The transformer is a static device that changes electrical energy from one circuit to another circuit with the help of mutual induction (without any connection) between two windings namely primary winding and secondary winding. It changes power from one circuit to another circuit without altering its frequency, but may be on changing voltage level. This is the simple definition of transformer. This article discusses what is transformer, basic theory and why this only works with AC.
What is a Transformer?
The transformer is a static device, that contains of one or more windings that are coupled magnetically and separated electrically with a magnetic core. It transmits the electrical energy from one circuit to the other by the principle of electromagnetic induction. The primary winding is defined as, the winding connected to the main supply, whereas, the secondary winding is the winding is connected to the load. The two windings with appropriate insulation are wound on a coated core which provides a magnetic pathway between windings.
When the main winding is supported by changing voltage source, an alternating magnetic flux will be created in the transformer core. This magnetic flux amplitude depends on the and the number of turns on the primary side, the frequency of the supply, applied voltage magnitude.
This flux flows through the core and later links with the minor winding. Based on the electromagnetic induction principle, this magnetic connecting induces a voltage in the minor winding. This is named as mutual induction between two circuits. The secondary voltage in the transformer depends on the number of turns on the secondary as well as frequency and magnetic flux.
Transformers are widely used in electrical power systems to generate the variable values of current and voltage at the same frequency. Thus, by a suitable primary and secondary turns proportion preferred voltage ratio is gained by the transformer.
Construction of Transformer
The essential parts of a transformer mainly include the primary winding, secondary winding and magnetic core
Primary Winding of Transformer: This type of transformer produces magnetic flux when it is associated with the electrical source.
Magnetic Core of Transformer: In this type of transformer, the magnetic flux produced by the main winding, that will permit through this low reluctance track connected with secondary winding and make a closed magnetic circuit.
Secondary Winding of Transformer: In this type of transformer, the flux produced by the primary winding that passes through the core and that will connect with the secondary winding. This winding also wounds on the similar core and gives the preferred o/p of the transformer.
Working Principle of Transformer
The working principle of transformer is very simple. It depends upon Faraday’s law of electromagnetic induction. Actually, mutual induction between two or more winding is responsible for transformation action in an electrical transformer.
Faraday’s Laws of Electromagnetic Induction
According to these Faraday’s laws, “Rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil”
Basic Theory of Transformer
Say you have a single winding which is supplied by an alternating electrical source. The alternating current (AC) through the single winding generates a frequently changing flux that surrounds the winding. If some other winding is carried nearer to the previous one, apparently some portion of the flux will tie with the second. As this flux is frequently changing in its amplitude and direction, there must be a modification in flux connection in the second winding or coil.
According to “Faraday’s law of electromagnetic induction”, there must be an EMF made in the second. If the circuit of the second winding is closed, there must be a flow of current through it.
This is the simplest procedure of electrical power transformer and this is the most basic working principle of transformer. For well understanding, we are trying to recurrence the above description in a briefer way here.
When we apply AC (alternating current) to an electric coil, there will be an irregular flux nearby that coil. Now if we take another coil near the first one, there will be an alternating flux connection with that second coil. As the flux is alternating, there will be clearly a rate of change in flux linkage with respect to time in another coil. Obviously e.m.f will be induced according to the Faraday’s law of electromagnetic induction. This is the most simple concept of the theory of transformer.
- The relation between the voltages in the coils is similar as the ratio of the No.of turns in the coils.
- Primary voltage or secondary voltage = turns on primary / turns on the secondary. This can also be written as
Vp/Vs = Np/Ns
- Step up transformers have additional turns of the minor coil than they do on the main coil.
- Step-down transformers have less turns on the minor coil than they do on the main coil.
Why Transformers Only Works With Alternating Current
A transformer requires an AC that will form a changing magnetic field. This also includes a varying voltage in a coil. This is the basic function of how a transformer works
- The main coil is linked to an AC supply.
- AN AC flows through a main coil wrapped around a soft iron core
- The altering current generates a changing magnetic field.
- This makes an alternating voltage in the minor coil.
- This makes an AC in the circuit associated to the secondary coil.
It’s significant to know that
- There is no electrical connection between the two coils.
- These only work if alternating current is supplied to the main coil. If DC was supplied, there would be no flow of current in the minor coil.
- As the current in the main coil growths steadily or falls steadily, there is a constant voltage induced in the minor coil.
- As the voltage in the first coil reaches extreme strength the voltage made in the minor coil is at its zero voltage.
Thus, this is all about why transformers only work with alternating current. We hope that you have got a better understanding of this concept.Furthermore, any doubts regarding this concept or to implement any electrical projects, please give your valuable suggestions by commenting in the comment section below. Here is a question for you, what is the function of a transformer?