13 May, 2023

All you need to know about electrical transformers!

Electrical transformers, their types and components 

Electrical transformers are considered one of the important electrical and electronic components that are used in many different applications in order to raise or lower the voltage and electric current.

The need to use electrical transformers in generating stations to raise voltages for specific values has begun because of the need to transfer power for less loss and costs and to reduce the size of connectors in the grid which is used to feed electric loads with suitable voltages.

What is the electrical transformer?

Transformer is defined as a static electrical machine (non-moving) whose function is to convert an alternating current of a certain voltage into another alternating current of a different voltage, either by rise or fall with constant capacity and frequency, and the electrical transformer is used to transfer electrical energy from the places of its generation to the places of consumption.

Electrical transformer components

  • Iron heart:

It is a set of thin sheets of magnetic iron, the thickness of which ranges from (0.35 mm) to (0.5 mm), and they are isolated from each other to overcome the phenomenon of eddy currents.

  • Copper coils: consisting of:
  • Primary coils: It is a coiled and insulated copper wire, and is connected directly to the electrical source.
  • Secondary coils: A coiled and insulated copper wire that connects the electrical load or to the bridge circuit.

The working principle of an electric transformer:

When the primary coil of the transformer is connected to the electrical source, the alternating current passes through a magnetic flux component that cuts the secondary coil through the magnetic circuit consisting of the iron core.

Note: The amount of driving force in electrical transformers depends mainly on the number of turns in each coil.

Types of electrical transformers:

Classification of electrical transformers according to the shape of the iron core:

  • Core form: In this type of transformer, the iron core is made of steel strips in the form of a rectangle, and the primary and secondary coils are placed on both ends of the iron core, as shown in the following picture.
  • Shell form: The iron core in this type of transformer consists of steel strips in the form of three legs. The coils are placed on the central leg so that they are isolated from each other as shown in the following picture.

Classification of electrical transformers in terms of voltage level:

  • Power transformers: They are the transformers that are used in electric power transmission networks (above 33kv), such as 400kv/132kv transformers and 132kv/33kv transformers.
  • Distribution transformer: These are the transformers used in electrical power distribution networks (up to 33kv), such as 33kv/11kv, and 33kv/0.4kv.

Classification of electrical transformers according to the number of phases:

  • Single phase transformer: It consists of one primary coil and one secondary coil.
  • Three-phase transformer: It consists of three primary coils and three secondary coils.

The difference between transformers, generators and motors

Although the term Electric Machine always applies to generators and motors of all kinds, the transformer is also considered a type of electrical machine, because the laws governing the work of motors, generators, and transformers are the same, which are the laws of electromagnetism.

The only difference between motors and generators on the one hand, and between transformers on the other hand, is that motors and generators depend on the principle of motion (rotating), while transformers are static electrical machines that do not rotate. Other than that, they are all subject to the laws of electromagnetism.

Electrical Transformer uses

  1. generating stations.
  2. transport networks.
  3. distribution networks.
  4. To feed electrical appliances.
  5. Networks of large and medium factories.
  6. electronic boards.

Advantages of using electrical transformers

The main advantage of transformers in the electric power system is to reduce the value of the current transmitted through lines and cables, and this feature entails several other advantages:

  • Reducing the power lost during the transmission of electrical energy.
  • Reduce the value of the drop in voltage.
  • Reducing the cost of transmission lines and electric power towers.

The importance of electrical transformers

The importance of electrical transformers mainly lies in converting the electric power that enters it with a certain voltage into an electric power that comes out of it with a different voltage, whether by increase or decrease.

The electric transformer is used as a main component in the transmission lines in order to transmit electrical energy with high voltages over long distances with the least possible losses in energy.

Ways to connect three-phase transformers:

Three phase circuits can be connected in different ways, including:

  • The delta connection – Δ method, by connecting the end of each file to the beginning of the file next to it.
  • Star connection – Y method by connecting all ends of the coils together. 

Since the transformers consist of two primary and secondary circuits, each circuit can be connected in a delta or star manner. This means that there are four ways to connect three-phase transformers, namely:

  • Y-Y transformer: In this method, the primary and secondary coils are connected in the form of a star.
  • Δ- Δ transformer: Both primary and secondary windings are connected in delta way
  • Y- Δ transformer: The primary coils are connected by the star method, while the secondary coils are connected by the delta method
  • Δ-Y transformer: The primary coils are connected in a delta manner and the secondary coils are connected in a star manner

Why is the power of electrical transformers measured in volt.ampere and not in watts?

The capacity of transformers is measured in volts.ampere for two reasons:

  • Electrical loads are constantly changing, as changing electrical loads leads to a change in the power factor, which in turn changes the real power, which is measured in watts.
  • There are two types of losses, the first is the copper losses that depend on current, and the other is the iron losses that depend on voltage.

Atlas for Support and Services has distinguished practical experiences in inspection, preparation and testing services for electrical transformers, starting from the manufacturing stage of the electric transformer and ending with installation and maintenance through a team of highly experienced engineers and technicians using the latest testing equipment and various tests. In addition, Atlas grants quality and safety certificates for the various electrical transformers and accreditation certificates International standards for electrical transformers such as ISO / IEC.

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