various parts of transformer are: Laminated core Windings Insulating material Tank Terminals and bushings Transformer oil Tap changer Buchholz relay
A transformer is the most important electrical machine used to transfer electrical energy from one circuit to another without changing its frequency. It is used either to step up or step down the voltage to minimize transmission losses in the electrical circuits. It works on the principle of electromagnetic induction.
The main function of Transformer is to increase (step up) or decrease (step down) the voltage level of AC electrical power without changing its frequency.
Since it is a static electrical device so due to the absence of rotating parts, it has very high efficiency ( more than 95% ).
The basic parts
of transformer are its core, primary and secondary windings. Apart
from these, there are many different types of equipment installed in transformers that
are also considered as parts of transformer, such as its cooling arrangements,
protection relay ( Buchholz relay ), HT and LT terminals and bushings,
breather, conservator, oil tank, explosion vent, tap changer, etc. So let’s
discuss all these different parts of transformer and their functions in
detail.
Parts of transformer and their functions
Following are the various parts of transformer:
- Laminated core
- Windings
- Insulating material
- Tank
- Terminals and bushings
- Transformer oil
- Tap changer
- Buchholz relay
- Oil conservator
- Explosion vent
- Breather
- Radiator and fans
From all the above listed parts of transformer, laminated
soft iron core, windings, and insulating material are the basic parts of
transformer. These three are available in all types of transformers. Whereas
rest of all these parts of transformer can be seen generally in power transformer of
rating more than 100 kVA. So let's discuss each part of transformer one by one
in detail and their functions.
Laminated core
Laminated core is the most important parts of transformer, used to support the windings
of transformer. It is made up of laminated soft iron material to reduce eddy
current loss and hysteresis loss. Nowadays in the core of transformer laminated
sheets are used to minimize eddy current losses and CRGO steel material is used
to minimize hysteresis losses. The composition of core material depends on the
voltage, current, and frequency of supply to the transformer.
Have a Look:
The
diameter of transformer core becomes directly proportional to copper losses and
inversely proportional to iron losses or core losses.
Laminated
core also provides a low reluctance path for the magnetic flux that minimize leakage
flux and maximize the strength of main working flux for transformer.
Windings
In a transformer always two sets of windings are placed on laminated core and these are insulated from each other. Winding consists of several no of turns of copper conductors that is bundled together and connected in series.
 |
| windings of transformer |
The main
function of windings is to carry current and produce working magnetic flux and
induce mutual EMF for transformer action.
Windings are classified in two ways:
- Based on the input and output of supply
- Based on the voltage level of supply
Based on the input and output of the supply, windings are further classified as:
1. Primary
winding:- the
winding at which the input supply is connected is known as the primary winding.
2. Secondary
winding:- the
winding from which output is taken to the load is known as the secondary winding.
Whereas based on the voltage level of supply, windings are further classified as:
1. High voltage (HV) winding:- the winding that is connected with higher voltage is known as high voltage winding. It is made up of a thin copper conductor with a large no of turns. It can be either primary or secondary winding of the transformer.
2. Low voltage (HV) winding:- the winding that is connected with lower voltage is known as low voltage winding. It is made up of a thick copper conductor with few no. of turns. It can also be either primary or secondary winding of the transformer.
Hence
input and output to the transformer can be connected either on LV-winding or
HV-winding as per requirement.
Why transformer windings are made up of copper?
Transformer and all other electrical machines windings are made by good quality copper material due to these properties of copper.
1. Copper is a good conductor of electricity due to its higher conductivity as compared to
other materials. So this minimises the power losses in the windings.
Insulating material
Since insulation failure can cause the most severe damages to the transformer. So insulation and insulating material should be high grade and it is the most important part of transformer. Insulation is required between each turn of windings, between windings, winding and core, and all current-carrying parts and tank of transformer.
[ ##eye## Current Transformer interview
questions]
The main
function of insulating material is to protect transformer against short circuits by
providing insulation to windings so that it does not come in contact with the core
and any other conducting material.
Insulating
material of transformer should have high dielectric Properties and also good
mechanical strength and temperature withstand capability.
Synthetic
material, papers, and cotton cloth, etc are used as insulating material in
transformer.
Main Tank
Main tank is the robust part of transformer that serves mainly two purposes:
1. It protects core and windings from the external environment and provide housing for
them.
2. It
is used as a container for transformer oil and provides support for all other
external accessories of the transformer.
 |
| The main tank of the transformer |
Tanks are made up of fabricated rolled steel plates. They are provided with lifting hooks and inbuilt cooling tubes. In order to minimize the weight and stray losses, aluminum sheets are also being used instead of Steel plates. However, due to its light weight property, now-a-days aluminum tank is more familiar and costly than a steel tank.
