Transformers

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Transformer structure and operation

Devices that convert voltage from one value to another without changing the frequency of alternating current are called transformers.

In transformers, two coils are mounted on a common core (Fig. 199). In this case, the windings on the first reel are called primary windings, and the windings on the second reel are called secondary windings.

The primary veil is U₁ let us connect to a voltage alternating current. The alternating current creates an alternating magnetic field in the coils. The magnetic field lines of this coil pass through the core to the secondary coil.
As a result, U in the secondary loop₂ voltage alternating induction current is generated. The frequency of this current is the same as the frequency of the current in the primary winding.
U in the secondary veil₂ the amount of voltage depends on the number of turns of wires in the primary and secondary windings. Experiments show that the number of windings in the secondary winding is many times less than the number of windings in the primary winding, and the voltage of the current generated in the second winding is many times less. Conversely, the greater the number of windings in the secondary winding, the greater the voltage in the secondary winding.
The number of packages in the primary wrap n₁, the voltage applied to it U₁, the number of packages in the second wrap n₂, the voltage generated in it is U₂ get In this case, the following expression is appropriate:

Hence, it is possible to change the voltage of the alternating current. This is an important feature of alternating current.

Changing the voltage in an alternating current conductor is called alternating current transformation.
A transformer is a device that transforms the voltage across an alternating current conductor.
The words ‘transform’ and ‘transformer’ are derived from the Latin word ‘transformo’, which means ‘I transform’.

Figure 200 shows the transformer and its designation in the circuit diagram.

Transformers are of two types.
If the voltage in the secondary winding of the transformer is greater than the voltage in the primary winding, such a transformer is called a step-up transformer.
In the step-up transformer n₂ > n₁ and U₂ > U₁ will be.
If the voltage at the secondary winding of the transformer is less than the voltage at the primary winding, such a transformer is called a step-down transformer.
In the step-down transformer n₂ <n₁ and U₂ <U₁ will be.

Energy cycle in a transformer
The transformer converts a certain voltage of electricity in the primary winding into electricity of another voltage in the secondary winding.
The current in the primary and secondary windings of the transformer is as follows:
P₁=I₁U₁ and P₂=I₂U₂.
The efficiency of advanced transformers is very high, 99-99,5%. In such transformers, the loss of electrical energy during transformation cannot be taken into account, i.e. P₁ = P₂ can be obtained. In that case:

In a transformer, the more the voltage in the secondary winding increases, the more the current decreases.

For example, the transformer primary winding U₁ Suppose = 220 V is connected to the mains. The voltage across the secondary winding is U₂ Let = 500 V. If the secondary circuit is connected to the consumer, the I in it₂ current in the first winding I₁ is 2,4 times less than the current.

To describe such a relationship, a quantity called the transformation coefficient (k) is introduced:

When k> 1, the transformer is called step-down, and when k <1, it is called step-up transformer.

Source: Physics textbook
National Encyclopedia of Uzbekistan
State Scientific Publishing House. T. 2010