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AC voltage regulator



Basic principle

Although there are many types of AC voltage stabilizers, the working principles of the main circuit are different, but basically (except for AC parameter voltage stabilizers) are basically input switch sampling circuits. Control circuit, voltage

Regulating device, output protection device, driving device, display and its composition. The basic working principle block diagram is as follows:

1. Input switch: as the voltage regulator input Working switches generally use air-switch type small circuit breakers with limited current protection, which can protect the voltage stabilizer and electrical equipment.

2. Voltage regulator: It is a device that can regulate the output voltage. It can increase or decrease the output voltage and is the most important part of the voltage regulator.

3. Sampling circuit: It detects the output voltage and current of the regulator, and transmits the output voltage change to the control circuit.

4. Drive device: Since the control electrical signal of the control circuit is weak, a drive device is needed for power amplification and conversion.

5. Drive protection device: a device that connects and disconnects the output of the voltage stabilizer. Generally, relays, contactors, or fuse are commonly used.

6. Control circuit: It analyzes the sampled circuit detection model. When the output voltage is too high, it sends a control signal to the drive device to reduce the voltage, and the drive device will drive the voltage regulator to The output voltage is adjusted down. When the output voltage is low, a control signal to increase the voltage is sent to the driving device, and the driving device will drive the voltage adjustment device to increase the output voltage, so that the output voltage is stabilized to achieve a stable output.

When it is detected that the output voltage or current exceeds the control range of the regulator. The control circuit will control the output protection device to disconnect the output to protect the electrical equipment. When the output protection device is normal, the output protection device is connected to the output, and the electrical equipment can obtain a stable voltage supply.

Classification

Electronic devices that can provide stable AC power to the load. Also known as AC voltage regulator. For the parameters and quality indicators of AC power supply, please refer to DC power supply. Various electronic devices require a relatively stable AC power supply, especially when computer technology is applied to various fields, the direct power supply from the AC grid without any measures can no longer meet the needs.

AC power supply has a wide range of uses and many types, which can be roughly divided into the following 6 types.①Ferromagnetic resonance type AC voltage stabilizer: an AC voltage stabilizer made of a combination of a saturated choke coil and a corresponding capacitor with constant voltage volt-ampere characteristics. The magnetic saturation type is the early typical structure of this kind of regulator. It has a simple structure, convenient manufacture, a wide range of allowable input voltage, reliable work, and strong overload capacity. However, the waveform distortion is large and the stability is not high. The stabilized voltage transformer that has been developed recently is also a power supply device that uses the nonlinearity of electromagnetic components to achieve voltage stabilization. The difference between it and the magnetic saturation regulator lies in the structure of the magnetic circuit, and the basic working principle is the same. It realizes the dual functions of voltage stabilization and voltage transformation at the same time on an iron core, so it is superior to ordinary power transformers and magnetic saturation regulators.②Magnetic amplifier type AC voltage stabilizer: a device that connects a magnetic amplifier and an autotransformer in series, and uses electronic circuits to change the impedance of the magnetic amplifier to stabilize the output voltage. The circuit form can be linear amplification, pulse width modulation, etc. This type of regulator has a closed loop system with feedback control, so it has high stability and good output waveform. However, due to the use of a magnetic amplifier with greater inertia, the recovery time is longer. Because of the auto-coupling method, the anti-interference ability is poor.③Sliding AC voltage stabilizer: A device that can stabilize the output voltage by changing the position of the sliding contact of the transformer, that is, an automatic voltage-regulating AC voltage stabilizer driven by a servo motor. This type of regulator has high efficiency, good output voltage waveform, and no special requirements on the nature of the load. But the stability is low and the recovery time is longer.④ Inductive AC voltage regulator: A device that stabilizes the output AC voltage by changing the phase difference between the secondary voltage of the transformer and the primary voltage. It is similar in structure to a wire-wound asynchronous motor, and in principle, it is similar to an induction voltage regulator. Its voltage stabilization range is wide, the output voltage waveform is good, and the power can reach hundreds of kilowatts. However, since the rotor is often in a locked-rotor state, the power consumption is relatively high and the efficiency is low. In addition, because copper and iron use more materials, they are less produced.⑤ Thyristor AC voltage stabilizer: AC voltage stabilizer using thyristor as a power adjustment component. It has the advantages of high stability, fast response, and no noise. However, due to damage to the mains waveform, it causes interference to communication equipment and electronic equipment.

