المحولات - اهمية المغنطيسية .. الإلكترونيات

Transformers - The importance of magnetism .. Electronics

Transformers

Transformers are considered one of the devices whose work depends on the electromagnetic effects of alternating current.

The transformer consists of two coils (68), one of which is called the primary N1, which is the coil that is connected to a specific source, such as an antenna amplifier or a source of alternating current, while the other coil is called the secondary N? It is the one that supplies the subsequent devices or circuits such as transistors, valves, microphones, motors and lamps with all the power they need.

The transformer may be without an iron core, and is called an antenna transformer, as in the case of transformers used in high-frequency circuits (69). When an alternating current passes through the primary coils, changing electromagnetic fields are created within them, the value of which increases and decreases according to the increase and decrease of the alternating currents induced in them. When these fields cut the secondary coils of the transformer, an electromotive force is generated in them by induction, which is used to supply devices and equipment.

69 - Air core transformer
70 - Iron core transformer

Iron core transformers are used in low frequency audio circuits. The iron cores around which the coils are wound help to concentrate the magnetic lines of force, and are generally made of metal foil (see p. 27).

It is possible to place the primary coils on one leg of the core and the secondary coils on the other leg (70). It is also possible to place the primary and secondary coils together on the middle leg of the core. The transformer is used to change or convert the voltage value according to the ratio of the number of turns in it or according to a specific relationship between the number of primary coils and the number of secondary coils (71).

71 - Transformer turn ratio.
72 - Typical power transformer.

In other words, if the number of turns in the primary is equal to the number of turns in the secondary, the voltage value that appears across the secondary terminals is exactly equal to the voltage value connected across the primary terminals, and the ratio of the number of turns is 1:01. However, if the number of turns in the secondary is one third of the number of turns in the primary, the ratio of the number of turns is 1:3. If an alternating voltage of 240 volts is connected across the primary terminals, we get a voltage of 80 volts across the secondary coil terminals. However, if the number of turns in the secondary of the transformer is twice the number of turns in the primary, i.e. the ratio of the number of turns is 2:1, the voltage across the secondary coil terminals becomes 480 volts. Transformers are used to raise or lower the electromotive force, and they are also used in electronic circuits to connect them (pair them) with each other. A transformer may have more than one primary coil or more than one secondary coil (72). One or both coils may be provided with interconnection points that allow the transformer to be connected to voltages of different values, such as 250/230/210 volts. As for the interconnection points in the secondary coils, we obtain from them several voltages with different values ​​according to need, which here are equal to 5 volts and 6.3 volts, in addition to a voltage of 500 volts resulting from a secondary coil with a baleen connection point in the middle.