

Let us understand the functions of these parts of the ac electric generators – 

  • Stator: The stator consists of a hollow cylindrical frame which is made of steel and has a magnetic field system. This system can involve electromagnets which are created by coils of wire wrapped around iron cores or permanent magnets, placed within the frame. This is a stationary component and is used to reduce eddy current losses. 
  • Rotor: The rotor is also known as the armature, it is the rotating component of the generator. It consists of a cylindrical core made of laminated steel to minimize energy losses due to eddy currents. Embedded within the core are slots that have the rotor conductors, they are coopper windings arranged in a specific configuration.
  • Rotor Windings: The rotor windings are the current-carrying elements within the rotor. These coils of wire are meticulously arranged and connected in a specific configuration to maximize the induced voltage. The configuration can be single-phase or three-phase, depending on the desired output characteristics.
  • Prime Mover: The prime mover is the external source of mechanical energy that drives the rotation of the rotor. Depending on the specific application and available resources, this prime mover can be a steam turbine, gas turbine, water turbine or internal combustion engine. The prime mover’s role is to keep the rotor spinning consistently within the stator’s magnetic field.
ac electric generator
Credits: Pinterest
  • Slip Rings: Slip rings are employed in some AC generator designs, particularly those with rotating field windings. These are specialised electrical connectors that rotate with the rotor shaft. Brushes that are made of conductive material, make contact with the slip rings, letting the transfer of electrical current between the rotating rotor windings and the stationary external circuit.
  • Field: The field refers to the magnetic field system placed within the stator. This system, as mentioned earlier, can be comprised of electromagnets or permanent magnets. The field’s primary function is to establish a steady and strong magnetic field within the generator. This magnetic field interacts with the rotor windings to induce an electric current.

By working together, these components transform mechanical energy from the prime mover into the alternating current that gives power to our homes, industries and countless applications.

Also Read – Balanced Force: Definition, Example and Characteristics

Types of AC Generators

An AC electric generator can be divided into two parts  depending on the number of phases – 

  1. Single-Phase AC Generators: These generators produce single alternating current waveform. They are usually used in smaller applications or for powering individual devices.
  2. Three-Phase AC Generators: These generators produce three separate AC waveforms, each of them with a slight difference between them. This three-phase system is the pillar of modern power grids due to its efficiency in transmitting and distributing electrical power over long distances. 

The specific type of generator depends on the use of the power requirement and configuration of the AC current output.

Working principle of AC Generators

The alternating current (AC) generator operates on the well-established principle of electromagnetic induction. Here is how an AC generator works – 

  • Inside these generators, a strong magnetic field is created by magnets or electromagnets.
  • As the rotor windings spin within the magnetic field, they constantly cut through it. This back-and-forth movement creates a voltage, or “push,” in the wires. This voltage keeps changing direction as the windings move through the field.
  • The changing voltage creates an alternating current in the wires. This means the current constantly switches direction, unlike the steady flow in a battery.
  • The generated current is then sent out of the generator through wires to power our homes and appliances.

In simpler terms, the AC generator uses the movement of wires through a magnetic field to create a constantly changing voltage, resulting in alternating current. This is the type of electricity that powers most of our modern world.

Also Read – What is the Difference Between Current and Static Electricity?

Advantages of AC Generators

The advantages of these generators are – 

  1. They can be used with transformers to easily increase (step up) or decrease (step down) the voltage of electricity.
  2. AC generators experience less energy loss during transmission, making them safe for use at homes and buildings.
  3. They have a simpler design as compared to DC generators, making them easier to manufacture and maintain
  4. These generators produce the same type of electricity (AC) used by most motors in our homes and industries.
  5. These generators are versatile and can be powered by various sources like steam turbines, wind turbines and water turbines, making them usable in various set-ups to generate electricity.
Credits: Pinterest

Application of AC Generators

The application of AC generators in our day-to-day life is – 

  1. AC generators at power plants, powered by sources like coal, wind or water, create the electricity that flows through power lines to our homes for our normal use.
  2. The AC current from generators charges the batteries in our laptops, phones and other devices.
  3. These generators are used in wind turbines, converting wind energy into the electricity used for powering our houses.
  4. Large generators supply the electricity that runs powerful electric motors in factories and industrial settings.
  5. Even the small generators in car alternators use the same principles as large power plant generators to keep our car batteries charged.


What is the principle of AC and DC generators?

In an alternating current (AC) generator, the current flows in a specific direction on a regular basis. In a direct current (DC) generator, the electric current flows in a single direction only. In AC generators, the current coil is stationary while the magnet is moving. The design is straightforward and the cost is low.

What are the applications of AC generators?

AC generators can be used in a variety of applications including bicycles, electric scooters, microwaves, and sailboats, to generate AC current. The mechanical energy required to power these generators is provided by steam and gas turbines, as well as internal combustion engines.

What uses an AC generator?

The main difference between an AC and a DC generator is the size of the generator. An AC generator can be used to power small electrical appliances in your business – like coffee machines and computers – while a DC generator can power large electric motors, like those used in metro systems.

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Hope this blog helps you understand ac electric generators. Keep reading more of our blogs to learn about the basic concepts of Physics!

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