Terminals and bushings
Terminals and bushings are also important parts of the transformer that are used to connecting incoming and outgoing cables of supply and load. These are connected with the ends of the windings conductor.
 |
| bushings of transformer |
Bushings
are mainly an insulators made up of porcelain or epoxy resins. They are mounted over the
tank and forms a barrier between terminals and tank. They provide safe passage
for the conductor connecting terminals to the windings.
As
windings are of two types and so bushings are also of two types as named below:
1.
High-voltage
bushing
2.
Low-voltage
bushing
Transformer oil
The function of transformer oil is to provide insulation between windings as well as cooling due to its chemical properties and very good dielectric strength.
[ ##eye## Core balance Current Transformer (CBCT)]
It dissipates the heat generated by the core and windings of a transformer to the external environment. When the windings of transformer gets heated due to flow of current and losses, the oil cools down the windings by circulating inside the transformer and transfer heat to the external environment through its cooling tubes.
Hydro-carbon mineral oil is used as transformer oil and acts as coolant. It is composed of
aromatics, paraffin, naphthenes, and olefins.
Tap changer
1. On-load tap changer:-
in an on-load tap changer, tapping can be changed without isolating the transformer
from the supply. Hence it is capable to operate without interrupting the power supply.
2. Off-load
tap changer:-
in off-load tap changer, the transformer needs to isolate from supply to change its
tapping (turns ratio).
An automatic tap changer is also
available.
Buchholz relay
Buchholz relay is the most important part of a power transformer rated more than 500kVA. It is a gas-actuated relay mounted on the pipe connecting the main tank and conservator tank.
The function of the Buchholz relay is to protect the transformer from all internal faults
such as short circuit fault, inter-turn fault, etc.
[ ##eye## Surge impedance loading (SIL) of
Transmission line]
When short
circuit occurred in winding then it generates enough heat to decompose
transformer oil into gases ( hydrogen, carbon monoxide, methane, etc). These
gases move towards the conservator tank through a connecting pipe, then due to these gases, Buchholz relay gets activated. It sends signal to trip and alarm circuits and activate it. Then circuit breaker disconnects the transformer from the supply.
Oil conservator
The function of the oil conservator tank is to provide adequate space for expansion and contraction of transformer oil according to the variation in the ambient temperature of transformer oil inside the main tank.
It is a cylindrical drum-type structure installed on the top of the main tank of the transformer. It is
connected to the main tank through a pipe and a Buchholz relay mounted on the
pipe. A level indicator is also installed on the oil conservator to indicate the
quantity of oil inside the conservator tank. It is normally half-filled with
transformer oil.
Breather
Breather is a cylindrical container filled with silica gel and directly connected with the conservator tank of the transformer.
The main function of the breather is to supply moisture-free fresh air to the conservator tank during the expansion and contraction of transformer oil. This is because the transformer oil when reacting with moisture can affect the insulation and cause an internal fault in a transformer. That's why the air entering in conservator tank should be moisture free for better life of transformer oil.
In a breather, when air passes through
silica gel then moisture present in the air is absorbed by silica gel crystal and
hence a moisture-free dry air is supplied to the conservator tank. Thus we can also say that breather is acting as an air filter for the transformer.
Explosion vent
Explosion vent is a metallic pipe with a diaphragm at one end and installed on the main tank slightly above than conservator tank. It is available only in high rated power transformer.
The main function of the explosion vent is to protect power transformer against explosion during excessive pressure build up in the main tank due to severe internal faults. It acts as an emergency exit for oil and hot air gases inside the main tank of the transformer.
[ ##eye## What is Earth fault? - it's causes, effects and protection ]
The explosion vent works on the same principle as the safety valve works in the pressure cooker. Hence In other words we can also called the explosion vent as safety valve of the transformer.
Radiator and fans
Since
power losses in the transformer are dissipated in the form of heat. So a cooling
arrangement is required for the power transformer. Dry-type transformers are
generally natural air-cooled. But when we talk about oil-immersed transformers
then several cooling methods are used depending upon kVA rating, power losses,
and level of cooling required.
Hence to provide proper cooling, radiators and fans are installed on the main tank of the power transformer. Radiators are also called cooling tubes.
The main function of cooling tubes or radiators is to transfer heat generated by core and windings to the environment by circulating heated oil throughout the cooling tubes.
In a large power transformer, forced cooling is
achieved with the help of cooling fans fitted on the radiator.
Read more articles:
Very good article..
ReplyDeleteNicely explained
ReplyDeleteVery good article... Explained in simple and easy language to the point..
ReplyDeleteNicely explained
ReplyDeleteVery nice article. Simple understanding
ReplyDeleteVery good Article .
ReplyDeletePlease explain transformer in detail
ReplyDeletevery good explained
ReplyDeletenicely explained
ReplyDeleteI like this 👌😊
ReplyDelete