⑥Relay type AC voltage stabilizer: A relay is used as an AC voltage stabilizer to adjust the windings of the autotransformer. It has the advantages of wide voltage regulation range, fast response speed, and low production cost. Used for street lighting and relatively remote household use. With the development of power supply technology, the following three new AC power supplies appeared in the 1980s. ① Compensation AC voltage stabilizer: also known as partly adjustable voltage stabilizer. Use the additional voltage of the compensation transformer to connect in series between the power supply and the load. With the input voltage, use an intermittent AC switch (contactor or thyristor) or a continuous servo motor to change the size or polarity of the additional voltage. In order to achieve the purpose of voltage stabilization, the higher part (or insufficient part) of the input voltage is subtracted (or added). The capacity of the compensation transformer is only about 1/7 of the output power. It has the advantages of simple structure and low cost, but the stability is not high. ②Digitally controlled AC voltage stabilizer and stepping voltage stabilizer: The control circuit is composed of logic elements or microprocessors, and the primary turns of the transformer are converted according to the input voltage to stabilize the output voltage. ③ Purified AC voltage stabilizer: It is used because of its good isolation and can eliminate the spike interference from the power grid.

There are problems

Common AC voltage regulators on the market are precision purification type and fully automatic compensation type. The former uses triac technology to achieve the main characteristics of voltage regulation. It has high voltage regulation accuracy, fast response time but narrow voltage regulation range and large waveform distortion. The main problem is: when the capacitive and inductive load of this type of regulator is too heavy, output voltage jitter may occur. At this time, you will see a light bulb. In the periodic flickering and flickering state, the equipment with transformer will produce periodic loud and small noises. This is because the triac used for adjusting the sense is in a partial conduction state. When the input internal resistance is too large, such as the power grid The input transformer capacity is too small and the transmission line is too long> or the output load is too heavy, it will reflect the 3rd and 5th harmonics to the grid, which may cause the voltage of the local grid to be in the period of about 120-200ms and the range is between 190-250V. It is caused by the abnormal output state of the amplitude modulation ringing oscillation type of repeated oscillation.

Micro-power AC voltage stabilizer

Disadvantages of traditional voltage stabilizer

Traditional AC voltage stabilizers use iron cores made of silicon steel sheets. It is large, bulky, and has a lot of power frequency noise during operation, and at the same time it generates heat and is low in efficiency; the traditional AC voltage stabilizer uses the principle of magnetic saturation, and the output sine wave voltage will cause serious distortion.

Micro-power regulator

When the input voltage is within the rated range, no power conversion is necessary. The input voltage directly reaches the output terminal and becomes the output voltage: when the input voltage is When it is greater than the rated voltage. After the voltage cutting circuit, the part of the voltage that is higher than the rated voltage is cut off with a very small proportion. The sine wave voltage converted into rated output is output in parallel with the rated voltage part left after the head is cut off: when the input voltage is less than the rated voltage, the voltage compensation circuit is used to remove the part of the input voltage that is less than the rated voltage When the voltage is compensated with a very small ratio, a compensation voltage is generated by the compensation circuit. This voltage is exactly the difference between the rated voltage and the input voltage, which is superimposed on the input voltage. That is, the output rated voltage is the sum of the input voltage and the compensation voltage.

The biggest feature of the micro-power AC voltage regulator is that it only needs to convert a very small part of the input power to traditional power conversion. The entire output power can be obtained, that is, a large part of the input power does not need to undergo actual power conversion, nor is it necessary to transmit power through a magnetic core transformer or inductor, and directly reach the output end to become output power.

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