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A stationary electromagnetic device that transforms electrical energy and transfers it from one circuit to another is called a transformer. In an AC circuit, the AC power supply, current and waveform can be changed with the help of a transformer. Each conversion is usually an electromagnetic transfer of energy to another circuit, and there is no direct connection with the circuit. However, it can also be transformed by electromagnetic and electrical means, and this transformer becomes an autotransformer.

It should be noted that the transformer transforms not one but several electrical parameters at the same time. For example, when the voltage is changed, the current also changes. Transformers occupy a very important position in electronic equipment, AC voltage and DC voltage in power equipment are almost obtained by transformers through conversion and rectification. In terms of circuit isolation matching and impedance conversion, most of them are realized by transformers.

A simple transformer consists of a closed magnetic conductor (iron core) and two windings. One of the winding is connected to the AC power supply, we call it the primary winding; The other winding is connected to the load and is called the secondary winding.

Electronic transformer classification

1. Classification by operating frequency

The working frequency of power transformer is 50HZ or 60HZ;

Medium frequency power transformer its operating frequency is 400 ~ 1000Hz;

The working frequency of the audio transformer is 20Hz-20kHz;

The working frequency of the super-audio transformer is more than 20KHz, generally not more than 100KHz;

High frequency transformer A transformer whose operating frequency is above 20Hz~100kHz.

2. Categorize by use

Power transformers are used to provide transformers required by electronic equipment, such as filament transformers, anode transformers, rectifier transformers, isolation transformers, etc.

Audio transformers are used in audio amplifying circuits and audio equipment transformers, such as microphone transformers, input transformers, interstage or interline transformers, output transformers, matching transformers, etc.

A transformer that works in a pulse circuit, such as a trigger transformer, intermittent oscillation transformer, regression transformer, inverting transformer, pulse output transformer, etc.

Switching power transformer used in switching power supply circuit transformers, such as single-end excitation transformer, single-end flyback transformer, half-bridge transformer, full-bridge transformer, etc.

High frequency transformer works in high frequency amplifier circuit and transmission circuit transformer, such as impedance matching transformer, input transformer, output transformer, transmission line transformer, etc.

Special transformer A transformer with a special function, such as parametric transformer, voltage regulator transformer, super isolation transformer, lighting transformer, magnetic leakage transformer, etc.

3 Classification by core structure

Shell type core transformer such as E1 type insert core transformer, XED type, ED type core transformer, the coil is surrounded by the core magnetic circuit, core type transformer such as port type insert core transformer, XCD type, CD type, R type core transformer, the core column is surrounded by the coil. Annular transformer This type of transformer has a circular core and its coils surround the core.

4. Sort by number of phases

Single-phase transformer works in single-phase circuit;

Three-phase transformer works in three-phase circuit;

Polyphase transformers work in circuits with more than three phases.

5 Type by moisture proof

This kind of transformer does not use special moisture-proof measures, generally used for impregnation of insulating paint, its moisture-proof performance is general, suitable for indoor better environmental conditions. Because of its simple process and low manufacturing cost, it is widely used in civil and household appliances.

Sealed transformer This type of transformer is best protected against moisture when it is sealed in a metal box. However, due to the high cost and large volume, most of them are used for military equipment or special requirements. Resin-encased transformer This kind of transformer after resin encapsulation, in a humid environment greatly delay the number of moisture into, reduce the amount of moisture into, moisture effect is good. Another advantage of resin encapsulation is to improve the insulation performance of the transformer and increase the heat dissipation capacity of the transformer. Commonly used resin encapsulation forms are: coil encapsulation, transformer encapsulation, coil encapsulation, transformer encapsulation and so on four kinds, its moisture-proof effect to the best encapsulation.