What is a Transformer? Beginner's Guide

What is a Transformer

Introduction:

Do you know how electricity comes to your home from the power station? and also how some electric gadgets operate in high voltage? So what is the component used for this work? Of course, the component is an electrical transformer.


So what it is and how it works. If this question is arises in your mind and you want to know about what is a transformer, then this article is for you. In this tutorial, I am going to unlock the details of transformers. Here you will learn -

1. What is the transformer?
2. Types of the transformer.
3. How does the transformer work?
4. Transformer formulas.
5. Transformer losses.
6. How to test a transformer using a multimeter.
7. Application of the transformer.

What is a Transformer?


A transformer is an electrical device that can increase and decrease the magnitude of the voltage. In the transformer, two or more copper windings are wound on a laminated core of metal of iron and steel. These windings are magnetically coupled but electrically separated with insulation.

What is a Transformer

The winding which is connected to the main power supply is called the primary winding and the winding which is connected to the load or appliance is called secondary winding. when a voltage source is connected to the primary winding then it will energize and produced a magnetic flux or field in the transformer core.

This magnetic field depends on the magnitude of the applied voltage, frequency and also the number of turns in the primary coil. this magnetic flux circulates through the transformer core and links with the secondary coil based on the principle of electromagnetic induction.


This induced magnetic flux produces a voltage in the secondary coil is known as mutual induction. The secondary voltage depends on the number of turns on the secondary coil and also the magnetic flux and frequency.

Types of Transformer


In the electricity different types of electric transformer are used for different purposes like power generation, distribution, transmission and utilization of electrical power.

Transformers are distinguished based on the voltage levels, core construction, winding arrangements, uses, and nature of supply, etc.

Here we discuss different types of transformers like step-up and step-down transformer, air transformer, 1-Phase, 3-Phase transformer, and Autotransformer, etc. These different types of transformer are arranged below

1. Transformers based on voltage levels.
 A. Step-up transformer.
 B. Step-down transformer.

2. Transformer based on core construction.
 A. Air core transformer.
 B. Iron core transformer.

3. Transformer based on winding arrangement.
 A. Autotransformer.

4. Transformers based on usage.
 A. Power transformer.
 B. Distribution transformer.

5. Transformers based on the nature of supply.
 A. Single-phase transformer.
 B. Three-phase transformer.

What is a Transformer

1. Transformer based on voltage levels

A. Step-up transformer :

In the step-up transformer, the amount of voltage in the output is more than the input voltage. This is due to the more number of turns in the secondary coil compare to the primary coil.

These type of transformer are used to raise the voltage to a higher level. These are used in the transmission system.

B. Step-down transformer :

In the step-down transformer, the amount of voltage in the output is less than the input voltage. This is due to the less number of turns in the secondary coil compare to the primary coil.


These type of transformer are used to reduce the voltage to a lower level. These are used in the distribution system and in electronic circuits.

2. Transformer based on core construction

A. Air core transformer :

In the air-core transformer, both the primary and secondary windings are wound on a non- magnetic strip where the induction happened between the primary and secondary winding through the air.

For the use of air, the hysteresis and eddy current losses are completely eliminated in this core type transformer.

B. Iron core transformer :

In the iron-core transformer, both the primary and secondary windings are wound on multiple iron plate bunch where the induction happened between the primary and secondary windings through the iron.

These are the broadly used transformer in which the efficiency is high compared to the air-core transformer.

3. Transformer based on the winding arrangement

A. Autotransformer :

In an autotransformer, the primary and secondary windings are connected to each other in series both physically and magnetically.

In this type of transformer, voltage is varied according to the position of secondary tapping on the body of the coil winding.

4. Transformer based on usage

A. Power transformer :

The power transformer is the larger transformer which is used for high voltage power transfer applications. In this transformer, the insulation is very high.

B. Distribution transformer :

For the industrial purpose, domestic purpose and for the remote areas the distribution transformer is used. It is used for the distribution of electrical energy at low voltage is less than 33kV in industrial purpose, 440V-220V for domestic purpose.

5. Transformer based on the nature of supply

A. Single-phase transformer :

In the single-phase transformer, two winding is used to transform the voltage. The power rating of the single-phase transformer is less than compared with the three-phase transformer.

Mostly core type construction is used for this type of transformer. This type of transformer is used in the remote ends of the power distribution system.

B. Three-phase transformer :

In the three-phase transformer, three windings are used to transform the voltage. In this type of transformer, the primary and secondary windings are connected in the form of star-delta or delta-star shape depending on the requirements of the load voltage.

