Electronic transformer

The electronic transformer has an electronic device that converts the alternating voltage of the commercial power into a direct current and then forms a high-frequency alternating current voltage output through the semiconductor switching device and the electronic component and the high-frequency transformer winding, and is also described in the electronic theory. A crossover inverter circuit. Simply put, it is mainly composed of a high-frequency transformer core (core) and two or more coils, which do not change position from each other, from one or two electrical circuits, through AC power Magnetic induction, converted into AC voltage and current. At the output of the high-frequency transformer, one or more power circuits are supplied with high-frequency alternating current or direct current of different voltage levels.

Overview

A simple transformer consists of a closed magnetizer and two windings. One of the windings is connected to an AC power source, called the primary winding Np, and the other winding can be connected to the load, called the secondary winding Ns.

If the primary winding is connected to the power supply of the AC voltage Ui, the transformer is unloaded, and an alternating power supply Io is generated in the primary winding, Io is called no-load current. This current establishes an alternating magnetic flux that is closed along the magnetic circuit of the magnetic core. The magnetic flux passes through both the primary winding and the secondary winding, producing a self-induced electromotive force E1 in the primary winding, and a secondary electromotive force E2 in the secondary pole, then E1:E2 =Np:Ns. Np is the primary winding turns and Ns is the secondary winding turns.

The transformer plays the role of boosting, stepping down, isolation, rectification, frequency conversion, phase inversion, impedance matching, inverter, energy storage and filtering in the electronic circuit.

classification

Electronic transformers, together with semiconductor switching devices, semiconductor rectifying devices, and capacitors, are called the four main components in power supply devices. According to the role in the power supply unit, the electronic transformer can be divided into:

1) Power transformers, power transformers, rectifier transformers, inverter transformers, switching transformers, pulse power transformers that function as voltage and power converters;

2) Broadband transformers, audio transformers, and mid-cycle transformers that transmit broadband, audio, mid-cycle power and signals;

3) A pulse transformer that transmits pulses, drives and trigger signals, drives the transformer, and triggers the transformer;

4) an isolating transformer that acts as an isolation barrier between the primary and secondary sides, and a shielded transformer that acts as a shield;

5) A phase-change transformer that functions as a single-phase-changing three-phase or three-phase to single-phase, and a phase-shifting transformer (phase shifter) that changes the phase of the output;

6) A frequency multiplying or frequency dividing transformer that changes the output frequency;

7) a matching transformer that changes the output impedance to match the load impedance;

8) A voltage regulator transformer (including a constant voltage transformer) or a steady current transformer that functions as a stable output voltage or current, and a voltage regulating transformer that regulates the output voltage;

9) a filter inductor that functions as an alternating current and a direct current filter;

10) an electromagnetic interference filter inductor that suppresses electromagnetic interference, and a noise filter inductor that suppresses noise;

11) a absorbing inductor that absorbs a surge current and acts as a snubber inductor that slows the rate of change of current;

12) an energy storage inductor functioning as a reversing inductor for assisting the commutation of the semiconductor switch;

13) a magnetic switch inductor and a transformer functioning as a switch;

14) a controllable inductor and a saturating inductor that regulate the inductance;

15) Voltage transformer, current transformer, pulse transformer, DC transformer, zero flux transformer, weak current transformer, zero sequence current transformer, Hall current voltage detector for transforming voltage, current or pulse detection signals .

As can be seen from the above list, whether it is DC power, AC power, or special power supply, it is inseparable from the electronic transformer. Some people define the power supply as a DC power source and an AC power source that are converted by high frequency switching. When introducing the role of soft magnetic electromagnetic components in power supply technology, various electromagnetic components in high frequency switching power supplies are often exemplified. At the same time, among the soft magnetic electromagnetic components used in electronic power sources, various transformers occupy a dominant position, and therefore transformers are used as representatives of soft magnetic components in electronic power sources, and they are called "electronic transformers".

Characteristics

Electronic transformer, the input is AC220V, the output is AC12V, and the power can reach 50W-300W. It is mainly a transformer circuit developed on the basis of high-frequency electronic ballast circuit. Its performance is stable, small in size and large in power, thus overcoming the shortcomings of traditional silicon steel sheet transformers, such as large size, heavy weight and high price.

An electronic transformer is an unregulated switching power supply, which is actually an inverter. First, the alternating current is rectified into direct current. Then, a high-frequency oscillator is formed by electronic components to convert the direct current into a high-frequency alternating current, and the required voltage is output through the switching transformer and then rectified for use by the electric appliance. Switching power supplies have the advantages of small size, light weight and low price, so they are widely used in various electrical appliances.

According to the driving method of the high-frequency switch tube, it can be divided into a self-excited oscillation type and a other excitation type.

Acceptance test

(1) measuring the DC resistance value of the winding at each tap position;

(2) Detecting whether the voltage ratio of each tap position matches the nameplate;

(3) determining the polarity of the winding and the label of the joint group;

(4) Remove the iron core grounding piece, use 2500V megger to check the insulation condition of the iron core, and install the grounding piece after the requirements, and check whether the iron core is grounded well (the iron core can only be grounded a little);

(5) Power frequency withstand voltage test, the capacity of 800KVA or less can pass the power frequency withstand voltage test, the capacity is 800KVA and above, and the power frequency voltage is applied when there are conditions, according to the requirements of GB50150-90 standard.

(6) Use 2500V megohmmeter to check the insulation condition of transformer high voltage to ground, low voltage to ground and high voltage to ground pressure.