Principles of Electronic Transformers

Principles of Electronic Transformers - Introduction

Electronic transformers, also known as switch regulated power supplies, are devices that use the principle of electromagnetic induction to transmit electrical energy or signals. They play a role in boosting, reducing voltage, isolating, rectifying, converting, inverting, impedance matching, inverting, energy storage, filtering, and other functions in electronic circuits.

Electronic transformers have the advantages of small size, lightweight, and low price, and are widely used in various electrical appliances.

The basic form of an electronic transformer is that two sets of coils with wires are inductively connected. When an AC (with a certain known frequency) flows to one of the coils, an AC voltage with the same frequency is induced in the other group of coils, and the magnitude of the induced voltage depends on the degree of coupling and magnetic flux linkage between the two coils.

Principles of Electronic Transformers - Structure

The basic structural components of an electronic transformer are the iron core and winding, which make up the transformer body. To improve the heat dissipation conditions, the bodies of large and medium capacity transformers are immersed in a closed oil tank filled with transformer oil, and the connections between each winding and the external circuit are led out through insulation sleeves. To ensure the safe operation of the transformer, there are also accessories such as an oil storage tank, gas relay, and air duct. In summary, the electronic transformer core, winding, oil tank, accessories, etc. are composed of:

1) The iron core is the magnetic circuit part of a transformer, consisting of an iron core column (with a winding set on the column) and an iron yoke (connecting the iron core to form a closed magnetic circuit). To reduce eddy current and hysteresis losses and improve the magnetic conductivity of the magnetic circuit, the iron core is made of 0.35mm-0.5mm thick silicon steel sheets coated with insulation paint and staggered. The function of an iron core is to strengthen the magnetic coupling between two coils. The cross-section of the iron core of small transformers is rectangular or square, while the cross-section of the iron core of large transformers is stepped, to fully utilize space.

2) The winding is the circuit part of a transformer, which is wound with copper or aluminum wire. The primary and secondary windings are concentric sheathed on the iron core column. For the convenience of insulation, usually the low-voltage winding is inside and the high-voltage winding is outside. However, for large-capacity low-voltage and high-current transformers, considering the difficulty of the outgoing line process, the low-voltage winding is often sleeved outside the high-voltage winding.

3) The oil tank is equipped with the body and transformer oil. To facilitate heat dissipation, some tank walls are welded with heat dissipation pipes. The function of transformer oil is insulation and cooling.

4) The attachment contains many components, but due to space limitations, we will not introduce them one by one, as shown in the following figure.

Principles of Electronic Transformers - Operating Principles

Although electronic transformers vary in size and use, their basic structure and working principle are the same. It is made using the principle of electromagnetic induction, and its main function is to transmit electrical energy or signals from one circuit to another. It is an important component for electrical energy transmission or signal transmission. The schematic diagram of the electronic transformer is shown in the following figure:

The main components of an electronic transformer are an iron core and two windings sheathed on the iron core. Two windings only have magnetic coupling but no electrical connection.

When an alternating voltage is applied to the primary winding of a transformer, alternating magnetic flux is generated in the iron core, and electromotive forces e1 and e2 are induced in the two windings, respectively.