Working principle of travel transformer

At the beginning of the new year, it has given us new opportunities and possibilities. Many people choose to travel together in this hopeful season, to meet new friends and see different scenery. When traveling, most people choose to buy a travel transformer to solve the problem of inconsistent voltage in other countries. So, what is the working principle of a travel transformer?

definition

Power Electronic Transformer (PET), also known as Electronic Power Transformer (EPT), is an advanced equipment that uses power electronics technology to achieve energy transfer and power conversion. This device includes solid-state transformers (SST) and flexible transformers (FT), which combine power electronic conversion technology and high-frequency energy conversion technology based on electromagnetic induction principles to transform the energy of one power characteristic into the energy of another power characteristic. These features mainly include the amplitude, frequency, phase, number of phases, phase sequence, and waveform of voltage (or current).

characteristic

As a new type of power conversion equipment, power electronic transformers not only have the basic functions of traditional power transformers, such as voltage conversion, electrical isolation, and energy transfer, but also can achieve additional functions such as power quality regulation, system flow control, and reactive power compensation. This is due to the introduction of power electronic conversion technology and control technology, which enables it to flexibly handle and control the amplitude and phase of voltage or current on both sides of the transformer, as well as control the system flow according to actual needs. Therefore, power electronic transformers can achieve more stable and flexible transmission, solve various problems in the power system, and show broad application prospects.

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

1. Small size and light weight;

2. Adopting air cooling, without the need for insulation oil isolation, reducing pollution, convenient maintenance, and high safety;

3. Can make the secondary side of the transformer output a constant amplitude voltage;

4. Can improve power quality, achieve sinusoidal input current and output voltage, and achieve unit power factor; The voltage and current on both sides of the transformer are controllable, and the power factor can be adjusted arbitrarily;

5. Equipped with circuit breaker function, high-power power electronic devices can instantly turn off high fault currents, eliminating the need for relay protection devices.

In addition, power electronic transformers also have some special applications, such as connecting batteries to improve power supply reliability, achieving special transformation functions from three-phase to two-phase or three-phase to four equal, and outputting AC and DC electricity at the same time. In the literature, through simulation comparison and analysis of conventional power transformers and self balancing power electronic transformers, the results show that PET has better input-output characteristics under different working conditions, and shows superior performance compared to traditional power transformers.

Development Overview
The concept of power electronic transformers can be traced back to the early 1970s, when W McMurray first proposed a power electronic topology circuit that includes a high-frequency transformer. Subsequently, the development of power electronic transformers accelerated in the late 1990s, especially with the proposal and experimental verification of research schemes in industrial distribution systems. Some new power electronic transformer structures are gradually emerging, including structures based on direct AC/AC conversion and three-level structures composed of input stage, isolation stage, and output stage.

In 1996, Koosuke Harada from Japan proposed the concept of intelligent transformers, which improve the utilization of transformer core materials through high-frequency technology, and achieve functions such as power factor correction, constant voltage, and constant current. Although these functions were achieved on a 200V/3kVA experimental setup, the efficiency is still slightly low, around 80% to 90%.

Overall, power electronic transformers have made significant progress in the continuous technological evolution, providing more possibilities for the stable and reliable operation of the power system.

A simple transformer consists of a closed magnetic conductor and two windings. One winding is connected to the AC power supply and is called the primary winding Np, while the other winding can be connected to the load and is called the secondary winding Ns. In the no-load state, when the primary winding is connected to the AC voltage Ui, an alternating current Io is generated in the transformer, which is called the no-load current. This current establishes an alternating magnetic flux that closes along the magnetic circuit of the magnetic core, passing through both the primary and secondary windings, generating self induced electromotive force E1 in the primary winding and mutual inductance electromotive force E2 in the secondary winding, satisfying the relationship of E1: E2=Np: Ns, where Np is the number of turns in the primary winding and Ns is the number of turns in the secondary winding.

In electronic circuits, transformers play important roles such as boosting, reducing voltage, isolating, rectifying, variable frequency, inverting, impedance matching, inverting, energy storage, filtering, etc.
The commonly seen travel transformer on the market now is DOACE112P, and this is his manual

About this item
●【Newest Upgraded Converter for 110V/ 120V Devices】2-prong AC converter socket can step down foreign voltage from 220-240V to 110V/120V, designed for US standard devices when Americans travel to 220-240V countries, such as Conair/ Babylisspro/ Revlon hair styling tools (hair straightener, flat iron, curling iron) and hair dryers (except Dyson), steam irons, electric kettle etc.
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●【Silent Working & Safety Assurance】Instead of noise fans, we adopt new cooling technique, it is more quieter and stable. Built in auto shut-off protection in case of over voltage / over current / short circuit / over temperature / over load and Surge Protection. Patent Reserved. Products passed and implemented ROHS, FCC, CE, ETL certification.
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Reference article: Science Popularization China - Science Encyclopedia - Electronic Transformers