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The composition and application of AC Automatic Voltage Regulator (AVR)

2020-07-14

The composition of AC Automatic Voltage Regulator (AVR)


AC automatic voltage regulator (AVR) is mainly composed of four parts: power transformer, rectifier circuit, filter circuit and voltage regulator circuit.


1. Power Transformer

The power transformer is a soft magnetic electromagnetic component. Its functions are power transmission, voltage conversion and insulation isolation, and it is widely used in power supply technology and power electronics technology.


2. Rectifier circuit

A "rectifier circuit" (recTIfying circuit) is a circuit that converts AC power into AC power. Most rectifier circuits consist of transformers, rectifier main circuits and filters. It is widely used in the fields of AC motor speed regulation, generator excitation adjustment, electrolysis, electroplating and other fields. Rectifier circuit is usually composed of main circuit, filter and transformer. After the 1970s, the main circuit was mostly composed of silicon rectifier diodes and thyristors. The filter is connected between the main circuit and the load, and is used to filter out the AC component in the pulsating AC voltage. The setting of the transformer depends on the specific situation. The role of the transformer is to achieve the matching between the AC input voltage and the AC output voltage and the electrical isolation between the AC power grid and the rectifier circuit.


The function of the rectifier circuit is to convert the low-voltage alternating current output by the alternating current step-down circuit into a unidirectional pulsating alternating current. This is the rectification process of the alternating current. The rectifying circuit is mainly composed of rectifying diodes. The voltage after passing through the rectifier circuit is no longer AC voltage, but a mixed voltage containing AC voltage and AC voltage. It is customarily called unidirectional pulsating AC voltage.


3. Filter circuit

The filter circuit is often used to filter the ripple in the rectified output voltage. It is generally composed of reactive components, such as a capacitor C in parallel across the load resistance, or an inductor L in series with the load, and various complex types composed of capacitors and inductors. Filter circuit.


4. Voltage regulator circuit

Voltage regulator circuit refers to a circuit that can keep the output voltage constant when the input voltage, load, ambient temperature, circuit parameters, etc. change. This circuit can provide stable AC power and is widely used in various electronic devices.


Main technical indicators of AC Automatic Voltage Regulator (AVR)


The technical indicators of AC automatic voltage regulator (AVR) can be divided into two categories: one is the characteristic index, which reflects the inherent characteristics of the AC stabilized power supply, such as input voltage, output voltage, output current, and output voltage adjustment range; the other is the quality index , Reflecting the advantages and disadvantages of AC regulated power supply, including stability, equivalent internal resistance (output resistance), ripple voltage and temperature coefficient.


1. Characteristics

(1) Output voltage range

The output voltage range that can work normally under the conditions of AC regulated power supply. The upper limit of this index is defined by the maximum input voltage and the minimum input-output voltage difference, while the lower limit is determined by the reference voltage value inside the AC automatic voltage regulator .


(2) Maximum input-output voltage difference

This index characterizes the maximum allowable voltage difference between the input and output under the normal operating conditions of the AC automatic voltage regulator , and its value mainly depends on the withstand voltage index of the internal adjustment transistor of the AC automatic voltage regulator .


(3) Minimum input-output voltage difference

This index characterizes the minimum voltage difference between input and output required to ensure the normal operating conditions of an AC automatic voltage regulator.


(4) Output load current range

The output load current range is also called the output current range. Within this current range, the AC automatic voltage regulator should be able to ensure compliance with the specifications given in the specifications.


2. Quality index

(1) Voltage adjustment rate SV

The voltage regulation rate is an important index that characterizes the stability of the AC automatic voltage regulator. It is also called the stability factor or stability factor. It represents the degree of stability of the output voltage VO of the AC stabilized power supply when the input voltage VI changes. The percentage of the relative change of input and output voltage at unit output voltage.


(2) Current adjustment rate SI

The current regulation rate is a main self-index reflecting the load capacity of the AC automatic voltage regulator, and is also called the current stability factor. It characterizes the ability of the AC regulated power supply to suppress the fluctuation of the output voltage due to the change of the load current (output current) when the input voltage is unchanged. Under the conditions of the specified load current change, the output voltage is usually The percentage of the output voltage change represents the current regulation rate of the AC regulated power supply.


(3) Ripple suppression ratio SR

The ripple rejection ratio reflects the ability of the AC stabilized power supply to suppress the mains voltage introduced by the input terminal. When the input and output conditions of the AC stabilized power supply remain unchanged, the ripple rejection ratio often uses the input ripple voltage peak-peak and The output ripple voltage peak-to-peak ratio is generally expressed in decibels, but sometimes it can also be expressed as a percentage, or directly expressed as a ratio of the two.


(4) Temperature stability K

The temperature stability of the integrated AC stabilized power supply is a percentage value of the relative change in the output voltage of the AC stabilized power supply within the maximum change range of the specified operating temperature TI of the AC stabilized power supply (Tmin≤TI≤Tmax).


Use of AC Automatic Voltage Regulator (AVR)


AC regulated power supply is used for AC power supply of medical electronic instruments, communication and broadcasting equipment, industrial electronic equipment, scientific research, universities, laboratories, industrial and mining enterprises, electrolysis, electroplating, charging equipment, etc.


such as:

1. Test and aging of LED, energy-saving lamps and other lamps;

2. Sophisticated testing of resistors, relays, motors, etc.;

3. Switching power supply, power adapter;

4. Sophisticated machine; electronic component performance test, routine test;

5. Testing and aging of electric vehicle motors, controllers, AC motors;

6. Electrolysis, electroplating, corrosion aluminum foil processing, etc. LCD screen, touch screen and other displays;

7. Auto electronics, AC motors, motor controllers, cigarette lighters, audio and video testing aging, etc.;

8. Photovoltaic and inverter test aging;

9. Capacitors, resistors, relays, transistors, sensors and other electronic devices;

10. Aerospace, defense and military industry;


Matters needing attention when choosing AC regulated power supply:

1. When selecting AC regulated power supply, need to understand the input and input requirements of the instrument to be loaded? Need to know whether the input to be loaded is single-phase or three-phase?

2. Which functions are specifically satisfied? Such as power supply ripple, whether it has a communication interface or analog control, output accuracy requirements, programming functions, etc.

3. The power of the AC stabilized power supply is calculated for the maximum total power of the device. When the AC stabilized power supply is selected, the output power of the AC stabilized power supply cannot be lower than the total power of the device.

4. What is the input voltage and current of the AC stabilized power supply? When we choose the AC stabilized power supply, in addition to the need to understand the environmental mains voltage, we also need to understand the input voltage and current of the loaded equipment. When choosing the Han-Heng stabilized power supply, it is necessary to match the input voltage and current of the device.


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