Transformer working


The function of the transformer is based on the principle of mutual induction between two coils or windings. When a voltage source is connected to the primary coil then it will energize and produce a magnetic flux or field in the transformer core.


According to Faraday's law of electromagnetic induction, this flux linkage with both primary and secondary windings induces an emf in them. This induced emf is directly proportional to the number of turns in it. And it is given as



In terms of r.m.s values, the voltage transformation ratio for an ideal transformer becomes



Where Vp is primary voltage and Vs is the secondary voltage.

In terms of ampere-turns balance



From the above equation, we get



This shows that for an ideal transformer the output power is equal to the input power.

Transformer formulas

The basic equation for the ideal transformer is given as



Where

Vp = Primary voltage.
Vs = Secondary voltage.
Np = number of turns in the primary coil.
Ns = number of turns in the secondary coil.
Ip = Primary current
Is = Secondary current.

The equation for the input power is given by



The equation for the output power is given by



Where

𝜃p = the primary phase angle.
𝜃s = the secondary phase angle.

In the windings, the magnetic flux varies sinusoidally, Ⲫ = ⲪmaxSin𝜔t, then the basic relationship between induced emf (e) in a coil winding of N turns is given by




 (when cos𝜔t = 1)



Where

f = the flux frequency in Hertz = 𝜔/2𝜋
N = the number of turns in the coil windings.
Ⲫ = the amount of flux in webers.

Transformer efficiency

In the transformer because of various kind of losses in practical the output power of the transformer is smaller than the input power and the ratio of this output power to the input power is called efficiency and it is defined as


Transformer losses


Basically, the transformer is a static device so it has no mechanical losses like friction but it consists of electrical losses like core or iron losses and copper losses.


1. Core losses and iron losses

Depending upon the magnetic properties of the material used for the construction of the core some losses have happened like hysteresis loss and eddy current loss.

What is a Transformer

A. Hysteresis loss in a transformer :

When the alternating current reverses in each cycle, tiny "magnetic domain" within the core material is reversed. these are physical changes within the core material and take up some energy.

This used energy depends on the "reluctance" of the core material. It is largely overcome by using special low reluctance steel core material.

B. Eddy current loss in a transformer :

When the primary winding is energized then it produces magnetic flux or field in the transformer core this flux links with secondary windings induces an emf and produces the current. the value of current depends upon the amount of emf and the resistance of the system.


Since the core is made of conducting material, this emf circulates current through the body of the material. This circulating current is called eddy current.

These currents are not responsible for doing any useful work and it produces a loss. In the transformer, this loss is known as eddy current loss.

2. Copper loss

In the transformer, the primary and secondary windings are made by copper wire and it has an internal ohmic resistance. This resistance produced the copper loss.

The copper loss for the primary winding is


and the copper loss for the secondary winding is


Therefore, the total copper loss will be


Where Ip and Is are the primary and secondary current respectively, Rp and Rs are the resistance of the primary and secondary winding respectively.

Testing of a transformer using a multimeter

1. Continuity testing of a transformer

Set the multimeter at continuity mode and connect the two leads of the meter across the primary winding terminals and see if the buzzer of the multimeter is responding then the primary connection is good.

Similarly, test the secondary windings and see if the buzzer is running then overall the transformer is in good condition.

2. Identifying the primary and secondary winding of the transformer

A. For step-up transformer :

Set the transformer at the ohm range and connect the two leads of the meter at any winding. See the multimeter and note the reading. Again repeat the process for other winding.

See the multimeter and note the reading, if in the first case the value of the resistance is bigger than the second case then obviously the first winding is secondary and the other is primary.


This is why because the number of turns in the primary winding is much more than secondary so the resistance is high.

B. For step-down transformer :

Similarly set the transformer, and see if the first case the value of the resistance is bigger than the second case then obviously the first winding is primary and other is secondary.

This is why because the number of turns in the primary windings is lower than secondary so the resistance is low.

Application of the transformer


The main application of the transformer is to step up (Increase) and step down (Decrease) the level of the voltage. In other words, increase or decrease the level of current, while power must be the same.

According to the necessity, some kind of transformers are used like

Power transformer

These types of transformers are used for high voltage power transfer applications (more than 33kV).

Distribution transformer

these types of transformers are used to distribute the generated power to a distant location. It distributes low voltage that is less than 33kV in industry and 220V-440V for household porpuses.


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