What is Transformer? transformer definition & working principle

The two transformer winding are on separate parts of the silicon steel core.

What is a Transformer?

The working principle of a transformer is as the transformers are static devices that transfer electrical energy from one circuit to another by the phenomenon of electromagnetic induction without any change in frequency. They can link circuits that have different voltages, which is one of the enabling factors for the universal use of the alternating current (AC) system for the transmission and distribution of electrical energy.

Working Principle of Transformer

The transformer is an electromagnetic conversion device in which the electrical energy received by its primary winding is first converted into magnetic energy, which is reconverted into electrical energy in other circuits is the working principle of a transformer (secondary winding, tertiary winding, etc.). Thus, the primary and secondary windings are not connected electrically but coupled magnetically. A transformer is tunned either a step-up transformer or a step-down transformer depending upon whether the secondary voltage is higher or lower than the primary voltage. Transformers can be used to either step-up voltage or step-down voltage depending upon the need and application. Hence, their windings are referred to as high voltage now-voltage or high-tension/low-tension windings instead of primary/secondary windings.

Transformer Theory

A clear understanding of how transformers work is necessary in order to wire them properly in an electrical system. Understanding input and output current and grounding are particularly troublesome. A dual-voltage transformer can be ruined when power is applied if the connections are made improperly.

An important property of electricity is that a magnetic field is produced around a wire in which electrical current is flowing, Figure 1. The more current that flows, the stronger is the magnetic field. An even stronger magnetic field can be produced by winding the wire into a coil. Now the magnetic fields of adjacent wires add together to form one strong magnetic field.

when electrical current flows through a wire , a magnetic field built up around the wire.
fig 1 : when electrical current flows through a wire , a magnetic field built up around the wire.

The electrical current flowing in a transformer is an alternating current. The current flows first in one direction, stops, then reverses and flows in the other direction. The magnetic field around the winding is constantly in motion. Figure 2 shows the magnetic field during one cycle. Notice that the north and south poles of the magnetic field reverse when the flow of current reverses.

when alternating curret is flowing in the coil, the magnetic field is constantly moving(The arrow indicate electron flow.)
fig 2- when alternating current is flowing in the coil, the magnetic field is constantly moving(The arrow indicate electron flow.)

Another property of electricity is important to the operation of a transformer. When a magnetic field moves across a wire, a voltage is induced into the wire, figure 3. If the wire forms a complete circuit, the current will flow in the wire. If the second coil of wire is placed in a moving magnetic field, then a voltage will be induced in this second coil, Figure 4. This phenomenon is called mutual induction. An alternating current in one winding produces a moving magnetic field that induces a voltage in a second winding. Electrical energy is converted into a magnetic field and then converted back into electrical energy in a second winding. The trick is to do this with little or no loss of energy.

fig 3 – When the magnetic field moves across this wire, an electrical current flows in the wire
Fig 4 – The two transformer winding are on separate parts of the silicon-steel core.

The magnetic field loses strength quickly in the air therefore, a special steel core is used. The core is composed of thin sheets of a silicon-steel alloy. The magnetic field is concentrated in the core, and energy losses are reduced to a minimum. Figure 4 shows the two windings separated. Most transformers have one winding placed directly over the other to further reduce the loss of energy, as shown in figure 5.

Fig 5 – In most transformers, the two windings are placed one over the other to reduce energy losses.

Transformer Parts And Construction

There are three main parts of a electrical transformer:

  1. Primary Winding of Transformer
  2. Magnetic Core of Transformer
  3. Secondary Winding of Transformer

Primary Winding of Transformer

The primary winding of a transformer is connected to the input voltage supply and converts or transforms the electrical power into a magnetic field. While the job of the secondary winding is to convert this alternating magnetic field into electrical power producing the required output voltage.

Magnetic Core of Transformer

The magnetic core of an electrical power transformer comprises primary, secondary and tertiary windings. With primary windings on one side and secondary windings on the opposite, magnetic flux in between is what connects them on the core, allowing current to flow.

Secondary Winding of Transformer

secondary winding is the winding of a transformer that receives its energy by electromagnetic induction from the primary winding. The secondary winding is facilitated with larger-gauge wire because of the increase in current, whereas the primary winding is made up of smaller-gauge wire due to less current conduction.

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