What is A ​​​​​​​Electronic Transformer?

Electronic transformer is an electronic device that converts the alternating voltage of mains into direct current and then forms a high-frequency alternating voltage output through semiconductor switching devices, electronic components and high-frequency transformer windings. A kind of AC-DC-AC inverter circuit. In simple terms, it is mainly composed of a high-frequency transformer core (iron core) and two or more coils, which do not change their positions. The effect of magnetic induction is converted into alternating voltage and current. At the output end of the high-frequency transformer, high-frequency alternating current or direct current of different voltage levels is supplied to one or more than two power circuits.



Power Electronic Transformer (PET), also known as Electronic Power Transformer (EPT), Solid State Transformer (SST) and Flexible Transformer (FT), is an energy New transformers for transmission and power conversion. By analyzing and summarizing the existing topological structure of power electronic transformers, the following definitions can be made for power electronic transformers: The so-called power electronic transformer is a combination of power electronic conversion technology and high-frequency electric energy conversion technology based on the principle of electromagnetic induction. A static electrical device that implements the transformation of electrical energy of one electrical characteristic into electrical energy of another electrical characteristic. The power characteristics of electric energy mentioned here mainly refer to the amplitude, frequency, phase, number of phases, phase sequence and waveform of voltage (or current).

1. Features

Electronic transformer is a new type of power conversion equipment. It not only has the basic functions of voltage conversion, electrical isolation and energy transfer of traditional power transformers, but also can realize power quality adjustment, system power flow control and reactive power compensation. Other additional functions. The reason why the power electronic transformer can realize these additional functions is mainly because it can flexibly process and control the amplitude and phase of the voltage or current of the primary and secondary sides of the transformer after introducing power electronic conversion technology and control technology. , and the power flow of the system can be controlled according to actual needs. Therefore, the power electronic transformer can realize more stable and flexible power transmission, can solve many problems existing in today's power system, and its application prospect will be very broad.

Compared with traditional power transformers, PET has the following characteristics:

①Small size and light weight;

②It can be cooled by air, does not need insulating oil for isolation, reduces pollution, and is easy to maintain and safe;

③ It can make the secondary side of the transformer output a voltage of constant amplitude;

④ It can improve the power quality, can obtain the input current and output voltage of sinusoidal waveform and can achieve unity power factor, and the voltage and current on both sides of the transformer are controllable, so the power factor can be adjusted arbitrarily;

⑤ With the function of circuit breaker, high-power power electronic devices can instantaneously (within micro-level time) shut off large fault currents, eliminating the need for relay protection devices.

In addition, the power electronic transformer also has some special purposes, such as: after connecting with the battery, it can improve the reliability of the power supply; it can realize the special transformation function of three-phase to two-phase or three-phase to four-phase; it can output alternating current and direct current at the same time. In the literature, the author compares and analyzes conventional power transformers and self-balancing power electronic transformers by simulation. The literature mainly conducts simulation research on five working conditions. It has good input and output characteristics under the conditions of one-phase disconnection, three-phase short circuit, and three-phase unbalanced voltage on the high-voltage side and harmonic pollution, which can avoid the unbalance of one side of the system to the other side of the system. Therefore, it has better performance than conventional power transformers.

2. Classification

A. Classified by working frequency:

Power frequency transformer: working frequency is 50Hz or 60Hz

Intermediate frequency transformer: working frequency is 400Hz or 1KHz

Audio Transformer: Operating frequency is 20Hz or 20KHz

Super audio transformer: above 20KHz, not more than 100KHz

High-frequency transformer: The operating frequency is usually above KHz to hundreds of KHz.

B. Classified by use:

Power Transformer: Transformer used to provide power required by electronic equipment

Audio Transformers: Transformers for audio amplifier circuits and audio equipment

Pulse transformer: a transformer working in a pulse circuit, its waveform is generally a unipolar rectangular pulse wave

Special transformers: transformers with a special function, such as parametric transformers, voltage regulator transformers, ultra-isolation transformers, transmission line transformers, magnetic leakage transformers

Switching power supply transformers: transformers used in switching power supply circuits

Communication transformer: transformer used for DC isolation and filtering in communication network

3. Material

Electronic transformer materials mainly include

Skeleton (Bobbin, Base, Case)

Copper Wire

Ferrite Core, SI-Steel Lamination

Copper Foil

Insulation tape (Tape)

Safety tape, also known as Margin Tape

Tube

Chemical materials: Solder Bar, Varnish, Epoxy, Glue, Thinner, Scaling Powder, Ink

4. Process Flow

1) Preprocessing, such as copper foil, skeleton, etc.; (beforehand process)

2) winding; (winding coil)

3) Wire management (wiring) (termianl lead wire);

4) Solder 1; (dip solder 1)

5) Combined magnetic core, including dispensing and wrapping tape; (assembly)

6) Test one; (test 1)

7) Bake glue; (bake glue)

8) Immersion; (dip varnished or vacuumed varnish)

9) Bake varnish; (bake varnish)

10) Solder 2; (dip solder 2)

11) test two; (test 2)

12) Appearance inspection and cleaning; (inspection & cleaning)

13) Finished product packaging; (packing)