transformers & types of transformers

Q. Know About Different Types Of Transformers And Its Uses?

TRANSFORMER- one of the oldest innovations in Electrical Engineering. A Transformer is an electrical device that can be used to transfer the power from one circuit and another circuit without physical contact and without changing its characteristics like frequency, phase. It is an essential device in every electrical network circuitry. It consists majorly two circuits, namely primary circuit and one or more secondary circuit. Please refer the link Everything You Need to Know About Transformers & Working of Transformer. In this discussion, we deal with different types of transformers.

Working Principle of Transformer

The transformer working depends upon Faraday’s electromagnetic induction law. The mutual induction phenomenon between two or more winding is responsible for power transformation.

According to Faraday’s laws, “The Rate of change of flux linkage with respect to time is directly proportional to the EMF induced in a conductor or coil”.

E= N dϕ /dt

Where,

E = Induced EMF

N = the number of turns

dϕ = Change in flux

dt = Change in time

Types of Transformers

There are several transformer types used in the electrical power system for different purposes, like in power generation, distribution and transmission and utilization of electrical power. The transformers are classified based on voltage levels, Core medium used, winding arrangements, use and installation place, etc. Here we discuss different types of transformers are the step up and step down Transformer, Distribution Transformer, Potential Transformer, Power Transformer, 1-ϕ and 3-ϕ transformer, Auto transformer, etc.

Transformers Based on Voltage Levels
These are the most commonly used transformer types for all the applications. Depends upon the voltage ratios from primary to secondary windings, the transformers are classified as step-up and step-down transformers.

Step-Up Transformer
As the name states that, the secondary voltage is stepped up with a ratio compared to primary voltage. This can be achieved by increasing the number of windings in the secondary than the primary windings as shown in the figure. In power plant, this transformer is used as connecting transformer of the generator to the grid.

Step-Down Transformer:- It used to step down the voltage level from lower to higher level at secondary side as shown below so that it is called as a step-down transformer. The winding turns more on the primary side than the secondary .

In distribution networks, the step-down transformer is commonly used to convert the high grid voltage to low voltage that can be used for home appliances.

Transformer Based on the Core Medium Used

Based on the medium placed between the primary and secondary winding the transformers are classified as Air core and Iron core

Air Core Transformer :- Both the primary and secondary windings are wound on a non-magnetic strip where the flux linkage between primary and secondary windings is through the air.

Compared to iron core the mutual inductance is less in air core, i.e. the reluctance offered to the generated flux is high in the air medium. But the hysteresis and eddy current losses are completely eliminated in air-core type transformer.

Iron Core Transformer:- Both the primary and secondary windings are wound on multiple iron plate bunch which provide a perfect linkage path to the generated flux. It offers less reluctance to the linkage flux due to the conductive and magnetic property of the iron. These are widely used transformers in which the efficiency is high compared to the air core type transformer.

Transformers Based on Winding Arrangement

Auto Transformer

Standard transformers have primary and secondary windings placed in two different directions, but in autotransformer windings, the primary and the secondary windings are connected to each other in series both physically and magnetically as shown in the figure below.
On a single common coil which forms both primary and secondary winding in which voltage is varied according to the position of secondary tapping on the body of the coil windings.

Transformers Based on Usage
According to the necessity, these are classified as the power transformer, distribution transformer measuring transformer, and protection transformer.

Power Transformer
The power transformers are big in size. They are suitable for high voltage (greater than 33KV) power transfer applications. It used in power generation stations and Transmission substation. It has high insulation level.

Distribution Transformer
In order to distribute the power generated from the power generation plant to remote locations, these transformers are used. Basically, it is used for the distribution of electrical energy at low voltage is less than 33KV in industrial purpose and 440v-220v in domestic purpose.

some advantages of distribution transformer

1. It works at low efficiency at 50-70%
2. Small size
3. Easy installation
4. Low magnetic losses
5. It is not always fully loaded
   

3. Measurement Transformer

Used to measure the electrical quantity like voltage, current, power, etc. These are classified as potential transformers, current transformers etc.

4.Protection Transformers

This type of transformers is used in component protection purpose. The major difference between measuring transformers and protection transformers is the accuracy that means that the protection transformers should be accurate as compared to measuring transformers.