One, automatic voltage regulator
This regulator structure is simple, inexpensive, but poor reliability. Because it relies on the movement of carbon brushes (sliding or rolling) to stabilize the voltage, as shown in Figure 2. The control circuit controls the M point to move up and down according to the output setting so that the output voltage meets the requirements of the load. The disadvantages of this circuit are low reliability and slow dynamic response without isolation from interference. Carbon brushes will slowly thin out until they are damaged by constant movement, and the life span will shorten even faster under high humidity. Since it is a mechanical movement, the dynamic response is slow, which will lead to instantaneous voltage rise and fall, damaging the equipment behind.
For example, when the input voltage drops by 15%, that is, 220V down to 187V, in order to ensure that the output is still 220V, M will have to slide up to the N point, the change is 220: 187 = 1.18, at this time, if there is a large inductive loads suddenly download, resulting in the utility voltage suddenly produce a 300V surge, due to the mechanical inertia of the M point and not too late! Move, there will be a high voltage of 354V at the output, which will discharge the UPS battery and burn the UPS input circuit. Conversely, if a large inductive load is suddenly loaded, a 100V depression will also occur, also causing the UPS battery to discharge.
Two, purified power AC voltage regulator
The emergence of this AC voltage regulator is mainly to replace the original electromagnetic compensation type 614 regulator. The principle of this regulator is based on the bi-directional SCR conduction angle and the formation of different equivalent inductance, so that the output of the input changes to compensate for the principle of regulating the principle, the principle is shown in Figure 3.
This power supply is more stable, can reach 0.1%, efficiency is also higher, up to 97%, the output voltage waveform distortion is smaller, can reach 0.2%. This regulator is highly reliable and has the ability to isolate interference. As can also be seen from the figure, the main circuit there is no power tube, are inductors and capacitors and other passive devices, the only semiconductor device or a very high reliability of the bidirectional silicon controlled. However, the disadvantage of this circuit is a narrow range of regulation, generally only adapt to the rated grid voltage ± 10%, the power is not easy to do, which obviously can not meet the requirements of the telecommunications sector, so generally not in the scope of consideration.
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Three, parametric voltage regulator
1, parametric voltage regulator principle of operation
Parametric voltage regulator is the early application of the more common voltage regulator, this is a kind of ferromagnetic resonance according to the principle of regulating the circuit. Its advantage is that the entire circuit does not have a semiconductor component, is composed of a transformer and capacitor circuit, so the reliability is higher, because the parametric regulator is working in the resonant state, so the ability to isolate the interference is stronger. Figure 4 illustrates the principle of operation of the parametric regulator. Since this circuit is used more often and many problems arise, it is described here in more detail. The purpose is to understand its advantages and disadvantages, in order to achieve a more rational use. As shown in Figure 4 for the parametric regulator circuit schematic, the equivalent circuit is an inductor and a capacitor in series.
The capacitance of the capacitor is XC=1/(2fC); inductance of the reactance is XL=2fL
Format: f - utility frequency, HZ
C - capacitance, F
L - inductance of the transformer, H
By the circuit can be seen, the capacitor is the voltage on the UC, UL is the inductance of the voltage on the I is the current through the resistor, capacitance, reactance and capacitance. Current, inductive and capacitive reactance on the voltage difference bit 180, so they are in series when the voltage is the relationship between the decreasing, when the resonance is reached, UC = UL, at this time, XC + XL = O. So it is derived:
f = 〈1〉
This is the resonance point of the LC series circuit, the analysis can be seen from the above three problems:
In the input voltage reaches a certain value, the LC series circuit is the resonance point of the circuit, the voltage is the voltage of the inductor. When the input voltage reaches a certain value, the impedance in the LC series circuit reaches its minimum value, or the current reaches its maximum value, that is, the transformer enters the saturation state, at this time, the voltage on the transformer is basically unchanged, and the output enters the regulator area.
In the resonance point LC and utility frequency to form a fixed relationship, the formula 〈1〉 can also be expressed in terms of angular frequency, that is
ω= 〈2〉
After the point of resonance, if the input voltage continues to rise, then the part of the rise is all added to the capacitor.
2. Advantages of Parametric Voltage Regulators:
A. Parametric voltage regulators work in saturation at the time of resonance, so external disturbances do not cause a change in the saturation current, and so the disturbances are isolated.
B. Since all of the input voltage rise is added to the capacitor, a larger input voltage conversion range is allowed.
C. Since there are no electronic components in the circuit, it is more reliable.
3. Disadvantages of Parametric Voltage Regulators:
A. Since it works in saturation, it consumes a lot of its own power and has low efficiency.
B, because it is resonant in the utility frequency, so the frequency change is very sensitive, once the utility frequency change, it will cause the resonance, once the resonance, its storage in the inductor more than 3 times the reactive power will be released instantly, the formation of thousands of volts of high-voltage pulse transmitted outward, destroying the equipment in its vicinity. A number of UPS fires in a domestic telecommunications sector are caused by it.
C, because it is resonant at the utility frequency, if it is followed by a rectifier load, the harmonics generated by the rectifier will also cause the circuit to stop. According to the test of the relevant scientific research institutions, this time the capacity of the parameter regulator to several times the load behind (typical experiments are 10 times). The above-mentioned telecom sector of the many UPS fires is because of the parametric regulator capacity is too small: for example, a 15KVA parametric regulator with 16KVA UPS, a 30KVA parametric regulator with 40KVA UPS, in dozens of sets of equipment, almost none of them were spared.
D, because in the circuit work is a large amount of internal storage of reactive power, so the input power factor is low, can not make full use of the input utility power, taking up valuable power resources.
Parametric voltage regulator used more successful places are mostly larger capacity or better conditions. So this kind of power supply should be used with caution, especially in the telecommunications sector, such as the higher requirements of the place to beware of hidden dangers.
Four, NPS-type intelligent voltage regulator
This is a new technology, is summarized in the above advantages and disadvantages of several regulators and absorbed the experience of the Delta conversion technology and the development of patented products. This circuit not only adopts the current mature PWM technology, but also combines the Delta conversion technology of UPS.
NPS type intelligent voltage regulator effectively solves the problems of the above regulators:
1, because of the absorption of the experience of Delta transform technology, so it has some of its advantages, such as the input power factor of up to 0.95 or more than the parameter regulator is much higher.
2, high efficiency. From the structure of the circuit can be easily seen, it is a concentration of the advantages of automatic voltage regulator. And reflect the speed, which is unmatched by the automatic voltage regulator.
3, the input and output isolation performance is good, which is the concentration of the parameter regulator and the purification of the advantages of the power supply. Because there is no reactive power storage in the work, so there is no problem of destroying other equipment.
4, high reliability. Due to the combination principle of PWM circuit and magnetic circuit, the structure is lightweight instead of bulky like parametric voltage regulator.
5 、Because of the high efficiency and low loss, the temperature inside the machine is not high, which improves the reliability of the machine.
6, can be intelligent monitoring. The machine left RS232 serial port, you can do remote monitoring.
7, the capacity can be made very large, unlike the purification power supply and parameter regulator as the maximum can only do tens of kilovolt-ampere.
It is with the above advantages, in the power distribution should be the first choice.